- Author: Help Desk Team
Note: This was originally published in the Contra Costa Times
Conquer weeds by understanding their life cycles
As a gardener in Contra Costa County, you know from observation that weeds have an immense capacity to produce seeds. In fact, the high reproductive output of weeds is astounding. Per plant, pigweed produces 117,400 seeds, mullein 223,200, lambsquarters 72,450, shepherd's purse 38,500, johnsongrass 80,000, curly dock 29,500, and wild mustard a mere 16,000 seeds.
Weed flowers can be small and inconspicuous, but, after flowering profusely over a period of several months, they produce a tremendous quantity of seeds. Black medic, kikuyugrass, and spotted catsear flower 5 to 7 months. Dandelions bloom 9 months out of the year and each flower produces thousands of wind-borne minutely barbed pappus-bearing seeds which can germinate year-round.
The sheer quantity of seeds ensures waves of seedlings. Yet, germination is discontinuous: it doesn't happen all at once. In gardens and in other disturbed areas, seeds are stored in the soil until shallow tillage brings them to the surface where conditions for germination are ideal.
Weed seeds persist in the soil below the germination zone and can be viable for a surprisingly long period of time. Mustard seeds thought to be 600 years old were excavated from a monastery garden in Denmark and 11 of them germinated. The longevity of field bindweed seeds is over 50 years. Lambsquarters seeds are viable for 20 to 50 years. Grass seeds tend to live an average of 3 to 10 years, whereas broadleaf weed seeds can be part of the soil seedbank for a much longer time
Life Cycle of Weeds:
Like other members of the plant kingdom, weeds are classified as annuals, biennials or perennials. The seeds of summer annuals germinate in the spring and mature plants generate seeds in summer and fall. Winter annuals sprout in the fall, live through the winter and produce seeds during the winter and spring. Biennial weeds spend their first year producing leaves before they flower and bear seed during their second and final year of life. Perennial weeds propagate by seeding but also vegetatively by means of creeping roots, rhizomes, taproots or bulbils. Weeds in their various stages of growth, flowering, seed production and dispersal are with us all year.
Weed Seed Dispersal:
Weed seed dispersal is varied and opportunistic. Though many mature weed seeds fall next to the parent plant, quantities of others are tumbled along or parachuted for miles by wind. Some burst out of capsules, landing 3 to 15 feet away. Others hitch a ride by attaching themselves to animal fur with burs or seed hooks. Many are digested by birds or livestock, transported by water or by the gardener's boots and tools. In their quest for territorial expansion, weeds use gardens as seed factory sites, as seed storage facilities and as launching pads for seed dispersal by gardeners.
Production of large quantities of seed, opportunistic seed dispersal, long- flowering periods, long seed viability, year-round seed production, and
discontinuous germination are successful strategies that weeds use to ensure their survival and expansion.
Managing Weed Seeds:
Weed seed management works best if you combine methods of control. Choose an irrigation system such as drip irrigation or microsprinklers so that only your plantings are watered. Be aware that cultivation brings weed seeds to the surface where they can germinate. Do not let weeds go to seed and replenish their weed seed reservoir in the soil. Reduce weed seed germination by eliminating their light source through use of a thick layer of mulch.
For More Information:
If you would like more information about identification of and controls for specific weeds, consult these University of California web sites:
https://wric.ucdavis.edu/
http://ipm.ucanr.edu/PMG/menu.weeds.html
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7441.html
Help Desk of the UC Master Gardeners of Contra Costa County (CG)
- Author: Help Desk Team
Note: This was originally published in the Contra Costa Times.
Q: I know that acorns are the seeds of oak trees, but how do I plant them?
A: Oaks are an important part of the California landscape. If you are lucky enough to have oak trees on your property, or access to others' oak trees, you can collect the acorns and plant them. There are some simple things you can do to ensure a good start for your oaks.
Selecting the Site:
First of all, only plant a given oak species in areas where it naturally occurs or has grown in the past, and only use acorns from oaks growing in the same general environment as the planting site. Even within a species, there are genetic adaptations to different soils and climates. Use acorns from trees that grow as close to the planting site as possible.
