Fig 1: Rooting of a basil cutting in water, photo by Jim Farr

Plant propagation is a rewarding practice that allows home gardeners to multiply their favorite plants, save money, and share beloved species with friends and family. Whether you're looking to expand your garden without breaking the bank or preserve a cherished heirloom plant, understanding the basics of plant propagation can open a world of horticultural possibilities. This is the first in a series of articles on propagation. The next article in the series will address grafting methods of plant propagation.

Understanding Plant Propagation

Plant propagation is the process of creating new plants from a variety of sources: seeds, cuttings, bulbs and other plant parts. It falls into two main categories:

•    Sexual Propagation: Involves the use of seeds, resulting from the fertilization of the ovule in flowers. This method produces offspring that are genetically different from the parent plants.

Fig 2: Parts of a flower showing ovule, Image source: USDA Handbook 495.; https://ucanr.edu/sites/btfnp/generaltopics/AnatomyPollination/Pollination1/

Illustration of an insect pollinated peach flower with multiple reduced anthers (dark blue), large pollen grains (orange), smaller stigma (dark purple), long exerted style (light purple), showy petals (pink), and nectaries (yellow).

•     Asexual Propagation (Vegetative Propagation): Involves reproducing plants from stems, roots, leaves, or other vegetative parts, resulting in offspring genetically identical to the parent plant.

Benefits of Plant Propagation

There are a number of benefits with learning the techniques for plant propagation. These benefits include:

•     Saving money: Propagating plants at home reduces the need to purchase new plants. Depending on the rarity of the plant species, this can be a substantial cost benefit.
•     Preservation: Helps in preserving and multiplying one's favorite plants to add to your garden or to provide to others as gifts for their own gardens.
•     Customization: Allows gardeners to select the strongest and most desirable plants from their propagation. Propagating multiple “copies” of a plant allows one to choose the strongest and the most vigorous of the plants to have the best chance of success of growing them in your garden.

Seed Propagation (Sexual Propagation)

University of California Video Demonstrating Seed Propagation: Seed Starting 101

Growing plants from seeds is one of the most common methods of propagation, ideal for annuals, vegetables, and some perennials.

Advantages

• Genetic Diversity: Seeds produce plants with some genetic variations, which can lead to new traits. New, or more valuable and commercially important plants can be produced this way. For example the popular Better Boy Tomato Hybrid was created by crossing two different tomato varieties
• Large Quantities: It's easy to produce many plants at once. Depending on the plant variety, even a small 1 gram packet of seeds can contain hundreds of seeds. This is more than enough for a home vegetable garden with enough left over to donate to neighbors or a local seed exchange.
• Longevity: Seeds can often be stored for future use. Properly stored (typically in cool, dry places), seeds can be fertile for a few years. While seed packets have “expiration dates” for legal reasons, they are still useful and fertile for years after that date depending on the type of seed. Germination rates of older seeds can be checked with the seed germination test: Assessing Seed Viability - The Backyard Gardener - ANR Blogs

Steps for Successful Seed Propagation

1. Seed Selection: Choose high-quality seeds from reputable sources or collect them from healthy plants in your garden. It can be useful to let one's favorite plants “go to seed”, collect the seeds and save them for replanting the following year. In this way one packet of seeds initially can, in principle, be propagated for decades.
2. Seed Preparation: Some seeds, particularly seeds with hard coats, might require scarification (scratching the surface). Examples of seeds that respond well to scarification include morning glories, lupine, sweet peas and nasturtiums. Alternatively some seeds may require stratification (cold treatment) to germinate. Some examples of seeds that are helped by stratification include black-eyed susans, purple coneflowers and many milkweeds. If the seeds have been purchased, carefully review  the planting instructions. If you have collected the seeds, do a little research to find if any pre-planting procedures are required. A good source such as:  The California Garden Web. Another source is the Sunset Western Garden Book.
3. Sowing: Plant seeds in a sterile, well-draining seed-starting mix. Sow at the recommended depth on the seed packet. If the seed packet does not indicate planting depth, a general rule is to plant seeds twice their width.
4. Environment: Maintain consistent moisture and provide adequate, indirect light, for example on a window sill. A warm environment typically encourages germination. While some may use heating mats to provide the heat to the seed trays, often just the temperature indoors (65-70F) near a window is more than sufficient. Be careful not to let seeds dry out before germination. Some seed coats harden if dried and may not germinate at all.
5. Transplanting: Once seedlings develop true leaves, they can be transplanted into larger containers or directly into the garden. The first leaves are not true leaves but cotyledons which provide food for the sprout to initially grow. True leaves are the second set of leaves and are different in shape and size from the cotyledons (seed leaves).  Typically, plants can be planted into larger trays or outside after 2 or 3 true leaves have emerged.

Fig 3: Cilantro showing 2 cotyledons (smooth edges) and 2 true leaves (jagged edges), photo by Paula Pashby, https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=46056

Asexual Propagation Methods

Asexual propagation produces clones of the parent plant, ensuring the new plants retain all the desirable characteristics. Some plants can be easily propagated from cuttings and in fact that may be the preferred method of propagating. Many herbs such as basil are examples of this. A cutting from a basil plant, placed on a windowsill in a cup of water, will produce roots in days or weeks at the most.

