Protect and Replenish Your Garden Soil with a Cover Crop

What do you do with your garden beds after you’ve harvested the season’s fruits, vegetables, and flowers?

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By: Valerie Rose, Skagit County WSU Extension Master Gardener

Don’t leave the soil exposed to winter rain and wind – protect your precious garden soil with a cover crop. Garden crops draw nutrients from the soil, and cover crops replenish these nutrients. Think of it as home-grown fertilizer.

Cover crops are sometimes known as green manures. Farmers spread composted animal manure on fields, a traditional fertilizer source, replenishing soil nutrients following the harvest. Cover crops are a green, plant-based fertilizer that feeds the soil without animal products, hence the term ‘green manure.’

Cover crops do many important jobs at once, working quietly in the soil when it’s too cold for even the heartiest gardeners to lift a trowel. They include many species of plants: grains, grasses, and legumes (beans and peas). These versatile plants can suppress weeds, retard erosion, add organic matter, and store nutrients for future plants. Organic matter builds better soil structure and fertility, increasing water retention, drainage, and aeration.

Cover crops grow food for the soil instead of ingredients for a salad. When planted in autumn, cover crops are dug into the garden bed in the spring. Once tilled back into the soil, cover crops break down, adding nutrients and organic matter, nourishing next year’s garden. They also provide necessary food for earthworms and microorganisms. Cover crop plants are genuinely masters of multi-tasking.

Many Varieties to Choose From
You have many choices of cover crop plants with differing benefits. Adding and replenishing nitrogen, an essential plant nutrient, clover is a real gift. Clovers are nitrogen-fixers; they take atmospheric nitrogen from the air through the plant leaves and convert it into a form that plants can use. These generous plants store this vital nutrient in small nodules on the roots with the help of soil bacteria called rhizobia. When the plants decay in the ground (or are tilled into the soil), the nitrogen is available to feed other plants. Gardeners should plant crimson clover from September through mid-October and till it under in the spring. Crimson clover is this gardener’s favorite cover crop; I till under most of the plants, leaving a dozen or two to flower. The glorious red blooms are a welcome food source for pollinators in the spring and make a long-lasting cut flower.

Austrian field peas are another great option. This cold-hardy overwintering pea is an excellent choice for cooler, poorly drained soils, which describes many garden beds we know. You can sow this nitrogen-fixing pea as late as the end of November. Dig the plants into the ground in late April or early May in the spring.

Clovers and peas benefit from ‘inoculation’ – coating the seeds with nitrogen-fixing bacteria before planting. Doing this increases the amount of nitrogen each plant can retain. Most seed dealers sell small packets of inoculum, which are actually bacterial spores of rhizobia.

The inoculum and seeds are an easy, inexpensive way to nourish your hungry soil.

Buckwheat roots loosen the topsoil while accessing phosphorus within the soil, which is then stored in the plant’s tissues returning phosphorus to the soil for the next crop. Photo: © Adobe Stock

Some Choices of “Green Manure” Cover Crops

Crop	Planting Time	Spacing	Seeds/100 sq. ft.	Comments
Crimson Clover	Sept. – mid Oct.	Broadcast	1-4 oz.	Legume* – Does poorly in poorly drained, acidic, infertile soil. Good for undersowing. Avoid other, perennial clovers, such as red clover.
Vetch	Late Aug. – mid Oct.	Broadcast	5-10 oz.	Legume* – Soak seeds overnight before sowing.
Field Peas	Late Aug. – Oct.	Broadcast	10-12 oz.	Legume* – Does reasonably well in poorly drained or infertile soil. Very hardy. Matures later than crimson clover.
Fava Beans	Late Oct. – early Nov.	6″-8″	12-14 oz.	Legume* – Soak seeds overnight before sowing for quicker germination. Large plants, lots of organic matter, nitrogen for soil. Not very hardy.
Cereal Rye	Late Sept. – Oct.	Broadcast or 5″ spacing	5-10 oz.	Produces lots of biomass. Harder than legumes to chop up. Breaks down more slowly. Roots improve soil structure. Chop before stalks turn brown.
Winter Wheat	Late Sept. – early Oct.	Broadcast or 5″ spacing	5-10 oz.	(see Rye comments)
Buckwheat	June-Aug.	Broadcast	3 oz.	Good summer green manure. Doesn’t need lots of water. Attracts beneficial insects. Not winter-hardy.
Tyfon	May – Sept.	Broadcast or transplant 4″	1⁄2-1 oz.	Cabbage family. Do not follow with same family crop. Edible greens and roots.
Corn Salad	Sept.	Broadcast	1 oz.	Good salad greens in winter. Allow to grow in early spring before chopping.

