We have endured multiple years of drought, and are probably in store for more. For many of us, it makes sense to replace all or part of our lawn area with less water-intensive plantings.
Step One: observe and plan. What existing trees and plants do you want to keep or remove? What are the sun and shade patterns within your yard? What types of grass grow in your lawn? Do you want any additional amenities, such as paving or a shade structure? How will you irrigate your new plants?
Step Two: kill your lawn. Homeowners can use two eco-friendly methods to kill their lawns: Solarizing or Sheet Mulching. For detailed instructions on solarizing, see UC IPM Pestnote on solarization. For instructions on sheet mulching, see our Real Dirt blog post on Sheet Composting.
Sheet mulching kills weeds by starving them of light. It takes 6 to 10 months and can be started any time of the year as long as at least three months of growing season are included. Sheet mulching works in sun or shade, and is effective on all grasses, including Bermuda grass, and many annual and perennial weeds. It is left in place permanently; over time, the dead lawn, sheeting, and mulch will break down into soil-enriching compost. Sheet mulching should be placed before new plants are installed if being used alone to kill lawn or weeds. It can be placed after plants are installed if solarizing has been completed first. New hardscape and irrigation should be installed before commencing solarizing or sheet mulching.
Step Three: replant. Whichever method you choose to kill your lawn, time it so that you are ready to replant in the fall, winter, or early spring. The cool temperatures and moist soils of our wet season allow drought tolerant plants to develop the healthy roots they need to thrive with little water during the heat of summer. Taking time to thoroughly kill the grass and waiting until the climate conditions are suitable for new plants will ensure the long-term success of a lawn replacement project.
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, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
- Author: Margaret Gullette Lloyd
The days are long and the temperatures are high. This is a great time to solarize the soil in the Central Valley as a way to manage annual weeds and improve the growth of fall crops.
What is solarization? A non-chemical approach to weed control, soilborne pest management and soil enhancement using solar heating of plastic-covered moist soil. This method allows the sun's radiant energy to be trapped in the soil thereby heating the upper levels, killing and/or suppressing soil pests.
Watch video here: Clip of laying plastic with a tractor for soil solarization.
Why solarize?
- Kills or weakens many crop pests such as plant pathogenic bacteria and fungi, insects, nematodes and weeds within 2-12 inches +/- of the soil surface
- Soil physical and biological benefits
○ Increases levels of soluble, mineral nutrients available to the subsequent crop (nitrogen in the form of ammonium and nitrate, calcium, magnesium)
○ Generally less lethal to beneficial microbes than to plant pests
○ Increases breakdown of organic matter
○ Improves soil tilth
- Effects often last for multiple seasons, though best effects are directly after solarization
- Can work in combination with other pest management techniques such as steam, hot water, fumigants and pesticidal chemicals, biological controls, organic amendments (“biosolarization”), and host resistance
Watch video here: Paul Underhill discusses how has used soilsolarization
Solarization Factors:
Temperature: Solarization should be done in the warmest part of the summer. Usually this is between June and August in California. (See http://ucanr.edu/sites/solarization/california_air_temperature_maps/ for average temperatures for different months and locations in California.)
Timing: 4-6 weeks for maximum benefits (even 1-3 can provide some effects; time may be reduced with combinations such as biosolarization)
Soil preparation: Soil should be as smooth as possible to get maximum soil-plastic contact. This can be achieved by finishing with roller or bedshaper, or working the soil by hand and removing any large debris or clumps.
Plastic*: The most commonly used plastic is transparent polyethylene. Optimal thickness is 025-.03 mm unless solarization is being done in a particularly windy or animal-trafficked environment, in which case slightly thicker plastic should be used. Infrared-transmitting plastic can be purchased to facilitate a slightly higher temperature increase. Plastic with additives to decrease brittleness-causing sun damage can also be purchased.
Moisture: Soil moisture should be at 70% of field capacity in the upper layers of the soil and moist up to 24 inches deep to obtain maximum benefits. It should crumble easily when squeezed. When moistened prior to plastic, soil should be covered as soon as possible to avoid evaporation. When done after, water can be added via drip lines, furrows or hose pipe outlets under the plastic.