1. Propagation by Cuttings (Asexual Propagation)

University of California Video Demonstrating Propagation from Cuttings: Cloning Garden Plants

Stem Cuttings – when propagating from stem cuttings, it is recommended to choose stems that are in a certain stage of wood. Below are examples of three stages of wood:

Types of stem wood:

•  Softwood Cuttings: Also known as “herbaceous” wood, taken from new, soft growth in spring or early summer.
•  Semi-Hardwood Cuttings: Sometimes referred to as “green wood”, taken from partially matured wood in mid to late summer before the wood is fully mature and hardened. These are less flexible than soft wood but do not snap to produce sharp edges like hardwood cuttings. They produce smooth edges when snapped.
•  Hardwood Cuttings: Taken from dormant, mature stems in late fall or winter. Hardwood is the hardest form of wood and usually brown in color vs. the green of semi-hardwood.

For examples of softwood , semi-softwood and hardwood see page 16 of University of California Presentation: Asexual Plant Propagation

Procedure:

1. Selection: Choose healthy, disease-free stems. Soft yellow or black stems or mushy black areas are signs of unhealthy stems.
2. Cutting: Make a clean cut just below a node (where leaves attach). The best type of knife are razor blade knives that have been rubbed with alcohol to sanitize them. See Propagation from Cuttings for examples of where to make cuts.
3. Preparation: Remove lower leaves and dip the cut end in rooting hormone to encourage root development. Rooting hormones can be purchased online or from any nursery. Typically, they are in powder or liquid form. Powder is preferred since it will stick to the cut area better.
4. Planting: Insert the cutting into a pot filled with moist, well-draining medium like perlite or sand mixed with peat moss. Make a small hole first with a pencil or small stick to put the stem in. Pushing the stem directly into the soil will remove some of the rooting hormone on the tip. For the best results soil should be sterilized in an oven. To sterilize soil, heat the soil in an oven at 180 F for 30 min or get the temperature up to 212 F where sterilization is immediate.
5. Aftercare: Keep the medium moist and place the pot in a warm area with indirect light. It is a good idea to cover the pot loosely with plastic wrap or some other covering to keep moisture in and prevent the soil from drying out.

Fig 4: Examples of potted cuttings from a fern and purple sage, photo by Jim Farr

Leaf Cuttings

See University of California youtube video: Mastering Stem and Leaf Propagation starting at 37 min.

•     Suitable for plants like African violets and succulents.
•     Procedure: 
  • Cut a healthy leaf with a short piece of stem. Examples of what this looks like are in the above video.
  • Insert the stem into the growing medium. This is similar to above for stem cuttings.
  • Maintain high humidity until roots develop. Again, plastic wrap or some other covering that will let light through is useful to keep the soil moist and prevent it from drying out.

Root Cuttings

See: Propagation from Root Cuttings

• Used for plants like phlox and horseradish.
• Procedure:
• Dig up a healthy plant and cut 2–3-inch sections of thick roots. As above, cutting tools should be sanitized and sharp.
• Place horizontally in the growing medium and cover lightly. Soil should be sanitized (see above) ahead of time to give the best chance of success.

2. Layering

See University of California youtube video: Mastering Stem and Leaf Propagation starting at 60 min

Layering involves rooting a part of the parent plant while it is still attached. Essentially, the branch of the rooted plant is bent down and covered with soil. Roots form from the branch covered in soil. Examples of some plants that can be propagated this way include climbing roses, rhododendrons and azaleas.

Simple Layering

    Procedure:

1. Bend a low-growing, flexible stem to the ground. If you are bending rose branches, be sure to wear heavy gloves to prevent skin punctures.
2. Scrape the stem slightly to encourage rooting.
3. Bury a portion of the stem in soil, leaving the tip exposed.
4. Secure with a U-shaped pin if necessary. U shaped pins that are used to hold down irrigation lines (sometimes referred to as garden staples) are very useful here.
5. After roots develop, sever the new plant from the parent. Once the rooted stem has roots that are at least several inches long, the stem can be cut and potted like above for propagation from cut stems.

Air Layering

Simple and Air Layering

•     Suitable for houseplants and woody shrubs. Examples of plants suitable to this method of propagation include: camelias, acers, daphnes, jasmine and viburnum.

•     Procedure:

1. Select a healthy stem and make an upward 1-inch cut. See picture for example.
2. Insert a toothpick to keep the cut open.
3. Apply rooting hormone to the wound. Follow the instructions for use of the rooting hormone above.
4. Wrap moist sphagnum moss around the cut area and cover with plastic wrap. See Simple and Air Layering
5. Once roots are visible, cut below the rooted area and plant. Plant per the instructions above for rooting cut stems.

3.  Division

See University of California youtube video: Mastering Stem and Leaf Propagation starting at 55 min.

Division is ideal for perennials and grasses that form clumps and also bulbs. Many types of bulbs over time will form large clusters of bulbs. Eventually some of the bulbs will stop sprouting when the clusters get too large. It is best to break up these large clusters and then plant the separate bulbs.

•     Procedure:

1. Dig up the entire plant or bulb cluster
2. Gently separate the plant into sections, ensuring each has roots and shoots. Some bulb clusters may be difficult to separate and a garden knife is sometimes helpful. Be careful and always wear thick gloves.
3. Replant the divisions promptly at the same depth they were growing before.

Fig. 5: Bearded Iris before and after division, photo by Patsy Babbitt

4.  Grafting

Grafting is the propagation method that involves taking cuttings (called scions) and attaching them to a root stock or existing stem. This is often considered a more advanced technique and will be addressed in the second article in this series.

Conclusion

Propagating plants at home is a fulfilling endeavor that enhances your gardening experience, saves you money and provides an opportunity to grow unusual varieties not readily available in nurseries. By mastering these propagation techniques, you not only expand your garden but also contribute to plant conservation and biodiversity.  So, roll up your sleeves, gather your tools, and start multiplying your garden's beauty one plant at a time.

