How to Prepare an Edible Garden
Few areas of the garden benefit from detailed preparation like the edible garden. The two most important components are putting the infrastructure in place (beds and irrigation) and using healthy soil. Although this can take time and work, it's worth making the investment upfront so you can enjoy years of successful growing and harvests.
Build healthy soil
Whether you choose to plant in the ground or in raised beds or containers, soil is the key to success. The majority of edible plants grow best in loamy soils, a mixture of clay, sand, silt, and organic matter. Since Marin’s soil is predominately clay, it retains water and nutrients but needs to be amended for improved aeration, drainage, and replacing nutrients that have been used or leached out.
To grow edibles:
Start with healthy soil that has a pH between 5.5 and 7.5, depending on what different plants need:
- Acid soil (pH 5.5) – berries
- Alkaline soil (pH up to 7.5) – asparagus, beans
- Wide-ranging soil pH – carrots, cucumbers, garlic, parsley, peppers, pumpkins, strawberries, and tomatoes
Evaluate your soil
Simple tests for drainage, texture, pH, and the primary macronutrients – nitrogen, phosphorus, and potassium -- will help you determine what type of planting situation (in-ground or raised beds) would work best. Learn how to evaluate your soil.
Address soil nutrient problems
Edible plants provide clues when there is too much or too little of one or more of the six macronutrients. Here's how to recognize and address soil nutrient problems in the vegetable garden.
| HOW TO BUILD SOILS FOR EDIBLES 1. Start with compost: Add 1 to 2 inches of compost twice a year, for example in spring and fall, about two weeks before planting. This replaces nutrients, restores microbiological activity, and maintains soil health. 2. Test and add amendments as needed and according to directions on the product. Add amendments 1 to 2 weeks before planting. 3. Grow cover crops in winter and dig the plants into the soil in spring. 4. Add a layer of mulch in summer (leaves, rice straw, or another layer of compost) to retain moisture, minimize weeds, and provide habitat for soil organisms that positively affect plant health. 5. Add organic matter such as compost, leaves, and aged manure. 6. Consider sheet mulching (also known as sheet composting) – This is a process to eliminate lawns and weedy areas while building healthy soil. It is best started in the fall to prepare for a spring garden, but it can be done anytime. Within six months, the sheet-mulched area will have decomposed to about half its height and will be ready to plant. |
MAKE YOUR OWN SOIL MIX Soil mix for starting seeds Soil mix for containers Soil mix for in-ground and raised beds |
Follow these guidelines for beds and paths
To keep your garden accessible and well-organized, use these general guidelines when laying out your planting beds.
Width and length
• Keep beds a maximum 4 feet wide so you can access them from both sides.
• If accessible from only one side, limit to 2 to 3 feet wide.
• Beds/rows may be as long as space and irrigation system allows.
Depth
• Prepare beds to a minimum depth of 6 inches.
• 12 inches is better for drainage, aeration, and root development.
Orientation
• In large gardens there may be advantages for directional orientation of rows and beds, but this is not usually the case in smaller backyard settings.
• Orient planting beds to suit your personal preference and plant your tallest plants on the northern side.
Path width
• Keep paths minimum 2 to 3 feet wide to accommodate wheelbarrow, ease of movement, etc.
Care
• Don’t walk on garden beds or they will become compacted and not drain.
Decide on types of beds
In-ground raised beds and rows:
• Inexpensive way to create a healthy spot for growing your favorite fruits and vegetables
• Easier and less costly to construct than boxed raised beds
• Easier to turn over
• Offer growing spaces in gardens where boxes do not fit
• Build in-ground raised beds where there is at least one-foot of soil with no underground limitations
Boxed raised beds:
• Help with tunneling pests, poor drainage, poor soil, and underground rock
• Reduce the possibility of erosion by containing soil
• Warm up earlier in the spring
• Can be built to heights that limit bending
• Reduce soil compaction
• More expensive to build but are a more permanent option
• Some types of raised beds are portable
Containers:
• Easy and convenient
• No digging and the container may be placed right outside the kitchen door
• Terrific for patio gardens, accent plantings and for plants that may be invasive such as mint
• May be placed on wheels and if tall enough, may be wheelchair accessible
• Most any container made of a material that holds up well when wet and left outdoors will do
• Be creative and take a trip to a salvage yard or hardware store for inspiration
• Learn more about growing edibles in containers
Straw bales:
While most gardeners grow crops using soil or raised beds, it's possible to grow vegetables without soil using straw bales.