Beds: Plastic can be laid in strips over beds (min. 30” beds) or continuously for complete coverage. Strip coverage tends to be less effective than complete coverage because there is a cooling effect on the edge of the beds. For complete coverage, plastic can be installed by hiring a custom applicator, or can be laid in strips and joined by glue.
Bed specifications: For strip solarization, wider bed tops will accumulate more heat. It is best to solarize on strips with north-south orientation rather than east-west, to minimize shading. Beds with no slope or a slight south-facing slope will yield optimal results.
Plastic placement: Plastic can be lain by machinery or by hand. It is important that the edges of the plastic are buried.
Repair: If tearing occurs, plastic can be patched with patching tape.
Possible Disadvantages:
- Challenges associated with plastic disposal
- Perennial weeds, bulbous weeds, and seeds with a hard seed coat are harder to control
- Climate factors, such as fog and wind, may impede solarization
- May decrease root nodulating rhizobial bacteria in the soil
- May increase purple nutsedge under certain circumstances
Further information:
Check out videos, how-to and the science of solarization here.
* Plastic can be sourced locally from Irrigation Supply Co. in Woodland. The price is $137.14 for a 60” x 4000' x 0.001” roll. Plastic is usually in stock, though should be ordered several weeks to months in advance for large orders.
Short List of Pests Controlled by Soil Solarization (for a complete list, visit references) |
|||||
Plant Diseases |
Nematodes |
Weeds |
|||
Fusarium Wilt (tomato, cucumber, strawberry) Pythium, seedling disease Phytophthora root rot Rhizoctonia, seedling disease Verticillium Wilt |
Corky Root (tomato) Lettuce Drop White Rot (Garlic and onions) Southern blight Black root rot (many crops) Crown gall (many crops) Canker (tomato) Scab (potato) |
Ring Stem and bulb Potato cyst Northern root knot nematode Lesion nematode Citrus nematode Dagger nematode |
Velvet leaf Pigweed Fiddleneck Wild oat Black mustard Shepherd's purse Lambsquarter Miner's lettuce Field bindweed (seed only) Horseweed Large crabgrass |
Barnyardgrass Goosegrass Henbit Cheeseweed Branched broomrape Bermuda buttercup Annual bluegrass Purslane |
Common groundsel Prickly sida Black nightshade Hairy nightshade Sowthistle Common chickweed Horse purslane Common cocklebur |
Short List of Pests Unpredictably Controlled by Soil Solarization |
|||||
Diseases |
Nematodes |
Weeds |
|||
Charcoal Rot (many crops) Bacterial wilt |
Southern root knot nematode |
Field bindweed Bermudagrass Yellow nutsedge |
Purple nutsedge Lovegrass Bull mallow |
White sweet clover Johnsongrass |
References:
Elmore, C.L., Stapleton, J.J., Bell, C.E., & Devay, J.E. (1997). Soil Solarization: A Nonpesticidal Method for Controlling Diseases, Nematodes, and Weeds. (Publication No. 21377). Oakland: University of California Agricultural and Natural Resources.
Stapleton, J.J. (n.d.). Solarization for Vegetable Weed Control. California Weed Science Society. Retrieved from http://www.cwss.org/uploaded/media_pdf/59-67_2007.pdf
Yaduraju, N.T., & Mishra, J.S. (2004). Soil Solarization: An Eco-Friendly Approach for Weed Management. In Inderjit (Ed.), Weed Biology and Management. (1st ed., pp. 345-362). Dordrecht, Netherlands: Springer Science + Business Media.
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.
By Susanne von Rosenberg, UC Master Gardener of Napa County
Weeds can serve some useful purposes, but unless you're an unusual gardener, you probably still prefer to decide what gets to grow in your garden and what doesn't. The four basic weed control methods are prevention, removal, smothering and exhaustion. Most gardeners will need a combination of these methods to control their weeds.
Annual weeds (those that sprout from seed each year) are easier to control than perennial weeds (those that regrow each year from underground structures such as roots, tubers and underground stems). Perennial weeds can spread from their underground structures and by seed.
Prevention consists of all the activities that keep weeds from growing or spreading. The most important one by far is preventing weeds from setting seed. Some plants, such as wild oats, produce “only” about 250 seeds per plant. More ambitious weeds can produce over 200,000 seeds per plant.