Retrieved from: https://s3.wp.wsu.edu/uploads/sites/2053/2015/09/list-of-crops-with-garden-coverage.pdf

Don’t Let Them Go To Seed
Cover crops should be tilled or dug into the soil before going to seed. Tilling or digging in is especially important when planting buckwheat, which is sown in summer. Clare Sullivan, a field crops expert for the Oregon State University Extension Service, notes, “The fast growth and dense canopy smothers annual weeds, protects the soil from erosion, and helps conserve soil moisture. The abundance of blossoms attracts pollinators and beneficial insects, and in a pinch, buckwheat can be added to a bouquet.”

Buckwheat roots loosen the topsoil while accessing phosphorus within the soil, which is then stored in the plant’s tissues. “When buckwheat residues are returned to the soil, the phosphorus becomes available for the next crop,” Sullivan said.

Cover Crops on Farms
Gardeners and farmers alike benefit from planting specific crops. Many farmers renew the health of their soil with cover crops. They may plant entire fields or in rows between orchard fruit trees. The Skagit Conservation District’s Cover Crop Grant Program helps eligible farmers purchase seed.

Farmers may plant cereal grasses like oats, barley, or rye. Rye is one of the most commonly grown cover crops on Northwest farms. This crop is vigorous, very cold-hardy, and can germinate and establish in cool weather. Rye grows rapidly in the spring, so it can become difficult to turn under by the time gardeners are ready to work their gardens. Mowing or weed whacking may be necessary before incorporating a heavy cover crop of cereal rye.

Livestock can enjoy grazing on cover crops such as triticale or winter rye. Even a variety of radish is used as a cover crop! Unlike radishes grown in vegetable gardens, the Forage radish loosens soil rather than enhancing a salad. Also known as “tillage radish,” their large roots “till” deep into the ground, naturally aerating the soil. Forage radishes also provide excellent food for wildlife.

Adding a cover crop to your garden is a small task with large benefits. “It seems really unlikely that you’re planting a seed in October that’s going to somehow magically do something good for you,” says David Kidwell-Slak, the National Plant Materials Center Manager for the National Resource Conservation Center. “[But] they provide a lot of benefits without much effort. It makes a pretty amazing addition to the garden.”

REFERENCES AND RESOURCES:
Cogger, C., Benedict, C. and Andrews, N. (2014) Cover Crops for Home Gardens West of the Cascades. Washington State University Extension Publication FS111E. https://pubs.extension.wsu.edu/cover-crops-for-home-gardens-west-of-the-cascades-home-garden-series

McNiff, N. (2022) Cover Crops Benefit Both Commercial Farmers and Urban Gardeners. Farm Production and Conservation Business Center, USDA. https://www.farmers.gov/blog/cover-crops-benefit-both-commercial-farmers-and-urban-gardeners

Allison, J. (3/19/21) Conservation District Program Helps Skagit Farmers Plant Winter Cover Crops. Skagit Valley Herald, GoSkagit. Retrieved from: https://www.goskagit.com/news/local_news/conservation-district-program-helps-skagit-farmers-plant-winter-cover-crops/article_5021e864-1dc7-5490-abf2-f69cca34828d.html 

ABOUT THE AUTHOR:
Valerie Jean Rose became a Master Gardener in 2009. A former journalist, she enjoys playing with words and plants-particularly her own vegetables.