References:

General Propagation Methods including cuttings, layering and division

https://ucanr.edu/sites/ucmgnapa/files/81929.pdf

Propagation from Cuttings:

https://marinmg.ucanr.edu/CARE/PROPAGATING/Cuttings/

Layering Techniques:

https://marinmg.ucanr.edu/CARE/PROPAGATING/Layering/

Asexual Plant Propagation:

https://ucanr.edu/sites/EDC_Master_Gardeners/files/175642.pdf

Plant Propagation Books:

1. American Horticultural Plant Society - Plant Propagation by Alan R. Toogood
2. The Plant Propagator's Bible: A Step by Step Guide to Propagating Every Plant in Your Garden by Miranda Smith

Want to learn more?

This blog post is brought to you by the Help Desk of the UC Master Gardeners of Alameda County.  Subscribe to our blog! 

Have a gardening question? We'll Help. You can reach us by:

• Emailing acmg@ucanr.edu. Please include a photo of the problem, if you can, plus your name, phone number, city and a description of the problem.

• Using our online form.

• By phone, during our office hours, 10 am to noon Wednesday and 11 am to 1 pm Thursday: 510-670-5645. At other times, please leave a message and we'll return your call during our office hours.

• In person at our Hayward office, during our office hours, only by appointment. Office is located at 224 West Winton Ave, Room 134, Hayward 94544.

Spotted Lanternfly on Tree of Heaven, by Richard Gardner, Bugwood.org

“The one tree in Francie's yard was neither a pine nor a hemlock.  It had pointed leaves which grew along green switches… and made a tree which looked like a lot of opened green umbrellas. Some people called it the Tree of Heaven. No matter where its seed fell, it made a tree which struggled to reach the sky. It grew in boarded-up lots and out of neglected rubbish heaps and it was the only tree that grew out of cement. It grows lushly . . .

A Tree Grows in Brooklyn, Betty Smith

Has Tree of Heaven Become the Tree of Hell? 

This quote captures well the reasons why Tree of Heaven (ToH) was so popular and is so widespread, as well as the reason why it it's now creating serious problems for both our native forests and our agricultural industries, by spreading rapidly and harboring dangerous insect pests.  

Tree of Heaven (Ailanthus altissima) is an invasive plant species intentionally brought to the U.S.  It was first introduced in the Philadelphia area in the late 1700s as a botanical curiosity; it is native to China and Taiwan, where it was used medicinally and to feed silkworms. Tree of Heaven (ToH) was later brought to the West Coast in the 1850s by immigrants as a reminder of home.

ToH was widely adopted throughout the 1900s because it was unusual, fast-growing, and tolerant of poor soil and poor air quality. In addition to being traded among individuals, it was widely cultivated by the nursery trade and was even distributed by the USDA.  In the early 20th century, it began to lose popularity because of its unpleasant odor, tendency to sprout from its roots and overall “weediness.” As Betty Smith noted, it's frequently found growing out of cracks and crevices of patios and sidewalks, close to foundations and out of stone walls.

Tree of Heaven with flowers. Photo by James H. Miller, USDA Forest Service, Bugwood.org (650 x 450 px)

Tree of Heaven has reached at least 45 states and is well established in California urban, suburban, agricultural, riparian and disturbed forested areas and along transportation corridors. As of 2018, it was found in 39 of California's 58 counties.  So far in California, it has not been found in undisturbed remote wild areas.

Tree of Heaven is considered an invasive pest in much of the US, Europe and Australia, including in California, where it is classified as a noxious weed.  Tree of heaven is subject to an external quarantine, and may not be brought into California.  

Why worry about Tree of Heaven?

ToH has many of the drawbacks of invasive plants generally - it harms native plants by crowding them out and taking the water and other resources they need, reduces habitat needed by native pollinators and other native wildlife, and can change an area's ecology, particularly streambed areas. ToH brings its own specific harms too:

• ToH is a preferred host to two troublesome invasive insects threatening California:  Spotted Lanternfly and the Brown Marmorated Stink Bug.  Both have the potential to do major damage to our agricultural crops.

• Toxics in decomposed leaves from Tree of Heaven inhibit the growth of other nearby plants, allowing ToH to take over areas even faster.

• Tree of Heaven impacts human health because it produces a lot of pollen, aggravating allergies.  Direct contact with the tree can cause skin irritation. If broken skin is exposed to sap, in rare cases, much more serious problems can occur.

• To make all of this more problematic, Tree of Heaven is hard to remove - you can't rid yourself of it by just cutting the tree down.

What Californians can do AND SHOULD NOT DO to help manage Tree of Heaven

• Don't plant Tree of Heaven and educate your friends and neighbors to avoid planting it as well.  If you suspect a tree on your property to be Tree of Heaven, confirm its identification -TOH has look-alikes.  California natives that look like ToH include black walnut, sumacs, ash, hickory, butternut and pecan. 

• Some helpful ID tips: 
• TOH leaves are pinnately compound, which means a central stem within the leaf with multiple leaflets on both sides. The leaf is one to 4 feet long with 10 to 40 leaflets (image A)
• The scar on the main trunk when a leaf is removed is heart-shaped. (Image B)
• The edges of ToH leaves are smooth, but near the base of each leaflet, there are one or two bumps - called glandular teeth.  All of the natives listed above have completely serrated leaflet edges. (Image C) 
• TOH bark, crushed leaves and male flowers emit an unpleasant odor, sometimes compared with cat urine or burnt peanut butter
• The bark of a mature tree resembles the skin of a cantaloupe. (Cover Image.)  
• Video with more ID tips.   
  