• Readily available material for soilless gardening that will provide compost as a byproduct
• Allow gardeners to avoid growing in poor soils or locations where plant diseases may already be present
• Requires additional water and fertilizer to prepare them for gardening
• Have been used as a growing medium for vegetables for at least half a century in Europe
• Learn more about growing edibles in straw bales
Clear and clean your planting site
Once you've selected and assessed your site, evaluated your soil, and know what type of beds you want, you're ready to get going.
• If you discovered any hazards or limitations above or below the site, (electrical wires, limbs, plumbing, rocks, high water table, easements etc.) begin by addressing these issues.
• If you are unsure of the location of underground utilities, check with your utility company.
• If your site is sloping, construct terraces or level planting boxes to minimize runoff and erosion.
• If your site includes ornamental vegetation that shades garden beds or competes for irrigation, consider removing it.
• If your site is covered in weeds, remove them when soil is damp and appropriately discard invasive weeds such as Bermuda grass, purslane, morning glory, and Scotch broom.
Construct planting beds
In-ground raised bed:
• Remove weeds when soil is damp but not wet
• Use a digging fork to loosen soil to a depth of 6 inches
• Spread 2 inches of compost on top
• Add other organic matter such as straw and dried leaves
• Evenly scatter amendments such as blood meal, kelp meal, rock phosphate etc., to adjust nutrients as indicated by soil test
• Alternatively, premix compost with amendments and spread the premixed blend over the raised bed
• With a shovel or digging fork, blend the compost and amendments into the bed to a depth of 6 inches
• Mound soil above the height of the ground into rows 30 to 36 inches wide
• Build rows 2 to 3 feet apart and do not step on the beds
Boxed above-ground raised beds solve many problems.
Boxed raised beds
• Often made of 2-inch by 6-inch or 2-inch by 12-inch preservative-free redwood or fir
• Boxes are made in a variety of sizes; multiples of 4 are efficient as they reflect the 8-foot standard length of lumber
• Reinforce corners with 4-inch by 4-inch wooden posts or metal corner brackets
• Install half-inch hardware cloth on the bottom to deter gophers
• Once in place, fill boxes with potting mix or amended local soil
Build an irrigation system for edibles
Irrigation systems in edible gardens need to be flexible because crop locations change from season to season and water requirements differ based on what's growing and whether plants are grown from seeds or starts. It's tedious and time-consuming to change drip emitter locations every season. Overhead or micro-sprayers are good for starting seeds, but not always a good choice for established plants such as tomatoes, which don't appreciate wet foliage. In addition, it is important that the gardener can easily amend beds without having to navigate around irrigation tubing, emitters, etc.
HOW TO BUILD A FLEXIBLE DRIP IRRIGATION SYSTEM for an edible garden bed: Follow these instructions to create an irrigation system that allows you to irrigate your edible crops with drip (for starts and established plants) or spray (for seeds). Because this system only connects to ONE point, it can be "lifted" to allow unimpeded access to the bed for amending soil. 1. Identify one point of connection (to water) for a garden bed. 2. Starting and ending at that one point of connection, build a perimeter 'loop" using 5/8-inch irrigation tubing. It should outline the bed and only be "connected" at the one place. 3. Run 1/4-inch or 5/8-inch emitter lines from one end of the perimeter tubing to the other, 6 to 8 inches apart. Be sure to tap into the perimeter line at both ends. This should allow you to plant anywhere in the bed and access drip irrigation. 4. Install adjustable micro-spray risers to the perimeter tubing so that it's possible to "spray" the entire bed if necessary OR turn one or more off when not needed. (This is helpful when starting seeds outdoors.) |
Rules of thumb for irrigating edible crops:
• Use a drip system if possible.
• Begin the season with a garden bed moist to a minimum of 12 inches deep.
• Check moisture content of soil with your finger several times per week.
• Water when the top 1 to 2 inches of soil is dry.
• Avoid wet/dry cycles and keep your garden consistently moist.
• Occasionally check 8 to 12 inches deep to ensure that the deeper soil is also moist.
• Irrigate early in the day.
