- Author: Help Desk Team
Perhaps you've seen them. You're digging into the soil to plant something and as you dig you run across a few earthworms. Most of us have heard from childhood that worms are good for the soil. You may also be aware of vermiculture, or worm composting, using worms to help turn organic waste into nutrient rich compost for the soil. When you see earthworms in your garden, what does their presence suggest about the soil health? Should you add more?
Earthworms and Wigglers
The earthworms you typically see in your garden are considered "migratory" which means they will travel to find the habitat best suited to their success. They tend to cluster in the top 6 to 8 inches of soil around the roots of plants where they feed on decaying material and the fungi and other organisms that live there. As they travel through the soil, they drag leaves and other litter down into their burrows where soil microorganisms also begin digesting the material. These worms can tolerate colder temperatures through the winter months when they burrow deeper into the soil.
Earthworms need a light airy soil and rely on decaying organic material for nourishment. Introducing these earthworms to an inhospitable environment such as heavy clay, or compacted and/or dry soil, will result in them either leaving or dying. Where they flourish, however, they are important in mixing the dead surface litter with the main body of the soil. If you regularly add compost and a layer of mulch to your garden to improve the soil you may find the worms 'magically' appear, attracted to the habitat you are creating. In turn their constant burrowing and feeding activities help mix and distribute organic matter throughout the soil, improve soil aeration and water penetration, promoting a healthier root environment for your plants. Their excrement, known as castings, is richer in nitrogen, potassium carbon, sulfur, and other minerals than the rest of the soil, and acts as a natural fertilizer.
There is a second type of worm which lives close to the soil surface in areas of abundant organic material. These worms, including the popular species red wigglers, reproduce rapidly and thrive in warm, crowded conditions. They are less likely to survive in your garden environment, particularly during cold weather. Instead, these worms are ideally suited to worm bins, and you will usually find them for sale for use in vermiculture. In a bin they can rapidly break down food scraps and other organic waste materials, and their castings also act as a natural fertilizer when collected and added to garden soils. Think of these worms as composting specialists.
A Note of Caution
There is a type of worm known as a jumping worm, an invasive species capable of harming native forests which has been seen in California and many other states. It is recognizable by a milky-white band wrapping all around its body near the head. When disturbed, jumping worms have been known to throw themselves into the air and thrash around. It is very difficult to eliminate these worms once established, so make sure to check new mulch, compost, and potting soil for the worms, as well as soil in nursery pots. Because they live close to the surface their castings are often visible as a coffee-ground-like substance on the soil. Don't use these worms for fishing, vermiculture, or gardening. You can learn more about jumping worms at https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=56929.
The Bottom Line
Should you add worms to your garden soil? Ultimately, it's a chicken and egg situation. Do earthworms create healthy soil or are they attracted to healthy soil? Few valid studies have been done to link the presence of earthworms with improved plant growth. However, both plants and earthworms need temperatures between 60°F and 100°F, water (but not too much or too little), oxygen, and a soil that isn't too acidic, basic, or salty. It's clear the conditions that are good for plants are also good for earthworms, and improving your soil by regularly adding compost and mulch ends up supporting a thriving community of both healthy plants and earthworms.
Help Desk of the UC Master Gardeners of Contra Costa County (RDH)
- Author: Kathy Keatley Garvey
Fact: At least 80 percent of those attending the Bohart Museum of Entomology's open house on entomophagy ate one or more insects--a cricket, an earthworm or a mealworm. The diners ranged in age from a 9-month-old girl to senior citizens.
Some came back for more--especially the mealworms and earthworms, said Bohart associate Emma Cluff. The crickets? Not so much.
A two-year-old from Dixon happily munched everything given to him. "He'll eat anything," his mother said.
Various companies, including Hotlix, Exo and Chirps Chips, provided the samples.
Besides eating insects, visitors asked questions about entomophagy and handled insects from the petting zoo, which includes Madagascar hissing cockroaches, walking sticks or stick insects, and tarantulas.
They also made buttons proclaiming "I Ate a Bug at the Bohart."
A display, titled "Bug Buffet," drew widespread interest: "Have you ever eaten ant pancakes or scorpion scaloppini? Well, eating bugs (entomophagy) is a lot more common than you might think. All round the world, people eat delicious and nutritious insect delicacies."