  Tree of Heaven, ID Tips, by Cindy Kron, UCIPM
• If you have identified a Tree of Heaven, one approach is to monitor it regularly for Spotted Lanternfly and report any sightings. Should Spotted Lanternfly be found in the state or your region, monitoring may require trapping at that point. 

• Another approach is to remove the tree.  Removing the Tree of Heaven requires specific techniques.  ToH cannot be effectively managed by cutting or mowing alone.  Cutting alone may just spread the plant. When cut, a  Tree of Heaven responds by sprouting exuberantly from its roots, and these sprouts can be up to 50 feet from its parent tree.

• If you are going to remove a Tree of Heaven, be sure to wear long sleeves and gloves to protect yourself when you work near it, because contact with ToH can cause skin irritation. If broken skin is exposed to sap, in rare cases, much more serious problems can occur.If you decide to remove a Tree of Heaven, the recommended treatment protocol is to apply a systemic herbicide to the plant between July and mid-October, when carbohydrates are being sent to the root system, followed by cutting the tree after symptoms of herbicide damage appear, and no sooner than 30 days after application.

• The herbicide may be applied on the foliage on small and/or scattered trees or on the low growth of larger ones.  Then follow up with a bark or hack-and-squirt application for larger stems.  If doing hack and squirt, make downward angled cuts spaced around the tree between ankle and breast height, making sure to leave living bark between the hacks so the tree can transport the pesticide down to the roots.  Treating a ToH stump with herbicide is not effective,

• Applying the herbicide at a different time of year may kill the foliage above the ground, but will fail to kill the roots. Seedlings can be pulled out by the roots, but it is uncommon to see seedlings in California. ToH rarely propagates by seed here, unlike further East. With larger trees, trying to remove the root system will be ineffective.  

• After an established ToH is removed, it's recommended to continue to monitor, because additional treatments may well be required in the second year.  

Spotted Lanternfly - a Best Buddy of Tree of Heaven

As discussed above, the invasive Tree of Heaven is a preferred host of Spotted Lanternfly (SLF).  The Spotted Lanternfly (Lycorma delicatula) is native to China, and entered the US inadvertently.  SLF was first located in the US in Pennsylvania in 2014, and is already a significant problem in the Eastern US.  It has spread quickly and widely in the Northeast and Midwest, and has been spotted as far north as upstate NY, as far south as North Carolina, as far east as Massachusetts and as far west as Iowa, spurring appeals to the public to "Squish It!.

Michigan Billboard, used with permission

California is definitely at risk from Spotted Lanternfly.  One scientific model found that, without preventative management, SLF has a high probability of reaching the grape-producing counties of California by 2033.  In 2021 an external quarantine was imposed prohibiting entry into California of Spotted Lanternfly, its host plants and many other objects coming from areas with known SLF.   As of this writing, no live SLF has been found in California, but a viable egg mass was found on a shipment of wood at a Truckee inspection point in June 2024.  Even after the load was washed, on re-inspection over 900 eggs were found.  

Why worry about SLF?

• California has a lot to lose if Spotted Lanternfly reaches us - grapes, one of our most valuable agricultural products, are a preferred host. Other agricultural SLF hosts include apple and stone fruit, and it also affects ornamental trees.  It's very possible that additional plants that we grow in California are susceptible, but are not yet identified because they don't grow in areas currently affected by SLF.

• SLF harms plants by feeding on their phloem, the liquid that transports sugars, proteins and other molecules up and down the plant. This feeding weakens and stresses the plants, can lead to reduced cold hardiness, lack of bloom or fruiting.  SLF also produces honeydew, a sweet sticky substance exuded by several insects.  This builds up and encourages the sooty mold fungus, which interferes with photosynthesis and can stunt plant growth.  SLF can kill grapes and Tree of Heaven.

• ThepotentialeconomicharmfromSLF infestation includes:
  • Increased production costs for crops.
  • Decreased yields.
  • Infested crops may become unsellable - only a small amount of sooty mold on grapes is enough for a buyer to reject them.
  • Export problems - areas without Spotted Lanternfly (which include Europe, Australia, Mexico and Canada) may reject exports of our vulnerable crops.

So there are plenty of reasons to be concerned about SLF and to work to prevent its becoming established in California.

What Californians can do to help manage the Spotted Lanternfly threat.

Keep a lookout:  Early detection and treatment will help protect our agricultural industries.  It is far easier and less expensive to deal with an invasive pest before it establishes itself in the area.

• What does Spotted Lanternfly look like? Eggs, juveniles and egg masses are distinctive in appearance.

• Egg masses vary in size, but typically are about an inch long by 3/4 inch wide.  Freshly laid egg masses appear to be coated with a white substance. As they age, the egg masses look as if they are coated with gray mud, which eventually takes on a dry and cracked appearance. Very old egg masses may look like rows of 30 to 50 brown seed-like structures aligned vertically in columns.

SLF Eggs, various stages, Emelie Swackhamer, Penn State University, Bugwood.org

• Young are called nymphs and have four stages, or instars.  The first, second and third stages are black with white spots, and increase in size as the stages progress.  The fourth stage becomes distinctly red, with patches and black and white.

