Is there an area in your garden where you are battling noxious weeds or other invasive plants? If so, soil solarization is a solution that avoids the use of herbicides and saves you from the on-going work of pulling up the invaders. Our hot summer months are the ideal time to employ this method.
Solarization most effectively controls soil-borne fungal and bacterial plant pathogens such as those causing Phytophthora root rot, Southern blight, Verticillium wilt, Fusarium wilt, damping off, crown gall, tomato canker and potato scab.
Nematodes can be controlled but not completely eliminated by solarization, because they are mobile and can move through the soil. Control is most effective in the top 12 inches of soil.
While solarization kills many soil pests, beneficial soil organisms either survive or recolonize the soil rather quickly. Earthworms can retreat to lower depths. Beneficial fungi such as mycorrhizal fungi and bacteria that parasitize plant pathogens quickly reestablish themselves.
Solarization is most effective when days are long, temperatures are hot, skies are clear, and winds are mild. June to August is therefore the most effective time in the Central Valley. Prepare the soil by removing weeds, rocks or other debris. Break up dirt clods and create a smooth soil surface.
Use clear plastic to snugly cover the smooth soil surface. Lay the plastic as close as possible to the soil surface so there are few air pockets. Thin clear plastic (1 millimeter) provides the greatest heating potential but is more susceptible to tearing. Slightly heavier plastic (1.5 to 4 millimeters) may be best. The type of drop cloths used in painting work well. The plastic sheeting should be slightly bigger than the area to be solarized. Dig a trench around the area. Cover one edge of the plastic with soil to hold it down. Pull the plastic tight across the soil and bury the opposite edge. Do the same with all sides. Keep the plastic as close to the soil surface as possible.
The UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, call the Hotline at (530) 538-7201 or email mgbutte@ucanr.edu.
- Author: Laura Lukes
If you seek a peaceful place to explore nature and local history on foot or by bicycle, it may be time to explore Verbena Fields. This 20-acre site was historically a floodplain for Lindo Channel and later became used as a gravel mine for road construction.
The area was restored in partnership with state and local agencies, including the California Water Resources Board (a major funder), the CSU, Chico Research Foundation, Big Chico Creek Watershed Alliance, Streaminders, and the Mechoopda tribe. The restoration plan included input from neighbors, along with experts in wetland restoration, urban runoff mitigation, native plants, and local fauna. Together, these entities transformed a pile of rocks, broken asphalt, and noxious weeds into a natural refuge for humans, animals, and plants.
A wide, level path of crushed gravel (handicap accessible and suitable for small children and strollers) meanders along the perimeter of Verbena Fields. A second path bisects the site approximately at its midsection. We enter at the southwest corner, where Verbena Lane and East First Avenue intersect. Signage lets you know that your dog is welcome, on a leash, and at this corner there is a drinking fountain and a dog bag dispenser. To the left, a level strip of small trees, shrubs, and wildflowers borders the backyard fences that make up the western boundary of the site. To the right, desire lines (informal paths) lead from level ground to the Mechoopda Gathering Circle, a lowland area that features a beautiful tile mosaic depicting aspects of tribal life.
To the right is the open grassy area that comprises the bulk of the site and surrounds the wetland expansion portion of the project. The bisecting trail runs through the lupine and poppy (and also star thistle) that grow among the grasses. This middle trail affords access to a heavily shaded grove in which someone has fashioned a 10 to 12-foot- tall teepee from lumber scraps. An old rug has been placed inside, and it looks like a peaceful place to meditate, or the perfect place to play a game of fort.
Springtime at Verbena Fields is particularly beautiful: grasses are green and supple, redbuds, poppies, and lupines combine to make a palette of bright color, and fresh leaves bud from the limbs of the deciduous trees. Summer is dryer and crisper, but the shady groves of large trees and the low-lying cool spots offer respite from the heat. Fall brings the changing of colors when the grasses mellow to shades of heather, and in winter (if we are lucky with the rains) one can appreciate the value of the bioswales and wetlands features, as well as the view of the foothills to the east.
Whatever the season, Verbena Fields is a delightful place to visit. Just follow East First Avenue eastward, away from the busy bustle of traffic, to find it.
Most gardeners are aware of plant diseases that can wreak havoc in their gardens. If you grow fruit trees, you may be confronted with curled, reddened peach leaves (peach leaf curl fungus). If you grow apples or pears, your trees may sometimes look like they were scorched with a blow torch (fire blight bacterium). But did you know that viruses can also lurk in the leaves, stems, and fruit of your garden vegetables and flowers? A virus infection can reduce a plant's growth, lower its yield, and/or result in inferior fruit, vegetables, or flowers.
Viruses attach to cells, penetrate, uncoat, replicate, assemble, and then are released. The time between initial introduction and systemic plant infection varies from a few days to a few weeks. Transmission to other plants completes a virus's life cycle.