There is still time
to apply to become
a Master Gardener in 2025
Questions about becoming a Master Gardener may be directed to: Skagit County WSU Extension Office, 11768 Westar Lane, Suite A, Burlington, WA 98233; by phone: 360-428-4270; or via the website: https://extension.wsu.edu/skagit/mg/
Sample Apples and Pears at NW Fruit
On Saturday, October 12 NW Fruit will hold its Sample the Apple and Pear Harvest Day. It is open to members, but anyone can attend by paying a $25 annual membership fee that day. Dr. Cameron Peace of WSU’s School of Horticulture (Pulman) will speak about heritage apple varieties and using DNA to identify varieties. There will be a tour of the many pioneer varieties in the garden and a chance to taste dozens of delicious cultivars thriving in the garden. Bags or boxes of ladder-picked fruit will be available for members to take home in addition to other fruit. Go to the website https://nwfruit.org/apple-pear/ to read more about this event.

Season Extenders

These practices can extend the growing season by as much as two to four weeks.

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By Hallie Kintner, Skagit County WSU Extension Master Gardener

Every spring and fall gardeners commiserate over what feels like a short growing season. Our area has between 200 and 230 growing days,¹ whereas locations in southwest Washington can have as many as 50 additional growing days. Here in Skagit County gardeners successfully extend the growing season by using what is called season-extending practices. These practices are quite common in colder climates and can lead to larger plant starts in the spring, earlier harvests, and a longer growing season in the fall. Some add to the growing season as much as two to four weeks in both the spring and the fall.²

This cover stores flat and pops up to form a cylinder around a container or a plant to keep it warm and protect against the wind. The top mesh unzips for ventilation and rainfall. Photo © Hallie Kintner

Spring and fall weather in our area can see nighttime temperatures drop into the 50° F and even into the 40° F range, making the soil temperatures fall below the optimum for some vegetables and early-season fruits like strawberries. Few plants grow well when temperatures drop below freezing.

To extend the growing season and enjoy the bounty of the garden longer, these are some of the methods Skagit County WSU Extension Master Gardeners use in the Discovery Garden on Hwy 536 west of Mount Vernon.

Raised beds
In addition to the many advantages raised beds provide, they extend the garden season. The soil in raised beds warms earlier in the spring and maintains its warmth later in the fall.

Cold frames
Resembling low-walled raised beds, cold frames are bottomless boxes with clear glass or plastic lids attached by a hinge. The lid can be opened or closed depending on the temperature. Cold frames protect plants from wind, rain, ice, snow, and cool temperatures. The hinged lid is opened on warmer days when it becomes too hot inside for the plants and closed again in the evening. Cold frames also have a long history of being used for starting seeds or hardening off plants before planting in the garden. ³

Cold frames should be placed on well-drained soils with southern exposures. Interior temperatures are warmed by the sun heating the frame and soil. With the addition of an external heating element like electric heating cables, a cold frame can become a hot frame.

Cold frames work especially well for growing cool-season crops like lettuce, radishes, and spinach in the spring. Start cool season vegetables in late summer with the cold frame lid open and then, as summer moves into fall and the nights become cooler, close the lid to retain warmth.

Milk jugs or other plastic containers can be used as miniature greenhouses for starting seeds in winter, getting a jump on spring planting. Our 12/22 blog explains this technique at https://www.skagitmg.org/winter-sowing-technique/

Cloches
These covers act as miniature greenhouses for individual plants. The word “cloche” is a French word meaning a bell-shaped cover. A cloche can be a glass jar or a translucent plastic milk jug, cut in half and placed over an entire plant. As with cold frames, when using a cloche be certain to allow ventilation as the temperature increases. Glass or plastic cloches can protect against wind, weather, and even snails and slugs.