• Adults are about an inch long and ½ inch wide at rest. SLF has a black head and black legs, with a yellow abdomen. There are two sets of wings. The front of the forewings are gray with a pinkish tinge, spotted with black.  The back of the forewings have a gray and black brick pattern.The hind wings are red and black, and are exposed only when the insect is in flight, startled or dying.
  

  Spotted Lanternfly Collage: Eggs, Young and Adults, by UC IPM

Where to Look

• Egg masses can be anywhere outside, and are frequently found on inanimate objects, such as lawn furniture, kiddie pools, toys, and miscellaneous wood, as well as trees and other plants.

• Look for adults on trees and bushes.  Look especially on their preferred hosts:  Tree of Heaven and grapes.

Report What You See

• If you see a Spotted Lanternfly, try to collect it and put it in a sealed container or freeze it.  If you can't collect it, take as good a photo as you can.  Keep a note of exactly where you found it.  

• Report your sighting to your local county Agricultural Commissioner's office right away. In Alameda County,  call:  (510) 670-5232 OR

• ReportyourfindtotheCDFA hotline: 
  • Phone Hotline: 1-800-491-1899 or 
  • Online at  cdfa.ca.gov/plant/reportapest

Working together, the appropriate California agencies, the UC Master Gardeners and Californians at large can help manage the Tree of Heaven and Spotted Lanternfly invasives.  

More Information:

UC IPM Tree of Heaven Overview

UC IPM Spotted Lanternfly Overview

Calif Dept of Fish and Wildlife:  Invasive to Avoid:  Tree of Heaven

UC Cooperative Extension Sonoma: Spotted Lanternfly

UC Cooperative Extension Sonoma:  Invasive Tree of Heaven - Host for Invasive Pests

Fresno Master Gardeners:  Guidelines for successful tree-of-heaven removal

eLearning course on Spotted Lanternfly in California

Want to learn more?

This blog post is brought to you by the Help Desk of the UC Master Gardeners of Alameda County.  Subscribe to our blog!

Have a gardening question? We'll help. You can reach us by:

• Emailing acmg@ucanr.edu. Please include a photo of the problem, if you can, plus your name, phone number, city and a description of the problem.
• Using our online form.
• By phone, during our office hours, 10 am to noon Wednesday and 11 am to 1 pm Thursday: 510-670-5645. At other times, please leave a message and we'll return your call during our office hours.
• In person at our Hayward office, during our office hours, only by appointment.

Cross-section of soil contains billions of beneficial microbes - Photo courtesy of the Natural Resources, https://ucanr.edu/sites/Nutrient_Management_Solutions/Management_Goals/Build_Soil_Health/Conservation Service

When we think of gardening, our minds often drift to the vibrant colors of blooming flowers, the lush green of growing vegetables, and the satisfaction of a bountiful harvest. However, beneath the surface of your garden lies a hidden world that is just as crucial to the success of your plants: soil microbes. These tiny organisms, invisible to the naked eye, play a vital role in maintaining healthy soil and, consequently, thriving plants. Let's delve into the fascinating world of soil microbes and understand their importance in home gardens.

What Are Soil Microbes?

Soil can be rich in microbes by Amanda Hodson, Soil Food Webs, https://mgeldorado.ucanr.edu/files/250718.pdf

Soil microbes include a variety of microorganisms such as bacteria, fungi, protozoa, and nematodes. These microscopic organisms form a complex and dynamic ecosystem in the soil, interacting with plant roots, organic matter, and each other. Each type of microbe has its unique function, contributing to the overall health and fertility of the soil.

The Benefits of Soil Microbes in Home Gardens

1. Nutrient Cycling and Availability

   

   Beans and other legumes have bacteria that take nitrogen from the air and make nitrogen nodules – photo courtesy of University of California, https://news.ucr.edu/articles/2023/07/24/study-improves-understanding-how-bacteria-benefit-plant-growth
          Soil microbes are essential for nutrient cycling, a process that transforms nutrients into forms that plants can easily absorb. For instance, certain bacteria convert nitrogen from the air into a form that plants can use, a process known as nitrogen fixation. Fungi, particularly mycorrhizal fungi, form symbiotic relationships with plant roots, extending their reach and enhancing nutrient uptake, particularly phosphorus.

2. Soil Structure and Health

   Microbes contribute to the formation of improved soil structure. A well-structured soil has better aeration, water retention, and root penetration capabilities. This, in turn, leads to healthier plant growth. Fungal hyphae, the thread-like structures of fungi, bind soil particles together, creating a stable and porous soil environment.

3. Disease Suppression

   A diverse and balanced soil microbial community can help suppress soil-borne diseases. Beneficial microbes compete with pathogenic (disease-causing) organisms for space and resources, reducing the likelihood of diseases taking hold. Some microbes produce natural antibiotics that inhibit the growth of harmful pathogens, providing an added layer of protection for your plants.

4. Organic Matter Decomposition

   Soil microbes are decomposers, breaking down organic matter such as dead plants and animals into simpler compounds. This decomposition process releases nutrients back into the soil, making them available for plant uptake. Composting, a popular practice in home gardening, relies heavily on microbial activity to convert kitchen scraps and yard waste into rich, fertile compost.

5. Enhanced Plant Growth and Resilience

   The presence of beneficial soil microbes can enhance plant growth and resilience. Plants with healthy microbial communities in their root zones tend to grow more vigorously and are better equipped to withstand stressors such as drought, pests, and diseases. This symbiotic relationship between plants and microbes creates a robust and thriving garden ecosystem.
   