History
The first plant virus to be discovered was found on the leaves of tobacco plants in the late 19th century. Researchers found that sap from infected tobacco leaves caused green and yellow mottling (“mosaic”) symptoms in healthy plants. Unlike bacteria, this virus could not be filtered out, but boiling the sap destroyed the infectiousness. Tobacco Mosaic Virus (TMV), the first plant virus discovered, remains one of the most common plant viruses. It attacks not just tobacco but also other members of the nightshade family (Solanaceae), including eggplant, cucumber, pepper, potato, tomato, petunia, snapdragon, delphinium, and marigold.
Virus Transmission
Transfer of virus-infested sap may occur during agricultural practices (through damage caused by tools or hands) or naturally (by an animal feeding on the plant). Plant viruses can also be transmitted by insects, nematodes, fungi, and through pollen, seed, or vegetative propagation from infected parent plants.
There are many, many plant viruses that collectively have the potential to infect virtually all species of plants. Fortunately, host ranges of individual viruses vary from very narrow to very broad. Plants can prevent viral infection through either passive or active defenses. In passive defenses, some plants simply don't produce one or more of the factors required for a particular virus to reproduce and spread within that species. Active defenses detect and destroy or wall off virus-infected cells by the action of resistant genes in the plant.
Virus Symptoms
Viruses typically spread throughout the whole plant and cause a systemic infection. A plant's response to infection can range from completely symptomless to severe disease and plant death, depending on the host and the particular virus.
Typical leaf symptoms of a plant virus include mosaic patterns, chlorotic (yellow) or necrotic (brown) lesions, yellowing, stripes or streaks, vein clearing (becoming translucent), vein banding (where bands of a lighter or darker color occur alongside veins), and leaf rolling and curling. Flower symptoms include deformation and changes in the color and pattern of the flowers. Fruit and vegetable symptoms may include mosaic patterns, stunting, discoloration or malformation, and chlorotic ringspots. Stems may develop stem pitting and grooving or tumors in response to virus infection.
Disease Management
Understanding a virus disease is the first step. Consult the UC IPM website to help identify virus disease possibilities that might infect the plant species of concern. There is no cure for a virus disease once a plant is infected. Prevention or reducing spread between plants is the only possibility. Some viruses are spread by aphids and other insects that suck plant juices so controlling them on vegetables can be helpful.
Herbaceous ornamentals and certain vegetables are generally more susceptible to serious injury or death from viruses, especially when plants are young. Prevention includes using certified virus-free seed or plant material and elimination of virus reservoirs in surrounding vegetation. Grow virus resistant cultivars when available. Provide proper cultural care to improve plant vigor. Management depends on how a virus enters the plant, how it is transmitted between plants, and where it survives when susceptible vegetables are not present. Dig out and destroy virus-infected plants.
Tobacco mosaic virus (TMV) is also known as tomato mosaic virus. It commonly appears at this time of year. TMV infects a plant by entering a break in the cell walls caused by insects or other physical damage. Leaves infected with this virus become mottled with yellow and green spots. The dark green spots often appear thicker and somewhat raised, giving the leaves a blister-like appearance. Mottled areas may turn brown and wither. Plants infected with TMV may be stunted and produce very little fruit.
To manage TMV, remove and destroy any symptomatic plants. Avoid use of tobacco around tomato plants. Use only certified virus-free seed. Sanitation is the single most recommended practice to control TMV, because transmission of the virus from plant to plant usually occurs from contaminated tools or hands. The most common sources of infection are the debris of infected plants that remains in the soil. After removing diseased plants, wash your hands and decontaminate tools. Surface sterilize seeds with bleach before planting. There are no chemical sprays that will prevent, control or eradicate viruses.
Viruses rarely kill woody plants but may alter their appearance with line patterns or ring spots on their leaves. When available, planting certified virus-free stock is the best approach. Rose mosaic virus, is a common example that often has clear visual symptoms in the leaves, especially in cool spring weather. Controlling insects is not an effective method of preventing virus infection in woody ornamentals since low densities of pests can spread viruses throughout the life of perennial shrubs and trees. Virus infected ornamentals should be removed if severe stunting compromises the value of the plant in the landscape. Locally, many very productive almond orchards continue to be hosts of a mild plant virus. There is some debate in the commercial nursery industry as to whether or not this needs to be addressed with certified virus clean stock when trees are propagated for new orchards.
Several other viruses that affect garden plants and vegetables will be discussed in the next Real Dirt column.
The UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, call the Hotline at (530) 538-7201 or email mgbutte@ucanr.edu.
Record numbers of people are gardening this spring and victory gardens are rapidly sprouting across the nation. Now is a better time than ever to learn how to save seeds.
Some vegetables, like beans and peas, are self-pollinating. These are less likely to cross with other related varieties through insect pollination. Self-pollinating varieties are excellent choices for the beginning seed saver, as some pods can simply be left on the vine to dry out. Once completely dried, remove seeds from pods, place them in envelopes labeled with the variety and date and store them in an airtight container in a dry dark place. A mason jar placed in the refrigerator or freezer makes a good receptacle for seed packets. Properly stored bean and pea seeds should remain viable for three years.