The dishes mentioned on the display:
- Locust Biscuits, featuring the brown locust, Locustana pardalina
- Mexican Caviar, starring the giant water bug, Abedus herberti
- Termite a la Carte, featuring termites, order Isoptera
- Maguey Worm Tacos, with Maguey worms, family Megathymidae
- Raw Cossid Moths, starring the larvae of the cossid moth, Xyleutes leucomochia
- Fried Pupae, presenting the pupae of the silkworm moth, Bombix mori
The next Bohart Museum open house, themed Parasitoid Palooza!, is on Saturday, Oct. 19 from 1 to 4 p.m. It is free and family friendly. The museum is located in Room 1124 of the Academic Surge Building on Crocker Drive.
"An insect parasitoid is a species whose immatures live off of an insect host, often eating it from the inside out," said Tabatha Yang, education and outreach coordinator of the Bohart Museum. "It is part of their life cycle and the host generally dies."
The late UC Davis entomologist Richard M. Bohart (1913-2007), founder of the Bohart Museum, researched Strepsiptera, or twisted-wing parasites, for his doctorate in 1938. Both the Bohart Museum and an entire family of Strepsiptera, the Bohartillidae, are named in his honor.
The Bohart Museum, directed by Lynn Kimsey, UC Davis professor of entomology, houses a global collection of nearly eight million specimens. It is home to the seventh largest insect collection in North America, and the California Insect Survey, a storehouse of the insect biodiversity. It also maintains a year-around gift shop, which is stocked with T-shirts, sweatshirts, books, jewelry, posters, insect-collecting equipment and insect-themed candy.
The insect museum is open to the public Mondays through Thursdays from 9 a.m. to noon and 1 to 5 p.m., except on holidays. More information on the Bohart Museum is available on the website at http://bohart.ucdavis.edu or by contacting (530) 752-0493 or bmuseum@ucdavis.edu. (See list of open houses for the 2019-2020 academic year.)
Penny Pawl, U. C. Master Gardener of Napa County
Worms are not native to North America. About 20,000 years ago, our continent experienced an Ice Age, along with Europe and Asia. The phenomenon decimated the worm population, with the only survivors in parts of Turkey and the Mediterranean.
Over time, as Eurasians and Europeans began migrating to new lands, they brought plants for their new homes with them. Worms and other critters hitched a ride. On the East Coast of the U.S., these worms have changed the ecosystem because they eat the fallen leaves that trees also depend on for nutrition. This phenomenon is changing East Coast woodlands.
As the immigrant settlers moved across the country, so did their worms. In the Western U.S., worms have benefited the land and consequently the crops that people grow.
If you dig in damp soil, you will probably run across at least one worm. These earthworms (Lumbricus terrestris) live in the first 12 inches of soil. Their digestive systems turn soil into ever finer soil, and their castings improve the health of the soil. Worms also turn the soil, creating tunnels for water and roots. They won't thrive in compacted soil.
Night crawlers (Eisenia hortensis) also live in the soil. However, when the air is damp, they come to the surface and feed on plants there. They are much bigger than red wigglers. Once I put two night crawlers in a worm compost bin. When I cleaned the bin the following year, there were still just two night crawlers in the bottom of the bin. These worms had no interest in composting. However, some night crawlers from Europe and Africa will apparently do this work.
Red wigglers (Eisenia fetida, also known as fishing worms or manure worms), are the kings of composting. They are the worms you find under a stone, pot or pile of leaves. They only eat decaying matter.
Once I put a layer of maple leaves in one of my bins. I seem to have raked up some maple seeds, too, because a week later I had a crop of baby maples in my compost. The worms ate the leaves but not the seeds, which were still fresh enough to sprout.
Red wigglers eat or chew 90 percent of what you give them and that includes newsprint, plain cardboard, egg shells, daffodil leaves, spent flowers, vegetable leftovers, coffee grounds and animal fur. From these materials they produce compost, a mild fertilizer that you had a hand in.
Spread your worm compost over a garden bed, water it in, and the nutrients return to the soil. A lot of gardeners also put a little worm compost in the planting holes for their vegetables for an extra boost. I feed my potted plants with a handful of worm compost.
African red wigglers (Eudrilus eugeniae) grow much longer than our red wigglers and eat more. The two types can survive side by side because they are not necessarily interested in the same decaying material. The African worms need higher temperatures, but I have corresponded with someone in Michigan who is successful raising them in his garage.
Other critters will move into your bins, too. Sow bugs or pill bugs will be the first to arrive, and their manure is just as good as worm castings. My compost-bin residents have included small toads, earwigs, slugs, snails, an occasional small snake (they like worms), a few lizards, ants and various flies. Most of these creatures coexist but I do get rid of the fruit flies.