Collecting Acorns:
Collect acorns in the early fall, when they are just starting to turn from green to brown and the first ones fall to the ground. Acorns collected from trees are generally healthier and more likely to germinate than those that have fallen to the ground. Pick them from the tree, twist off the caps (they should come off easily) and immediately put the acorns in the refrigerator to slow their metabolic activity.
If you collect them from the ground, discard any that are broken, cracked, very small, or lightweight, and soak them for a day in water, discarding any that float. Then dry them off and put them in plastic bags in the refrigerator.
Storing Acorns:
Although they can be planted right away, acorns that have been stored in the refrigerator for one month have higher germination rates than those planted right after collecting. Check them for mold, and if any mold develops, rinse it off, dry the acorns, and put them back in the refrigerator in plastic bags. Leaving part of the bag open at the end helps to reduce mold growth. If you see white tips emerging from the pointed end of the acorns during storage, it's best to plant them right away. That's the start of the root system emerging, and it can turn dark and mushy if left in storage.
Planting Your Acorns:
The best time to plant the acorns is from November after the first rain to early March. However, earlier is better to give them more time to grow before hot weather arrives.
Plant them in full sun. Keep the eventual height and canopy size of the tree in mind when you choose a location. Loose, well- drained soil is best, and the area should be fairly free of weeds.
Plant the acorns one half to one inch below the soil surface. Dig a hole several inches deep then partially backfill it. Place the acorns on their sides in the holes and cover with soil. If they've already started to germinate, plant them root down, being careful not to break the root tip. If you have a lot of nearby pocket gopher or ground squirrel activity, you can give the acorns a better chance by planting them two inches deep, but don't go any deeper than that or the acorns will rot.
You can also start the acorns in containers and plant the seedlings later. For information about this method, see the UC web page, How to Grow California Oaks (https://oaks.cnr.berkeley.edu/how-to-grow-california-oaks/).
Caring for Your Trees:
Weeds, especially grasses, will out-compete oak seedlings for sun, water and nutrients, so keep a two-to-three-foot radius around each seedling clear of weeds. Remove weeds by hand or with a hoe. Mulch suppresses weed growth and helps conserve soil moisture. Bark chips, straw, compost, or paper can be used.
Oaks develop vigorous and large root systems—that's how they survive drought. If the rains are very light, one or two deep supplemental waterings in late winter and early spring can help the seedlings survive through their first summer.
Acorns and oak seedlings are an important food source for rabbits, insects, mice and other animals. A variety of protective devices can be used to prevent their damage.
With some encouragement and protection, your seedlings will be well on their way to becoming oak trees. You may not live to see them mature, but future generations will enjoy these magnificent trees.
Help Desk of the UC Master Gardeners of Contra Costa County (EM)
- Author: Help Desk Team
It's getting close to the end of our summer gardening season. Now is the time to start thinking about next summer's garden. Do you have annual flower or vegetable varieties that did really well in your garden, and you'd like to grow them again next year?
Saving seeds to plant for a new crop is an ancient but simple and enjoyable process. In fact, it was routinely practiced until the 19th century when seed companies started to multiply. Seed saving is especially useful if the seeds for the item you want are hard to find. Additionally, it enables you to replant varieties that are well-suited to your garden's particular conditions.
Saving seeds from your own garden will start with seeds from the healthiest plants and produce that have the characteristics you want. You might choose the flowers that last the longest, or a vegetable plant that is most productive. You should also choose seeds from plants identified as “open pollinated” or “heirloom”. Seeds from hybrid varieties may not grow into plants even remotely like the variety you are growing.
Some plants such as tomatoes and most beans self-pollinate so their seeds will grow true to the variety. Others are pollinated by insects (e.g., squash and cucumbers) or wind (e.g., corn). If the original seeds are from open pollinated wind- and insect-pollinated plants, saved seeds may give unexpected results if there are other varieties of that vegetable or flower growing nearby. Flowers with easy-to-save seeds include calendulas, columbines, foxgloves, nasturtiums, poppies, sunflowers and zinnias.