• Observe plants for feedback. Yellowing of lower leaves provide evidence of over watering. Wilting and browning at edges indicates under-watering.
• When hand watering, apply water directly to the bed until the soil “shines” for 10-15 seconds.
• Plants need approximately 1 gallon of water per week in peak heat so if you are hand watering 3 times a week, apply about 1/3 of a gallon per plant per watering.
• Shallow rooted plants such as lettuce and other greens may require frequent shallow watering while plants with deeper roots, such as tomatoes, may be irrigated less often.
• Learn more about irrigation.
BACK TO EDIBLES
> What Edible Gardens Need
> Best Choices for Marin
> How to Prepare
> How to Plant
> Edibles in Containers
> Planting Calendar
> Grow & Care Sheets for Vegetables, Herbs & Fruits
> Tips & Techniques
> How to Maintain
> Fruit Trees
> Top 20 Edible Garden Problems
> Cover Crops & Soil Enhancements in the Off-season
> Conserving Water
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Visit our EDIBLE DEMO GARDEN at IVC Organic Farm & Garden
July 2025: Vole Invasion
July 2025: Vole Invasion
Protecting the growing plants from hungry critters is an ongoing challenge in the Edible Demo Garden. Wire mesh is used extensively under planting beds and around the straw bales to discourage gophers. Yards of protective netting keep the birds and rabbits from eating young seedlings and ripening fruit. Through vigilance and determination, EDG volunteers have usually managed to reduce damage to crops from the vertebrate garden dwellers. However, this spring volunteers noticed that something was eating the summer squash plants in the straw bales in the area known as the “back 40”. Whatever it was had to be small enough to slip around and under the gopher-repelling wire mesh. Some little holes in the bales and on the ground nearby pointed to voles as the most likely culprits.
What are Voles?
Voles are small, chunky, ground dwelling rodents with short tails. They are also called meadow mice, but they are not mice or rats. They belong to a separate genus and are more closely related to lemmings. The most common of the five species of voles in California is the California vole, Microtus californicus. It is four to six inches long with grayish brown fur, a blunt nose, and small eyes and ears. Voles are herbivores. Although their favorite foods are grasses and herbaceous plants, they can cause extensive damage to edible crops.
How do you know if voles are in your garden?
Voles are active both day and night, but primarily around dawn and dusk. They hide in dense underbrush and in their shallow burrows, so they are not easy to spot. Voles are extremely prolific and mature rapidly with females bearing multiple litters per year.
Once you notice plant damage and suspect voles, look for burrows with numerous openings, about one to two inches in diameter, connected by narrow pathways. The pathways may be littered with droppings and plant fragments. Unlike gophers and moles, voles do not pile up soil around their burrows.
What can you do to control voles?
The first step to controlling voles is to make your garden less welcoming. Because they only like to travel a short distance to a food source, removing the vegetation they depend on for cover will discourage voles and prompt them to go elsewhere. Weeds and grasses provide hiding spaces, so creating a vegetation-free zone around a garden area will deter them. Unfortunately, they found both the food and cover they needed in the straw bales in the EDG garden.
In ideal circumstances, vole populations stay in balance, providing food for predators. Their lives are short, most living less than a year. They are snacks for owls, hawks, coyotes, foxes, and snakes. Populations also fluctuate with peaks every two to five years.
When vole populations are high and removal of vegetative cover and physical barriers are not sufficient to control them, snap-type mouse traps can be used with varying success. Traps should be placed at right angles to burrow pathways with the trigger end in the pathway so that voles will trip it as they pass over. Flooding or fumigating burrows does not usually work because of the shallow and open structure of the burrows. Poison bait, while effective, increases risk to pets, wildlife and humans and should never be used in edible gardens during the growing season.
What are the options for an organic edible garden?
While numerous home remedies and repellents have been suggested, none have been shown to be reliably effective against voles. Possible repellents include coffee grounds, cayenne pepper, castor oil, and garlic. Voles don’t like plants with strong odors and unpleasant tastes. They avoid plants in the allium family like onions and garlic and find daffodils, marigolds and castor beans distasteful. Several of these options were considered for the Edible Demo Garden. Coffee grounds were ruled out as not certifiably organic. Claims that sprinkling cayenne pepper around garden plants discourages voles prompted the EDG volunteers to plant hot peppers among the squash vines. Subsequently, damage to the plants appeared to decrease so maybe it worked, or possibly one of the snakes recently spotted in the garden is reducing the vole population.