This year I am experimenting with putting compost bins in my raised beds, a technique common to African keyhole gardens. I put a compost bin in the middle of each bed so the worms can travel back and forth and hopefully fertilize the bed they are in. Only time will tell whether this experiment is successful, but I will report back.
Workshop: U. C. Master Gardeners of Napa County will host a workshop on “Rose Care” on Saturday, June 2, from 10 a.m. to noon, at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Roses will grow without any care. But they will thrive with a little TLC! Master Gardener rose experts will answer your questions regarding rose care at this popular forum. By June, the first spring blooms have faded, and many plants are beginning to show stress. Look for black spot, rust, mildew and aphids. Bring samples of what's plaguing your roses. Online registration (credit card only); Mail-in/Walk-in registration (check only or drop off cash payment)
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
By David Layland, U. C. Master Gardener of Napa County
Climate change, also called global warming, has been in the news lately because of the devastating wildfires in Northern and Southern California. Climate change refers to the rise in average surface temperatures and is due primarily to the use of fossil fuels which releases carbon dioxide and other greenhouse gases into the air.
The gases trap heat within the atmosphere, which can have a range of effects on the environment including rising sea levels, severe weather events, and droughts that render landscapes more susceptible to wildfires.
There are two ways to mitigate the environmental damage done by fossil fuels. The most common way is to reduce the use of fossil fuels—by driving a hybrid or electric car, for example, or using solar or wind power. The second way, carbon sequestration, involves pulling carbon out of the air and storing it in the ground.
I don't drive a hybrid or electric car but I do have solar power. It provides 90 percent of my electricity at home so I've done something toward lowering emissions.
Carbon sequestration is new to me. In researching what I could do to help pull carbon out of the air, I discovered that I'm already using several carbon-sequestration practices in my garden. To some extent, these practices are what organic gardeners have been doing for a long time.
Make compost: One of the primary differences between organic and conventional gardening can be boiled down to a simple change in perspective: Instead of worrying about feeding the plants, we should worry first about feeding the soil. Take care of the soil and the plants will take care of themselves.
By composting all of our food scraps and garden waste, we aren't just providing valuable nutrients for plants. We are providing food for a huge ecosystem of bacteria, fungi and insects, all of which help to absorb carbon from the environment and keep it locked up in the soil. You can add cardboard and other paper-based waste to your compost, too. High-fiber composting works, and it's another way to lock up some CO2.
Don't dig: Many old-school gardeners may scoff at the idea of no-dig gardening, but there are good reasons to abandon the rototiller and dig only when necessary. No-dig gardening could have a significant impact on preserving soil carbon.
By slowing down the rate of decomposition in the soil, you help increase soil carbon and save yourself some labor. More than 15 years ago I purchased a rototiller because I thought I “needed” one for my garden and vineyard. I used it for a few years, until I realized I didn't need it. It sat under a tarp for a few more years until I found a new home for it.
That was an expensive lesson. Not using a gas-powered rototiller also means you are not using fossil fuels and are not spewing pollutants into the atmosphere. And you're not killing the hard-working earthworms that are improving your soil health.
When you refrain from tilling, you avoid exposing the soil to excess oxygen and sunlight. You can achieve the same thing by mulching, but an even better way is to plant cover crops, or so-called green manures, which can later be hoed in or mowed down. Doing so will add carbon to the soil while helping the root system keep soil in place. Cover crops also provide a habitat for soil life when you don't have edible crops.
Lose the lawn: This recommendation was easy for me. Before my wife and I moved to Napa, we had a lawn that was more than an acre and, of course, we had a riding lawnmower. After four years of mowing this lawn I never wanted to have another one.
The standard lawn requires a considerable amount of costly maintenance, water and chemicals if you want that green carpet to look perfect. There are many environmentally-friendly alternatives to a lawn. In Napa, I opted for decomposed granite. There's no maintenance and the permeable surface allows water to reach the soil. I added a few drought-tolerant plants for color and trees to shade the house. And I'm saving fossil fuels by not using a gas-powered lawnmower.
Grow lots of stuff (except a lawn): To store the maximum carbon, always keep the soil surface covered with growing things such as trees, turf, vegetables, flowers and cover crops. The more variety, the better. Grow plants with deep, extensive root systems and coarse, woody roots; shallow, fine roots decompose too easily. If I had it to do over again, I might not use as much decomposed granite as I did. At the time, I was focused on lawn alternatives, not on carbon sequestration.