Water-filled tomato protectors are another type of cloche. They are plastic cylinders consisting of water-filled tubes that are placed teepee-style around individual young plants. The protectors act like an igloo to protect heat-loving transplants like tomatoes, peppers, cucumbers, melons, and eggplants early in the season. The sun warms the water in the cells during the day, and the heat is released slowly during the night. The tomato protectors can be removed when the plants grow outside the cylinder and the weather improves. They can protect down to about 16° Fahrenheit. ⁴

These row covers in the Discovery Garden allow rain to go through them while protecting against cold temperatures and insects. Photo © Kay Torrance
Floating row covers
Row covers are synthetic fabrics placed on top of a plant row or raised bed. They allow rain to go through them while protecting against cold temperatures and insects.⁵ Unlike the cold frames and cloches, row covers don’t protect against deer and other critters. Use garden staples or soil pins to anchor row covers, keeping them in place during windy conditions.

The synthetic fabrics used for row covers are available in different thicknesses corresponding to varying levels of light transmission and cold insulation. Light-weight row covers transmit 80%-90% of the light but are easily torn and do not protect against frost. Medium-weight row covers protect to 28° Fahrenheit and transmit 85% of available light. Heavy-weight row covers transmit only 35-50% of the light but can protect to 24° Fahrenheit. Heavy-weight covers are best for frost events; remove them after the temperature rises. 

If the plants you are growing need pollination by insects, such as cucumbers, squash, and pumpkins, remove the covers after the plants bloom so that the insects can reach the flowers.

Unfortunately, strong winds can blow away floating row covers and damage tender plants. To solve this, many gardeners attach the fabric to temporary arched structures. These supported row covers consist of row cover fabric draped over and attached to bent tubes or rods, forming a hoop tunnel or a ribbed framework. The ends of the row cover are opened to allow ventilation to enter where the fabric is gathered and secured. The tunnel can be opened on warm, sunny days and then closed overnight.

Tunnels can be low, only 2-3 feet tall for a row of low-growing plants like greens or a raised bed.⁶ Low tunnels are best for low-growing, heat-tolerant plants including strawberries, melons, herbs, certain cucumbers, and greens.

If fungal diseases are an issue, plastic sheeting can be draped over the hoops to replace the row cover fabric. The resulting tunnels protect plants from the rain⁶ but the plants will require irrigation and will be warmer than the row cover fabric.

Tunnels can also be tall enough for an adult to stand (high tunnels). Many commercial high tunnels are too large for home gardeners because they are meant for the plants to be grown in the ground. ⁷ High tunnels for home gardeners are often temporary structures constructed of plastic or fabric draped over a metal ribbing and attached to a short, wooden wall as a foundation.  Both high and low tunnels are typically unheated and without access to electricity.

Gardeners often get creative when it comes to protecting early season tomato starts. Collected on a garden cart, these starts enjoy a sunny spring day, and then are easily moved back into the garage in the evening to protect from cooler overnight temperatures.Photo © Kay Torrance

By loosely laying plastic over the garden cart in the evening, some of the heat captured is heat is retained into the evening hours. Photo © Kay Torrance
Greenhouses
The king of season extenders is the greenhouse. These permanent structures consist of glass or plastic panels built into wood or metal frames usually on a foundation. To provide a warm, moist environment, greenhouses need power for ventilation and lights, drainage, and benches along with garden equipment. A greenhouse is a major investment of resources and requires careful planning. ³  

The purpose of all-season extenders is to protect plants from the cold weather by trapping heat from the sun, keeping plants and soil warmer as the outside temperatures drop, and protecting them from the elements. Try some of the techniques outlined here and you will reap the benefits from an extended growing season.  