It's also important to avoid promoting weed growth. Soil scientists estimate that there are 140 weed seeds per pound of surface soil in cropland (or 200 million per acre). Most weed seeds sprout from the top half-inch of soil. If you can avoid disturbing the soil, you can minimize the weed seeds you bring to the surface for germination.
Controlling drip irrigation is another weed prevention method. Only put water where you want plants to grow.
Mulch is effective in controlling annual weeds as long as it's thick enough. Mulches prevent light from reaching the weed seeds, so weeds can't grow. I prefer mulches from natural materials, such as wood chips and compost. Coarse mulches need to be three to six inches thick to keep out the light, and finer mulches such as sawdust and grass clippings need to be one to three inches thick.
Make sure that water can still reach your plants; mulches absorb some of the water. Certain quick-growing vegetable plants, such as squashes, beans and tomatoes, form a thick leaf cover that also helps to shade out weeds.
If you feel ambitious, you can kill many weed seeds through soil solarization. This process will take four to six during the hottest part of the year, so you will not be able to grow a summer garden in that area. To be effective, it needs to be done correctly. The UC Integrated Pest Management Program website has detailed information.
To avoid spreading weeds between different areas of your garden or between your garden and someone else's, clean your garden equipment, clothing and shoes. Finally, avoid importing seeds. While manure is great for your garden, make sure it's composted first. Horses and cattle can pass 20 percent of the viable seeds they eat. Composting can kill many of those seeds, but bird manure is usually a better choice.
As for removal, one effective approach is “water, wait, cultivate.” Ready your planting bed several weeks before you intend to plant, and then water it to encourage weed seeds to sprout. Hoe out the sprouts, keeping your hoe shallow to cut off the weeds just below the surface. Then repeat this process. This approach will remove about 95 percent of the weeds that would normally sprout. When you plant, disturb the soil as little as possible to avoid bringing new weed seeds to the surface. Keep hoeing or removing weeds by hand throughout the growing season. If you've applied mulch, it's usually easy to remove the relatively few weeds that sprout by hand.
Smothering weeds is simply another form of mulching known as sheet mulching. Cut back your weeds to six inches or less and cover the area with cardboard, overlapping the sheets by at least six inches. Apply mulch on top of the cardboard. The cardboard will break down in three to four months if you keep it moist, and it prevents annual weeds from returning.
Sheet mulching will also temporarily banish perennial weeds, but they may re-emerge after the cardboard has broken down. For me, sheet mulching is the fastest and easiest way to reclaim weedy areas.
To get rid of perennial weeds that are already established in your garden, you need to exhaust their food supply stored in their roots or other underground structures. Let them grow a bit, cut them back to below the ground surface, then let them grow a bit again. Don't let them grow a lot because that could allow them to store more food. This process may take several years to work. If you have widespread perennial weeds (for example, Bermuda grass), you can repeatedly mow them close to the ground.
You might have noticed that I did not mention herbicides. They are truly a last resort and are usually not needed in home gardens. If you are growing your ornamentals, food plants and turf correctly, they will outperform most weeds. If you do have to use herbicides, follow the label directions carefully and use the least amount possible. However you tackle your weeds, just remember: they may be tough, but you're a lot smarter.
UC IPM has more information about weeds for Napa county home gardeners. Start here:
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7441.html
The UC Master Gardeners of Napa County are volunteers who provide University of California research-based information on home gardening. To find out more about home gardening or upcoming programs, visit the Master Gardener website (napamg.ucanr.edu). Our office is temporarily closed but we are answering questions remotely and by email. Send your gardening questions to mastergardeners@countyofnapa.org or leave a phone message at 707-253-4143 and a Master Gardener will respond shortly.
- Author: Anne Schellman
- Author: Karey Windbiel-Rojas
Pests have popularity contests too. We recently looked at how many visits our popular Pest Notes publication series received in 2017.
If you aren't familiar, the UC IPM Pest Notes series are science-based publications written and reviewed by experts on specific pest or management topics for California. UC IPM has 169 Pest Notes with some being more popular than others.
Here are the 20 most visited titles in 2017:
1- Carpet Beetles
2- Peach Leaf Curl
Backyard peach and nectarine trees often suffer from peach leaf curl, a common fungal disease in California. The disease causes curling and deformation of peach and nectarine leaves and if left uncontrolled for multiple years, the tree may eventually die. Read more about it in the Pest Notes: Peach Leaf Curl.