Peppers cross easily due to pollination. You may notice your sweet bell peppers suddenly take on a spicy hot pepper quality if you don't separate pepper varieties by at least 100 feet or plant barrier crops in between varieties. But pepper seeds are some of the easiest to save; just remove seeds from the fruit and dry them for two to three days on a plate or paper towel. Properly stored pepper seeds remain viable for up to two years.
Some vegetables require much more care to ensure that seeds do not carry mixed or unexpected character traits. While corn is an American staple in the garden and whole cobs are easily dried, wind pollination leads to easy crossing between different varieties. If you want to save corn seed, grow only one variety in a large patch (or in patches of different varieties separated by 1,000 feet, if you have that much space). Members of the squash family within the same species readily cross and must be separated by a half mile or hand-pollinated to ensure a pure strain. Similarly, cole crops are all varieties of a single species, Brassica oleracea. Cauliflower, broccoli, Brussels sprouts, kale, cabbage, turnips, collard and bok choy will all cross with one another; therefore, growing only one variety at a time is recommended if you plan to save the seed.
For more information on saving seeds of all types, consult The Complete Guide to Saving Seeds by R. E. Gough and C. Moore-Gough, Seedsavers Exchange at www.seedsavers.org, your local seed lending library, or Beginner's Guide to Seed Saving” by Paul McCollum, UC Master Gardener of Monterey Bay.
- Author: Cheryl Cozad
In the wild areas on our planet, trees, bushes, and grasses grow on ground that has continual additions of new layers of dead and dying plant matter. Leaves fall from trees and shrubs, grasses dry in the summer: these materials cover the soil and gradually decompose. No Till gardening takes its cue from this natural process. There's no double-digging. No bi-annual rototilling. No weed pulling.
Soil is inhabited by billions of microscopic organisms. It is this abundant life, attracted to the sugars put out by plant roots, that creates a mutually beneficial feeding relationship with plants. Breaking up the soil by tilling, digging, or weeding disrupts these vital organisms.
No Till aids the soil's ability to retain water. The roots of previous weeds and other pre-existing plants create pathways for water to penetrate and be stored in the soil.
When you avoid tilling you'll have fewer weeds in your garden, since tilling brings weed seeds to the surface where light signals them to grow.
A No Till garden requires less work on the part of the gardener. Ultimately, a No Till bed will need less weeding, less watering, and less digging.
There is no need to wait before planting in a No Till garden – you just plant on top of the decomposing plant life.
There are several different approaches to creating a No Till garden. The simplest method is described here.
Materials you will need:
- Cardboard (with tape & labels removed) or newspapers (newsprint only – no colored ads or glossy pages).
- Compost, well-aged manure, worm compost, or organic soil mix. Organic blends are a little more expensive but they will do a better job of supporting the growth of your subterranean microbes, which help your plants get the nutrients they need for optimal growth and resistance to pests and diseases.
- Plants and seeds.
- Mulch (wood chips, straw, grass clippings, or pine needles).
- Select a sunny site. Think small. Two 5 x 10 - foot beds can grow a lot of produce. Even No Till gardening can get overwhelming if you take on too much.
- Cut existing vegetation to the ground and water the area well. Avoid burying large clumps or a thick layer of fresh green vegetation under a compost layer. Anaerobic decomposition can be detrimental to root growth.
- Apply a 4-to-6- inch layer of a well-composted mix. Well-aged horse manure (often available free from stables), plus worm compost makes a terrific mix. The City of Chico Compost Facility on Cohasset highway (currently closed due to COVID-19) sells finished compost that can be mixed with an organic soil mix or worm castings as another option.
- Cover the compost layer with overlapping pieces of cardboard, or 5 to 10 thicknesses of newspaper (overlapping them by one-third). Dousing the sheets of newspaper in a bucket of water will help stabilize them.
- For large deep-rooted plants (like tomatoes, peppers & eggplants) cut a circle in the cardboard or newspaper. Scoop out soil, add 2 to 3 shovelfuls of compost mix, and plant. For shallow-rooted vegetables or flowers, cut an X to open the cardboard or newspaper and plant smaller plants.
- Water well.
- Cover the bed with 4 to 6 inches of mulch. This will weigh down the cardboard or newspaper, prevent soil from drying out, and keep light from activating weed seeds. It also looks attractive.
- Install a drip or micro-sprinkler system or make a hand-watering schedule. Plan to water your No Till bed daily for the first week. Gradually taper off to every 3 to 5 days.
- Repeat! When a crop is finished, cut it to the ground, add compost, tuck in new plants, and mulch heavily.
Plants love the even moisture and lower soil temperatures created by No Till and mulch. Give it a try. Your microbes and your back will thank you.
For inspiration, browse the California State University, Chico Regenerative Agriculture website. For specific vegetable planting times, see our Planting Guides for the Chico Valley Area and for the Foothills.
The UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, call the Hotline at (530) 538-7201 or email mgbutte@ucanr.edu.