REFERENCES:

1. McMoran, D. (2015) Skagit County Washington State University Extension Agricultural Statistics. https://extension.wsu.edu/skagit/agriculture/
2. Steil, A. (2023) All about cold frames. Iowa State University. https://hortnews.extension.iastate.edu/all-about-cold-frames
3. Hamilton, M., Werlin, J., Boone, K., & Austin, G. (2022) An introduction to season extension for high-altitude, short-season gardens. University of Idaho Extension BUL936, September 1, 2022. https://www.uidaho.edu/extension/publications/publication-detail?id=bul0936
4. Hodges, L., (2007) Early Season Extension Using Hotcaps. University of Nebraska-Lincoln Extension G1745.  https://extensionpublications.unl.edu/assets/pdf/g1745.pdf
5. Parker, J., Miles, C., Murray, T., & Snyder, W. (2012) How to install a floating row cover. Washington State University Extension Fact Sheet FS089E, 2012. https://pubs.extension.wsu.edu/how-to-install-a-floating-row-cover-home-garden-series

ABOUT THE AUTHOR:

Hallie Kintner is a Skagit County WSU Extension Master Gardener, Class of 2020. She is a member of the Community Outreach and Education Committee and enjoys working in the vegetable garden at the Discovery Garden on Hwy 536 west of Mount Vernon.

 

 

 

Questions about home gardening or becoming a Master Gardener, may be directed to: Skagit County WSU Extension Office, 11768 Westar Lane, Suite A, Burlington, WA 98233; by phone: 360-428-4270; or via the website: https://extension.wsu.edu/skagit/mg/

© Pexels.com

The Health Benefits of Gardening

As our gardens move towards winter we pause to realize what a gift gardening is to us all. 

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By Kathy Wolfe, Skagit County WSU Extension Master Gardener

Most gardeners know from experience the benefits they feel from working in their gardens. These moments are what keep us going back season to season, year after year, whether it is the joy of nurturing our landscapes, the creativity of design, the bounty of our vegetable harvest, or the camaraderie of sharing a goal working with our children, family, or gardening friends.

As author Sue Stuart-Smith writes in The Well-Gardened Mind: The Restorative Power of Nature, “gardening is more accessible than other creative endeavors, such as painting and music, because you are halfway there before you start; the seed has all its potential within it – the gardener simply helps unlock it.”

Gardening increases social connections and increases the size of your support group. © Nancy Crowell Photography

Gardening rewards us by igniting all of our senses. © Nancy Crowell Photography

Gardening rewards us by igniting our senses. The scents of flowers and herbs wafting through the air, the calls of birds and bees going about their daily business, the taste of the season’s first cherry tomato straight off the vine, the dazzling rainbow of colorful flowers, or the feel of earthiness in the soil, as we dig up the dirt. All contribute to our feeling of calm and connectiveness.

In addition to the intrinsic feelings gardeners share, scientific studies have found other benefits that can help improve physical and mental health. This has led to the forming of groups that work with physically and mentally disabled individuals using techniques practiced in gardening to improve their lives. Many undergoing physical rehabilitation have improved mobility of limbs and coordination. Those struggling with their abilities to focus, such as attention-deficit / hyperactivity disorder (ADHD) patients, can learn over time to concentrate on the task at hand. Studies have found people experiencing mood disorders or post-traumatic stress disorder (PTSD) can alter EEG recordings, and reduce stress, fear, anger, and sadness as well as blood pressure by working with plants.

Gardening provides the camaraderie of sharing a goal working with our children, family, or gardening friends. © Nancy Crowell Photography

Gardeners know from experience the benefits they feel being in a gardens. These moments are what keep us going back season after season, sharing the joy of a nurtured landscape. © Nancy Crowell Photography

Let’s look at some of the findings of gardening’s benefits for all of us:

Improving mood – Focusing on immediate tasks and details can calm the mind away from negative thoughts and feelings, giving us a more peaceful and content frame of mind.

Self-esteem boost – Seeing plants grow and thrive under our guidance leads to feelings of accomplishment for our efforts.

Improvement in attention span – Paying full attention to a single activity can be difficult at times in this age of technological bombardment. Gardening helps us concentrate on what is right in front of us without getting distracted. This concentration can transfer to other situations over time. Studies show that outdoor activities are a benefit to everyone.

Provides exercise – Through digging, weeding, raking, and hauling, our bodies move several different muscle groups which help improve heart rate, muscle strength, immunity, and overall mental well-being. Reducing anxiety and depression can be a result.