   The soil food web from presentation by Amanda Hodson, Soil Food Webs, https://mgeldorado.ucanr.edu/files/250718.pdf

How to Foster a Healthy Soil Microbial Community

1. Minimize Soil Disturbance

   Tilling and digging can disrupt soil structure and harm beneficial microbes. Practice minimal soil disturbance to maintain a stable environment for microbial activity.

2. Add Organic Matter

   Regularly incorporate organic matter such as compost into your garden soil. Organic matter serves as food for microbes, promoting their growth and activity.

3. Avoid Chemical Overuse

   Limit the use of chemical fertilizers and pesticides, as they can harm beneficial microbes and disrupt the soil ecosystem. Choose organic or slow-release fertilizers and natural pest control methods instead.

4. Plant Diversity

   Cultivate a variety of plants in your garden. Different plants exude different compounds through their roots, attracting diverse microbial communities and promoting a balanced soil ecosystem. Here is more information: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6992662/

5. Maintain Proper Soil Moisture

   Ensure your soil is well-drained but retains adequate moisture. Microbes require water to thrive, so maintaining proper soil moisture levels is crucial for their activity.

Conclusion

Soil microbes are the hidden, unsung heroes of home gardens, working tirelessly beneath the surface to ensure the health and vitality of your plants. By understanding their importance and fostering a supportive environment, you can enhance the productivity and sustainability of your garden. Embrace the power of soil microbes, and watch your garden flourish like never before. Happy microbes make happy gardens!

References:

Soil Basics: https://ucanr.edu/sites/soils/Soils_101/
Microbes in Your Soil: https://ucanr.edu/sites/CalaverasCountyMasterGardeners/files/203582.pdf
Get the Dirt on Soil Microbes:
https://caes.ucdavis.edu/news/articles/2017/03/get-the-dirt-on-soil-microbes

Want to learn more?

This blog post is brought to you by the Help Desk of the Master Gardeners of Alameda County.  Subscribe to our blog!

Have a gardening question? We'll help. You can reach us by:

• Emailing acmg@ucanr.edu. Please include a photo of the problem, if you can, plus your name, phone number, city and a description of the problem.
• Using our online form.
• By phone, during our office hours, 10 am to noon Wednesday and 11 am to 1 pm Thursday: 510-670-5645. At other times, please leave a message and we'll return your call during our office hours.
• In person at our Hayward office, during our office hours, only by appointment.
  

  Beans and other legumes have bacteria that take nitrogen from the air and make nitrogen nodules – photo courtesy of University of California, https://news.ucr.edu/articles/2023/07/24/study-improves-understanding-how-bacteria-benefit-plant-growth

(Case study: The Mediterranean Fruit Fly in Alameda County, Sept. 2024)

Mediterranean fruit fly is considered to be the most destructive agricultural pest in the world. (Photo by 5193024-Medfly, Florida Division of Plant Industry, Florida Department of Agriculture and Consumer Services, Bugwood.org)

 Invasive Species are either here or on their way.

Invasive species threaten California's home gardens and more importantly California's agriculture, ecology and environments.  Invasive species are non-native (or exotic) species whose introduction is likely to cause economic or environmental harm, or harm to human health. There are infestations that require an immediate and rapid response to eradicate the pest before it can become established. The discovery of the one wild mated female Mediterranean fruit fly in Alameda County prompted such a response, showing the high priority of eradicating what is considered to be the world's most destructive agricultural pest before it can establish itself in California.

Some other invasives are already established in California, and some we are on the watch for, knowing there is a high likelihood of them being detected in California. Some are present in Southern California and we are on alert for them making their way to our counties here in Northern California.

This blog series focuses on a few invasives, mostly plants and insects, but there are also invasive fish, mammals and birds. The invasive exotic (non-native) fruit flies – Caribbean, Guava, Mediterranean, Melon, Mexican, Olive, Oriental, Peach and others – are all serious threats to home gardeners and the agricultural economy.  Asian Citrus Psyllid and Huanglongbing Disease, Invasive Shothole Borers, Tree-of Heaven, Brown Marmorated Stinkbug, European Grapevine Moth, and Spotted Lanternfly are just some of the invasives that California is monitoring for their appearance or spread in California.

Invasive Plants and Pests: Major Threats to California's Agriculture, Home Gardens and Environments

Olive fruit fly poses a severe economic threat for the state’s commercial olive growers. (Photo by 5430505 olive fruit fly, Lorraine Graney, Bartlett Tree Experts, Bugwood.org)

In some cases, non-native plants and pests become serious pests, while others blend in and do not cause noticeable problems. California is on the lookout for non-native invasive species that result in economic costs in order to:

• control invasives
• reduce rate of spread
• inspect agricultural products to prevent accidentally moving invasives to new areas.

In addition, financial costs to farmers to control pests, often with pesticides, results in higher food prices for the consumer. The economic threat can be to agriculture generally or to growers of specific crops such as grapes or citrus. 

There are also additional risks to the environment:

• Upset to the ecosystem, crowding out native plants and animals
• Greater chance of wildfires, with greater intensity
• Depletion of the water table
• Invasive plants can be preferred hosts for invasive pests (These non-native plants provide food and shelter particularly suitable for invasive pests, promoting uncontrolled population growth. The California environment lacks the predators from their native habitat that would normally keep the pest population manageable.)
• There are costs to ornamental trees dying because of pests and then needing to be removed

In California, at least $3 billion is spent annually on eradicating invasive pests, according to the University of California at Riverside.