Click here to learn more about voles.
January 2025: Natives in the Edible Garden
Native Plants Attract Pollinators and Invite Beneficial Insects
Native plants also invite beneficial insects that are natural enemies of vegetable garden pests. Beneficials such as hoverflies, lady beetles, and lacewings go where they find the herbivorous insects they like to eat. It doesn’t matter to them whether their prey is on an edible plant or a native. The natives keep the beneficial insects nearby, so they are there to control pests when the vegetable crops are planted.
Native Plants Improve Soil Health
Native plants support soil biodiversity by providing habitat for beneficial microorganisms like fungi and bacteria. Some can act as nitrogen-fixers to improve soil fertility. Natives with deep root systems can improve soil structure by creating channels through which water and nutrients can penetrate. When the roots and leaves of the native plants die back, they add organic matter to the soil reducing the need for soil amendments.
Native Plants are Low Maintenance
Natives don’t need fertilizing and require little watering once they are established. While some need deadheading and cutting back, it’s best to minimize the kind of tidying up that’s done in the edible garden. The native plants can offer a refuge for beneficial populations, providing them with undisturbed nesting and overwintering sites. Ideally the native plants attract enough beneficial insects and other natural enemies to maintain a healthy balance so that pests are kept in check.
Native Plants Add Beauty and Interest
Native plants bring unique beauty to the garden. The natives planted in the Edible Demo Garden were initially chosen to provide blooms throughout the year. Some flower early and bring color into the winter garden and others extend their blooming period into late fall. They add contrast to the flowering of the vegetables and fruit trees. Ceanothus ‘Concha’ now masks the compost bins with its copious cobalt blue flowers in early spring. Coast Aster, Aster chilensis, provides bright, daisy-like blossoms throughout summer and fall. Bees and hummingbirds enjoy the showy red tubular blooms of California fuchsia, Epilobium, into late fall. The goal to bring native plants into the Edible Demo Garden to provide year-round beauty has been achieved.
For more information on growing native plants, click here.
October 2024: Herbs Among the Edibles
The supporting cast of herbs in the Edible Demo Garden includes basil, oregano, thyme, lemon verbena, chives, Mexican tarragon, anise hyssop, chocolate mint, lavender, pineapple sage, and rosemary. Some are harvested and sold fresh at the Indian Valley Organic Farm and Garden farm stand and others are dried and offered as seasonings and teas. They are among the most reliable plants in the garden.
What is an Herb?
The word “herb” can be applied to any non-woody plant with leaves, seeds, or flowers used for seasoning, medicine, or fragrance. It’s the culinary uses that most commonly interest home gardeners. Herbs are considered different from spices based on the part of the plant that is used. Spices are derived from the roots, bark, fruit, berries, and seeds of plants. Some plants can be both an herb and a spice. Coriandrum sativum, also known as Chinese parsley, is called cilantro when the green leaves are used as an herb and coriander when the seeds are used as a spice.
Why Grow Herbs?
- Herbs make good neighbors with other plants and can be easily integrated into both edible and landscape gardens. They are attractive enough to do double duty as ornamentals.
- Herbs are cost-effective. They are inexpensive to grow and can be harvested in the amounts required for a recipe. No need to spend money at the supermarket on packages of herbs.
- The blossoms on herbs attract pollinators and other beneficial insects.
- Herbs are usually not bothered by pests and diseases. Some herbs have been shown to repel pests affecting companion plants. An example is the ability of basil to deter thrips from invading tomato plants.
- Deer usually leave herbs alone, especially those with strong tastes and scents.
- Herbs grow well in containers and are a good choice when garden space is limited.
Tips on Growing Herbs
Some herbs are started from seed while others are easy to grow from cuttings. Information on the growing needs of common edible herbs can be found at http://marinmg.ucanr.edu/EDIBLES/EDIBLES_GROW_SHEETS/
Check the upcoming events listings on this website to register for a hands-on public workshop on growing and using popular edible herbs. There will be a workshop held on the College of Marin Indian Valley Campus on November 2, 2024, from 10:00 am to 12:00 pm.