Learning resilience – Not everything in the garden goes as planned. Learning from our mistakes and pushing forward to rectify problems or begin the project anew helps forge stronger resolve to get good results.

Encourages social bonds – Working at a community garden or in a group fosters teamwork and cooperation to achieve shared goals. By increasing social connections, you may increase the size of your support group and also help you identify as being a part of the general gardening community.

Nothing quite beats the satisfaction of harvesting vegetables grown in your own garden. © Ruth Sutton

Seeing plants grow and thrive under our guidance leads to feelings of accomplishment for our efforts. © Nancy Crowell Photography

Horticultural Therapy has been documented in ancient times and practiced in America since the 19th century when Dr. Benjamin Rush, who is recognized as the “Father of American Psychiatry,” first documented the positive effects that working in the garden had on mental illness patients. In the 1940s and 1950s gardening was used to help hospitalized war veterans transition from both mental and physical traumas experienced during their service.

Gardens have been used in prisons and mental health facilities to help participants make connections through the soil as they witness the seeds they planted emerge and thrive through their efforts. Children’s gardens, particularly in deprived areas of large cities, can provide a needed calming environment and help

teach students where their food comes from. Studies have shown these gardens can be most beneficial to children who sometimes get lost in the regular classroom – those who are unmotivated, have special needs, or experience behavioral problems.

The American Horticultural Therapy Association offers accredited certificate coursework for becoming a professional in this field. Their criteria for being a horticultural therapist include having a minimum of a bachelor’s degree in horticultural therapy, or additional coursework in plant science, human science, and horticultural therapy. Members must complete a 480-hour internship in horticultural therapy and professionally register through their organization.

Even as our gardens slowly move into dormancy over the winter, we are still engaged with looking backward at the successes and challenges of the past year and at the same time are invigorated by planning changes, improvements, and additions we want to implement in the year ahead. What a multifaceted gift gardening is to us all!

 

REFERENCES:

Gillihan, S. 10 Mental Health Benefits of Gardening. Psychology Today [Internet] 2019 June 19. https://www.psychologytoday.com/us/blog/think-act-be/201906/10-mental-health-benefits-gardening

Davis, D. Hayes, J. What Are the Benefits of Mindfulness. Continuing Education (CE) Psychology [Internet], 2012 July/August Vol. 43, No. 7. https://www.apa.org/monitor/2012/07-08/ce-corner

WebMD Editorial Contributors. How Gardening Affects Mental Health. Web MD [Internet] 2021 Oct. 25. https://www.webmd.com/mental-health/how-gardening-affects-mental-health

Schattenberg, P. The Positive Effects of Gardening on Mental Health. Texas A&M AgriLife Communications [Internet] 2022 May 18. The Positive Effects Of Gardening On Mental Health – Texas A&M Today (tamu.edu)

Hall, C. Knuth, M. An Update of the Literature Supporting the Well-Being Benefits of Plants: A Review of the Emotional and Mental Health Benefits of Plants. Journal of Environmental Horticulture. Meridian Allen Press [Internet] 2019 37 (1): 30-38. https://meridian.allenpress.com/jeh/article/37/1/30/430948/An-Update-of-the-Literature-Supporting-the-Well

Horticultural Therapy. American Horticultural Therapy Association. [Internet]. https://www.ahta.org/horticultural-therapy

Stuart-Smith, S. The Well-Gardened Mind – The Restorative Power of Nature. Simon & Schuster 2020.

 

ABOUT THE AUTHOR:

Kathy Wolfe has been Skagit County WSU Extension Master Gardener since 2002. She is co-manager of the vegetable garden at the Discovery Garden on SR 536 west of Mount Vernon.

_________

Questions about home gardening or becoming a Master Gardener, may be directed to: Skagit County WSU Extension Office, 11768 Westar Lane, Suite A, Burlington, WA 98233; by phone: 360-428-4270; or via the website: https://extension.wsu.edu/skagit/mg/