Let seeds mature on the plant before collecting. This usually means leaving them longer than you would for good eating quality and letting some seed heads dry on the plant rather than deadheading. Determining when to harvest for seed saving is generally based on whether the seed is classified as wet or dry. Tomatoes, peppers, eggplants, and squash are examples of wet seeds. Wet seeds should be collected when the vegetable is slightly overripe. Beans and peas are dry seed plants. They should be harvested after the pods are fully mature and dry, and the beans or peas inside are hard.
After harvesting, there are three steps: cleaning, drying, and storing.
To clean wet seeds, separate them from the fleshy vegetable, rinse until they are clean, and spread them out to dry thoroughly. Dry them on a screen or a pan as the dried seed can be difficult to separate from paper towel or newspaper.
Some wet seeds, such as tomatoes, need another step before rinsing and drying. This mimics a natural process that lets beneficial microorganisms develop to remove a gelatinous coating on the seeds and destroy seed-borne diseases. Soak the seeds in their own juice (add about half as much water) for several days until a white mold appears. Swirl them daily. The viable seeds will sink to the bottom. Drain off the mold and anything floating, rinse the seeds well, and proceed with drying.
Cleaning dry seeds is easier. Dry seeds and pods are produced by beans, peas, lettuce, chives, most crucifers, and most flowers. After the pods or seed heads are fully dry, remove the seeds from their surrounding pods and membranes, also known as ‘chaff'. One method to remove the chaff is to rub the seeds against something mildly abrasive, such as a screen. Then, put the seeds in a jar; pour the seeds into another jar outside in the wind, or in front of a fan, and let the air carry the chaff away.
Make sure seeds are completely dry before storing. Store dried seeds in an airtight container in a cool place to avoid exposure to moisture and heat. Mark the container with the name of the plant, the date, and any notes on color, location, or size.
For more information on saving seeds, see these links:
• Beginners guide to seed saving: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=11597
• Seed saving basics: https://mgsantaclara.ucanr.edu/garden-help/how-to/seed-saving/
• Saving seeds of popular plants: https://mgsantaclara.ucanr.edu/garden-help/how-to/seed-saving/saving-seeds-of-popular-plants/
• Video: https://www.youtube.com/watch?v=edUwq0wMztM&t
• Book: What We Sow by Jennifer Jewell
Help Desk of the UC Master Gardeners of Contra Costa County (SEH)
- Author: Help Desk Team
Spider mites are very common pests found on many of our landscape and vegetable garden plants. They are tiny and difficult to see but once you learn about them, you might start seeing evidence of infestation on a wide variety of plants.
Spider mites live in colonies, mostly on the back side of leaves. They are less than 1/20 of an inch long, have eight legs, and if you look carefully, you can see two red eyespots. When their population is high, you might see dense webbing covering the leaves, twigs, or fruit.
Spider mites use piercing mouthparts to suck cell contents from leaves. Damage appears first as a stippling of light dots on the top of the leaves. Evidence of their presence can be seen or felt on some leaves—fecal matter, cast off exoskeletons of young mites, dead mites, and fine webbing becomes more obvious with heavy infestations. With heavier infestations, leaves can turn yellow and fall off.
Spider mite activity is most severe and damaging during hot, dusty conditions, and when plants are water-stressed. June through October are prime months for these little pests. In Contra Costa's relatively mild climate, spider mites can feed and reproduce year-round on evergreen plants. On deciduous plants, they can spend the winter under rough bark or on the ground.
To control spider mites, make sure your plants are not drought stressed. Dusty conditions often encourage spider mite outbreaks. Regular, forceful spraying of your plants with water, especially the undersides of the leaves, will often reduce their numbers and the damage they do.
Spider mites have many natural enemies that help control them, including lacewings, predatory thrips, and predatory mites. Maintaining a diverse garden habitat can encourage these predatory mites and insects to stay in your garden, waiting to assist with pest control.
If more control is needed, consider using an insecticidal soap or an insecticidal oil such as Neem oil in your sprayer and make sure you spray enough to fully cover both tops and bottoms of leaves. You'll need to spray soap again two or three days later to cover any newly hatched spider mites, because soap doesn't have residual action.