So there you have some tools for carbon sequestration at home. Now go out there and do your part to fight climate change.
Workshop: U. C. Master Gardeners of Napa County will host a workshop on “Rose Pruning” on Saturday, January 13, from 10 a.m. to noon, at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Why do we prune roses? Is winter the only time to do it? What will happen if we don't? Should hybrid teas be pruned differently from floribundas? Join the Master Gardener Rose Team at this popular forum where resident experts will answer your questions about basic rose pruning fundamentals with research-based information. Topics include rose types, how and when to prune, what tools to use and how to care for them, safety and sanitation. No doubt each Master Gardener will have some suggestions for new plantings, too. Online registration (credit card only);Mail-in/Walk-in registration(check only or drop off cash payment).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
- Author: Ben Faber
There are 4,000 species of earthworms grouped into five families and distributed all over the world. Some grow uo to 3 feet long, while others are only a few tenths of inches. We call them nightcrawlers, field worms, manure worms, red worms and some people call them little diggers.
In California, we have some native species of earthworms, but in many cases non-native introduced species have come to dominate. The predominant native species belong to the Argilophilus and Diplocardia while many of the non-native are of European in origin in the Lumbricidae family. Many of these non-natives were probably introduced by settlers bringing plants from home, which had soil containing the worms. A survey of California earthworms by the US Forest Service can be found at:
https://www.fs.fed.us/psw/publications/documents/psw_gtr142/psw_gtr142.pdf
This is a wonderful description of earthworm biology and their occurrence in the landscape.
When digging in citrus orchards, it is common to find earthworms in the wetted mulch under tree canopies. Many of our citrus orchards were initially established by “balled and burlap” nursery trees that brought worms along with the soil. In the case of many avocado orchards, on the other hand, it can be rare to find earthworms in orchards. Most avocado orchards have been established since the 1970s when potting mixes and plastic liners were the standard practice and worms were not part of the planting media. Even though there is a thick leaf mulch in avocado orchards, the worms have not been introduced, and it is rare to find them.
Numerous investigators have pointed out the beneficial effects of earthworms on soil properties. One of the first of these observers was Charles Darwin who published Earthworms and Vegetable Mould in 1881. He remarked on the great quantity of soil the worms can move in a year. He estimated that the earthworms in some of his pastures could form a new layer of soil 7 inches thick in thirty years, or that they brought up about 20 tons of soil per acre, enough to form a layer 0.2-inch-deep each year.
Earthworms, where they flourish, are important agents in mixing the dead surface litter with the main body of the soil. They drag the leaves and other litter down into their burrows where soil microorganisms also begin digesting the material. Some earthworms can burrow as deeply as 5 to 6 feet, but most concentrate in the top 6 to 8 inches of soil.
The worm subsists on organic matter such as leaves and dead roots near the soil surface. The earthworm ingests soil particles along with the organic matter and grinds up the organic matter in a gizzard just as a chicken does. This is excreted in what we call worm casts. The castings differ chemically from the rest of the soil, as they are richer in nitrogen, potassium and other mineral constituents.
Castings are a natural by-product of worms. When added to normal soils in gardens or lawns, they provide the same kinds of benefits as other bulky organic fertilizers. Castings today are not commonly used as fertilizer by commercial plant growers because of their cost relative to other fertilizers. However, castings are used by some organic growers and are sold commercially as a soil amendment or planting medium for ornamental plants grown in pots.
The physical soil churning process also has several important effects:
-Organic residues are more rapidly degraded with the release of elements such as nitrogen, sulfur and other nutrients.
-Some of the inorganic soil minerals tend to be solubilized by the digestive process.
-Extensive burrowing improves soil aeration.
-Burrowing can improve water penetration into soils
-The earthworm carries surface nutrients from the soil surface and imports them into the root zone of the plant.
Although earthworms are considered beneficial to soil productivity, few valid studies have been made to determine whether their presence will significantly improve plant growth. This may seem odd since many of us have learned from childhood that worms are good. It is something like the chicken and the egg analogy. The conditions that are conducive to earthworms are also ideal for plants. Both plants and worms need temperatures between 60 and 100 degrees F for good growth; both need water, but not too much or little; they both require oxygen for respiration; and they do not like soils that are too acid or basic or too salty. By correcting soil conditions that are unfavorable for one will also improve the outlook for the other. The earthworm is a natural component of the soil population. If the soil is properly managed this natural population will thrive. In this sense, the presence or absence or earthworms can be an indicator of the "fertility" of one's soil.