3- Aphids
Warm weather means populations of aphids continue to live and breed, and you may be seeing these insects on your roses and other plants already this season. Learn about their fascinating life cycle and best management tactics at Pest Notes: Aphids.
4- Clothes Moths
The larvae of this moth attacks wool clothing, carpets, rugs, upholstered furniture, furs, and much more. If you think you might have this pest, consult the Pest Notes: Clothes Moths for help.
5- Scales
Many people overlook scales on their plants because they don't look like normal insects. Scales have strawlike mouthparts and suck juices from plants, sometimes leading to damage. Learn about the many different types of scales, host plants, and how to manage them at Pest Notes: Scales.
6- Thrips
7- Spider Mites
Spider mites thrive during dry, dusty conditions and usually escape detection until large populations build up and create copious webbing that covers plants. Luckily, there are natural enemies of spider mites that help keep their populations in check, including the western predatory mite. Learn management techniques at Pest Notes: Spider Mites.
8- Whiteflies
Whiteflies are small, flying insects that can attack a number of garden and landscape plants. They usually occur in groups on the undersides of plant leaves and excrete a sticky honeydew that may be covered with sooty mold. Find out more about this garden pest at Pest Notes: Whiteflies.
9- Fire Blight
In spring, some fruit tree shoots may appear burnt, a symptom of fire blight. This disease causes flowers, shoots, and young fruit to shrivel and turn black. Some trees are more susceptible to fire blight. Read about this disease in the Pest Notes: Fire Blight.
10- Fungus gnats
11- Leaffooted Bug
Leaffooted bugs are not new to California, but recently some areas have seen an increase in their presence and feeding damage. Learn more about this odd-looking bug and what it eats in Pest Notes: Leaffooted Bug.
12- Rats
Rats in your home and garden are destructive and can transmit disease. If you suspect the presence of rats, you'll first need to determine which of the two species (Norway rat or the roof rat) you have in order to effectively manage them. Find out by reading Pest Notes: Rats.
13- Ground Squirrel
14- Widow Spiders
Many people are afraid of black widow spiders and any spider that resembles them. Some spiders that look like black widows are actually harmless or less venomous relatives. Learn how to differentiate between them by reading the Pest Notes: Widow Spiders and Their Relatives.
15- Bed Bugs
Reports of bed bugs have been on the rise for the past few years. They are blood-sucking creatures that inspire revulsion in most people. If you travel, you'll want to know what bed bugs look like and how to avoid bringing them home with you. Read the Pest Notes: Bed Bugs and watch the related videos on this topic.
16- Bark Beetles
Bark beetles are small, about the size of a grain of rice, but in large numbers their larvae can do significant damage when they mine galleries just beneath the outer bark of trees. To learn more about bark beetles and their impact, visit the Pest Notes: Bark Beetles.
17- Pocket Gophers
You spot fresh mounds of soil in your garden or landscape. Could it be gophers? These small mammals can cause a lot of damage in a very short time when they feed on numerous plants, or when they gnaw on plastic water lines and sprinkler systems. Find out how to tell if it's a gopher mound and learn management tactics by reading the Pest Notes: Pocket Gophers.
18- Soil Solarization
Gardeners looking for a nonchemical way to control pathogens, nematodes, and weed seeds and seedlings may want to try soil solarization. This method is best done during the hot summer months. Learn how to use this technique by consulting the Pest Notes: Soil Solarization for Gardens & Landscapes.
19- Honey Bee Swarms
At times, large populations of between 5,000 to 20,000 honey bees can be found swarming around an urban area or a hive after taking up residence in your house. A swarm can be frightening but with correct management, it can be taken care of safely with the hive being saved. Learn how to get proper help by reading the Pest Notes: Removing Honey Bee Swarms and Established Hives.
20- Lyme Disease
Lyme disease can be transmitted to humans and pets from the bite of an infected western blacklegged tick. It can cause flulike symptoms that left untreated, may progress to arthritic, neurologic, or cardiac problems. Learn more about Lyme disease and how to safely remove a tick, and where to take a tick sample by reading the Pest Notes: Lyme Disease in California.