If you choose to spray insecticidal soap or insecticidal oil, don't spray if temperatures are over 90 degrees F and make sure to follow the label instructions. Before spraying it on the whole plant, test it on a few leaves to make sure it doesn't damage them. Using broad spectrum insecticides is not recommended as these can kill the natural enemies of spider mites, which may result in an increase in the spider mite population
How to prevent spider mites
Scout plants for their presence anytime hot and dry conditions occur. If you catch spider mites early, you may be able to prevent a large infestation just by removing a part of a plant or a single plant. Watering down dusty walkways and misting plants when it's hot and dry can make it less attractive to spider mites. If a plant becomes too infested and treatments are not working, consider removing that plant to reduce the chance of the spider mites traveling to other nearby plants.
For more information on managing spider mites, see this Pest Note: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7405.html
Help Desk of the UC Master Gardeners of Contra Costa County (SEH)
- Author: Help Desk Team
This time of year, as the heat increases and things start to get dusty, you might see a number of webs on your plants. Uh oh. Are these webs a sign of spider mites?
Chances are the webs you see covering the ends of branches are actually created by spiders, a close relative to spider mites, and are nothing to worry about. Spiders are predators of insects, some of which are pests, and the webs are used for capturing prey. According to the UC Cooperative Extension, there are at least 54 families and over 1,000 species of spiders in California (https://ipm.ucanr.edu/natural-enemies/spiders/#gsc.tab=0).
Most spiders are beneficial to your garden. Think of them as a free pest control service and remember that among poisonous spiders only the widow spiders are commonly found in California, and these generally stay hidden in places like cellars or woodpiles. And even though the vast majority of spiders are harmless, that doesn't mean you want them surprising you in the garden! You can learn to recognize the many types of spiders hunting among your plants. Some of the more common web-spinning spiders you might see include:
• Dwarf Spiders: These tiny spiders hunt during the day and produce sheet-like or irregular crisscross webs on plant surfaces. You will find them in the plant canopy and in ground litter. They are common in fields and vegetable crops.
• Cobweb Spiders: Hang upside down in sticky, irregularly spun webs waiting for prey. Most are small and harmless, although widow spiders fall into this category.
• Funnel weavers include the Common House Spider: These spiders hang out in the garden, and on walls and ceilings in the house. They feed during the day and night, hiding and waiting for their prey near the ground in most types of vegetation. They spin funnel shaped webs, often with a flat extension covering the plant or soil. Their webs become conspicuous in morning light after collecting dew.
• Orb weavers or Garden Spiders: Often large and colorful, these spiders spin elaborate webs in concentric circles in the garden. They wait in their webs or nearby for prey to become entangled. Often, we can tell the species of the spider by the pattern woven into their web.
• Sac spiders: Typically nocturnal, Sac spiders live in silk tubes in places such as corners, beneath plants, or on bark, and stalk their prey at night. They occur both indoors and out.
Spiders that don't spin webs include the jumping spiders, lynx, crab and wolf spiders. Like their web-spinning cousins, these spiders are beneficial in your garden, preying on insects and other pests.
Are the webs damaging my plants?
In these photos you can see spider webs on a Daphne shrub, some succulents, and a Japanese Pieris. Notice there is no visible plant damage associated with the webs, although occasionally some dead leaves may get caught in a web, such as with the Japanese Pieris. A closer inspection shows the web hasn't caused the leaf damage — in this case it's sunburn from the recent heat wave.
Try to refrain from using insecticides as they aren't necessarily effective on the spiders, and you risk killing other beneficial insects. You can remove cobwebs from your plants by sweeping or hosing them away, or if inside, with a vacuum cleaner or mop. Instead, learn to recognize the spiders in your garden and you will come to appreciate the antics of the jumping spiders, or the beauty of a web with droplets of dew shining in the early morning.
• Quick Tips about spiders: https://ipm.ucanr.edu/QT/commongardenspiderscard.html
• Video to help you learn to identify spiders: https://www.youtube.com/watch?v=Bs-OUvY8L80.
• Identifying and managing spiders: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7442.html
Help Desk of the UC Master Gardeners of Contra Costa County (RDH)