How Invasives Arrive and Become Established

Invasive species are spread by human activity, often unintentionally. Now, with the ease of travel nationally and internationally, there is greater potential for exotic or non-native species to arrive unnoticed. Rapid transportation makes it likely that accidental hitchhikers survive long distance travel. Ornamental plants, along with hitchhiking insects, can become invasive after escaping into the wild. Insects can be unintentionally transported and spread to new areas when they or their eggs are on things, such as plants, plant material, vehicles, wood, that are moved. The diversity of climates and habitats in California can result in the right combination for exotic organisms to become established.

Invasive Plants Originating from the Nursery Industry

Tree-of-heaven, an invasive, was once a popular ornamental tree commonly found in nurseries. (Photo by 5541618 tree-of-heaven, Richard Gardner, Bugwood.org)

The California Invasive Plant Council (Cal_IPC) has a list of non-native invasive plants that either have already impacted natural areas or are at high risk of becoming invasive, damaging wildlife habitat, degrading food and water supply and more.  Many of these plants were intentionally introduced by the nursery industry as ornamental landscape species. According to the UC IPM Pest Note on Invasive Plants, about 60% of the species listed were intentionally introduced, and most of that 60% came through the nursery industry as ornamental landscape species.

Management of Invasives

The Mediterranean fruit fly (the medfly) is an example of how invasives can be managed. In September 2024, one mated female was found in Alameda County. This fly is known to target over 250 fruits and vegetables. The fly causes damage when females lay eggs in the produce.  The eggs hatch into maggots that burrow through the produce making it unfit for sale or consumption. The Medfly is considered to be highly invasive but is not yet established in California. It has the potential to have a devastating effect on agriculture and home gardens,so there will be a concerted, coordinated plan to eliminate the Medfly.

Proactive Management - Quarantines, Inspection, Bans on Imports or Sales

Management of invasive species may be proactive, focusing on the exclusion of the pest. Exclusion management uses quarantine laws, the inspection of imports for hitch-hikers, and the banning of import or sale of certain plant and animal species.  If detected at a very early stage of invasion, the goal will be to eradicate the pest, as it is currently being done with the fruit flies, including the Mediterranean fruit fly pictured below.

Mediterranean fruit fly causes quarantine in Alameda County, September, 2024 (Photo by 1317084 Mediterranean fruit fly, USDA ARS Photo Unit, USDA Agricultural Research Service, Bugwood.org)

The Mediterranean fruit fly  - Proactive Management in Action

The September 2024 discovery of a single mated female Mediterranean fruit fly in Fremont resulted in a quarantine of 71 square miles in southern Alameda County, now expanded to 83 square miles. The California Department of Food Agriculture (CDFA) announced the quarantine, the first in Alameda County since 1981. View the quarantine map. The quarantine affects growers, wholesalers and retailers of susceptible fruit, as well as local residents.

An invasive fruit fly quarantine , what does it mean for home gardeners?

• Check to see whether you are in the quarantine area
• Home gardeners are encouraged to consume their own fruits and vegetables, and not move produce from their properties.
• Do not compost your fruits and vegetables.
• When disposing of produce, double-bag the waste and put it into the trash instead of the green waste bin.
• Don't let ripe produce fall to the ground.
• Inspect your garden for signs of invasive fruit flies or maggots.
• If you think your fruits and vegetables may be infected with fruit fly larvae, call CDFA's Pest Hotline (800) 491-1899 or reportapest@cdfa.ca.gov

How else can Californians help with the Medfly?

• The majority of fruit flies and other invasives are found in urban and suburban communities.  The most common pathway for these invasive species to enter our state is by “hitchhiking” in fruits and vegetables brought back illegally by travelers as they return from infested regions of the world.
• To help protect California's agriculture and natural resources, CDFA urges travelers to follow the Don't Pack a Pest program guidelines (https://www.dontpackapest.com/)
• Buy fruit trees and vegetable plants from licensed California nurseries.

What else is being done to eradicate the Medfly?

In the case of the Mediterranean fruit fly, the plan to eliminate the pest uses the standard Medfly program by the CDFA and is the safest, most effective, and most efficient response program available. Sterile male fruit flies will be released in a 39-square-mile area around the infestation at a rate of 250,000 male fruit flies per square mile per week. The sterile males mate with the female fruit flies but do not produce offspring. The goal is to leave no new fruit flies to replace the wild ones as they reach the end of their short lives.

In addition, an organic form of Spinosad is being used to treat properties within 200 meters of the detection site to reduce the population of fruit flies. Fruit removal will take place on properties within 100 meters of those with mated females, larval detections and multiple adult detections.

Reactive Management - Do Nothing, Cultural, Chemical, Biological Controls; or Integrated Pest Management (IPM)

Another approach is reactive management where exclusion and eradication is impossible. This is used when an invasive species has successfully invaded and high populations are now spread over large areas.

Options include:

• do nothing, where there is no management plan in effect, as is often done with invasive weeds in national, state or county parks
• use cultural controls, such as crop rotation, use of plants resistant to specific plant disease, or mulching to promote growth of beneficial organisms
• use chemical controls (pesticides), which are often expensive, need repeated applications, and they may leave pesticide residues leading to human safety concerns
• use biological controls, which involve the use of natural enemies (predators, parasitoids and pathogens) of the invasive species
• use integrated pest management which combines a variety of control strategies to control an invasive pest.

    
The Big Three Protecting California's Food Supply with Information, Detection, and more …

Mexican fruit fly infests many fruits and vegetables, particularly citrus and mango (Photo by 2089 Mexican fruit fly laying eggs, Jack Dykinga, USDA AGricultural Research Service, Bugwood.org)

The US Department of Agriculture, the California Department of Food and Agriculture and the Agricultural Commissioners of each California county work together. They have services that gather and provide information on invasives, provide detection services and coordinate management of invasives.

1)  U.S. Department of Agriculture

National Invasive Species Information Center (NISIC) was established in 2005 at the U.S. Department of Agriculture (USDA's) National Agricultural Library (NAL) to meet the information needs of users, including the  National Invasive Species Council (Council or NISC).

The NISC provides "the high-level vision and leadership necessary to sustain and expand Federal efforts to safeguard interests of the United States by preventing, eradicating, and controlling invasive species, as well as restoring ecosystems and other assets impacted by invasive species."

invasivespeciesInfo.gov  is managed by NISIC at NAL. This site serves as a gateway to invasive species information, including federal, state, local and international sources.  It provides selected U.S. and International resources from agencies and organizations with an interest in the prevention, control, or eradication of invasive species, organized by geography.

2)  California Department of Food and Agriculture

CDFA Plant Health and Pest Prevention - Border protection, Pests Detection and Exclusion, Quarantine Information and more

The California Department of Food and Agriculture (CDFA) has Plant Health and Pest Prevention Services to protect California's food supply from exotic pests. https://www.cdfa.ca.gov/plant/ 

CDFA early detection and eradication projects

It also has pest detection/emergency projects for the early detection and prompt eradication of serious agricultural pests from California.  https://www.cdfa.ca.gov/plant/PDEP/

CDFA list of invasives

There is a list of insect pests and plant diseases targeted by the CDFA detection and emergency projects. The list includes Asian Citrus Psyllid and plant disease Huanglongbing (HLB), invasive fruit flies,  Spotted Lanternfly 

https://www.cdfa.ca.gov/plant/PDEP/target_pests.html

3)  The Alameda County Department of Agriculture/Weights and Measures  (Agricultural Commissioner of Alameda County)

Agricultural Commissioner of each county is charged with the protection of California agriculture, the protection of the environment as well as protection of the public's health and safety. Nearly all of California's counties have combined the offices of the Agricultural Commissioner with the County Sealer of Weights and Measures. In Alameda County, that office is the Alameda County Department of Agriculture/ Weights and Measures.

The Alameda County Department of Agriculture / Weights and Measures is an essential part of the defense for California agriculture and the environment against the invasion of exotic pests. Its programs include pest exclusion and pest detection.

What Can Californians and the Home Gardener Do?

Innocent sharing or movement of infected plants or other materials can have long-term effects costly to all Californians.  Here are some suggestions from UC Riverside Center for Invasive Species Research for how you can help.

• Select garden plants that are not likely to be invasive. Check with local garden center or online with https://plantright.org/about-invasive-plants/better-plants/  Buy locally from a reputable source.
• Do NOT move soil and firewood from one area to another.  Often soil and firewood contain hitchhiking species of insects, bacteria, fungi or worms.
• Do not release pets, aquatic animals or plants into the wild.
• Wash and clean outdoor gear, boats, and vehicles before returning home to reduce the likelihood of unwanted hitchhikers moving into new areas.
• Be supportive of the inspections, quarantines, bans on sales or imports and other actions of the CDFA.
• Be supportive of the pest detection efforts of the Alameda County Department of Agriculture (Agriculture Commissioner's office) by allowing insect survey traps on your property.
• Keep a Lookout. Learn more about the invasive pests and diseases and be on the watch for pests that have a high likelihood of moving into California or spreading into new areas within California.
  • https://ipm.ucanr.edu/invasive-and-exotic-pests/
  • https://www.iscc.ca.gov/publications/ISCC_trifold_LR.pdf
• Report Sightings. Be a “citizen scientist”.  Call California's Pest Hotline (800) 491-1899 or contact your local Agricultural commissioner. (510) 670-5232

Resources:

Alameda County Department of Agriculture / Weights and Measures
(Agricultural Commissioner of Alameda County)
Pest Exclusion https://www.acgov.org/cda/awm/agprograms/pestexclusion/index.htm
Pest Detection https://www.acgov.org/cda/awm/agprograms/pestdetection/index.htm

California Department of Food and Agriculture https://www.cdfa.ca.gov/invasives/

California Invasive Plants Council (Cal IPC) invasive plant species that impact natural areas https://www.cal-ipc.org/plants/      These plants damage wildlife habitat, agricultural production and water resources.

2024 California Invasive Species Action Week Lunchtime Talks https://ucanr.edu/sites/invasivelunch/2024/

National Invasive Species Information Center US Department of Agriculture https://www.invasivespeciesinfo.gov/

Invasive Plants Pestnote https://ipm.ucanr.edu/PMG/PESTNOTES/pn74139.html

UC Riverside Center for Invasive Species Research  https://cisr.ucr.edu/invasive-species
https://cisr.ucr.edu/resources/invasive-species-faqs#how-can-invasive-species-be-ma

What are Exotic and Invasive Pests
https://ipm.ucanr.edu/invasive-and-exotic-pests/What-are-exotic-and-invasive-pests/

Have a gardening question? We'll help. You can reach us by:

• Emailing acmg@ucanr.edu. Please include a photo of the problem, if you can, plus your name, phone number, city and a description of the problem.
• Using our online form.
• By phone, during our office hours, 10 am to noon Wednesday and 11 am to 1 pm Thursday: 510-670-5645. At other times, please leave a message and we'll return your call during our office hours.
• In person at our Hayward office, during our office hours, only by appointment.