Cover Crops & Soil Enhancement

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This past month EDG volunteers created a small “patio” in the garden to demonstrate how edibles can be successfully grown in limited space. Too often gardeners are discouraged from growing edibles, believing that it takes a large back yard with room for long rows of plants. However, with the imaginative use of containers even a small deck, patio, or balcony can be converted into flourishing garden.

What are the basic requirements for growing edibles in small spaces?

Sun – Edibles need 4 to 6 hours of sunlight. Regardless of the size of the growing area, sun exposure is essential. Leafy crops such as lettuce and chard require at least 4 hours of sun per day and fruiting crops like tomatoes, melons, and beans need at least 6 hours of sunlight daily. It’s important to choose the sunniest spot on a deck or patio for an edible garden area.

Water – Container plants need water more often than those grown in the ground. The need to transport water to growing plants with buckets or watering cans can diminish the pleasure in growing edibles. While drip irrigation is ideal, a hose attached to a water source will suffice.

Containers – The possibilities for garden containers are numerous and range from commercial pots, planters, troughs, and bags to the creative repurposing of old pans and buckets, wooden crates, wheelbarrows, and, of course, wine barrels. A used filing cabinet with the drawers removed can make a great container for edibles. In the Demo Garden, a straw bale provides a patio container for yellow fin squash. Regardless of the type of container, good drainage is important so it may be necessary to drill holes to allow water to flow through easily.

Containers need to be deep enough to provide sufficient space for root growth. Depth requirements vary with the type of crop. Salad greens and some herbs can grow in 6- to 10-inch-deep containers while peas, eggplant, and peppers need at least 14 to 16 inches to develop a strong root system. Tomatoes in containers require a minimum soil depth of 18 inches.

Soil – The potting mix used in containers should be porous and fast draining, yet moisture retentive. A high-quality mix that contains compost and other organic matter is best. Garden soil is too heavy, difficult to keep evenly moist, and can harbor disease. Organic fertilizers should be added in frequent but light amounts as the watering that container plants require leaches nutrients from the soil.

Additional tips for small space edible gardening

Take advantage of vertical space – Trellises and stakes help tall and vining plants to grow upward. Use walls or fences as additional planting space by adding shelves, racks, or hanging baskets. A recycled step ladder is an inexpensive vertical gardening option. 

Avoid damage to structures – Use blocks or bricks under containers to prevent rotting wooden decks or stairs. Consider the weight of the soil and container when planting on a balcony.

Protect against animals and pests – Plants in containers are susceptible to the same pests as in-ground plants. Cages or netting might be necessary to protect against birds, squirrels, and other critters.

Don’t forget the pollinators – Adding a few flowering plants to a container garden can help to attract pollinators to the edibles and increase veggie and fruit production.
 

Click here for more information on growing edibles in containers.

When the winter rains end, it’s time for gardeners to focus on providing spring and summer edibles with the water they need to grow and produce. While hand watering may be the simplest way to adjust watering to the needs of individual plants, it’s not the most efficient means for getting the right amount of water to an entire garden.

Drip irrigation has proven to be the best option for home gardeners. It is particularly suitable for edible gardens because it delivers the water at the soil level and avoids water on the plant leaves which can lead to problems with mold and mildew. 

Drip irrigation is also waterwise, reducing loss by evaporation and runoff and maintaining a desirable balance of air and water in the soil through slow application of water to plant roots.

What can go wrong with drip irrigation?

Whether installed by professionals or as a do-it-yourself project, drip irrigation requires routine maintenance. It’s recommended that the lines be checked monthly when the system is operating. It is especially critical when the drip irrigation is first turned on in the spring. Here are some common problems to look for:

• Leaks. The dreaded geyser is a sure sign that there is a break in the line somewhere. It could be a dislodged emitter or a damaged line. Thirsty rodents like to chew on the tubing and lines can be unintentionally broken by shovels and spades.

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Finding a wet spot where there is no emitter can signal a problem in the supply line. If the line is buried, it will take some digging to find the leak. This was a recent problem in the Edible Demo Garden. The drip irrigation was installed some time ago and it was unclear which lines led to which bed. The search for this particular leak is still continuing.

• Blocked lines and emitters. Lines may get clogged, and emitters can be plugged by debris, mineral buildup, and algae. Pinched lines, especially the smaller feeder lines, can also be a problem. Periodically walking the circuit and checking flow from the emitters while the system is running is a good way to spot irrigation problems before plants start showing signs of distress.
• Low water pressure. Drip irrigation operates at 15-25 pounds per square inch (psi) which is much lower than sprinkler systems which can require up to 50 psi, and household systems running at 50-80 psi. A pressure regulator is needed to reduce the incoming household pressure to that for which the drip systems are designed. However, pressure in the lines can be lowered further by elevation gain, friction in the tubing, and long line lengths. It is recommended that 1/2” supply lines be limited to 200 feet in a single zone and the number of one gallon per hour emitters per line not exceed 200. If a drip emitter at the end of a line is not delivering sufficient water, it could be a low-pressure problem.

Fixing drip problems

With the right supplies, many common irrigation problems can be easily fixed. An emergency drip repair kit should include spare flow emitters of different sizes, connectors (both straight and elbow), line plugs, end caps, and tubing. It’s also handy to have a tool for cutting tubing, a punch to make holes in 1/2” line, and metal staples for securing the lines. The same supplies are useful when drip lines need to be added for new plants.

Lines can be flushed to remove debris, and clogged emitters can be cleaned or replaced. Small holes in lines can be plugged. Larger damaged sections in lines can be removed and connectors used to join the undamaged sections.

A water pressure test gauge, available at hardware stores, is helpful in determining if the pressure in the drip system is in the right range. Low pressure problems due to overly long lengths of supply line or too many drip emitters might involve changing the drip line layout or adding another zone to the system.

Controlling drip irrigation

Drip systems require control valves to direct water into the system. These are generally automated with an AC or battery powered controller/timer that makes it easy to set irrigation frequency and duration. These devices range from simple timers to more complicated “smart” controllers. All these devices include the option to run the system manually, allowing gardeners to conduct their periodic system maintenance checks.

Click here for more information on irrigation systems.

In January, the 2025 Marin Master Gardener training class was welcomed into the Edible Demonstration Garden for a discussion and demonstration on the use and care of garden tools. The right tools make the difference between gardening that is pleasurable and gardening that is a struggle. Your first experience with a garden tool might have been that pointed stick you used when digging in the dirt as a child. Now as a gardener, you are presented with an array of better tool choices, some essential for basic garden work and some designed for specific tasks. There are tools for pruning, tools for digging, tools for raking, and tools to make gardening easier. Here are some of the more popular tools in those categories.

Pruning Tools

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  Hand pruners are the favorite tool for most home gardeners. They are the tools used most often for cutting and thinning small branches to maintain plant health and appearance. They are also used for cutting flowers and harvesting vegetables. By-pass pruners, which work like scissors, are best for making clean cuts on living plants. Anvil pruners crush branch tissue and are good for removing and cutting up dead branches.

• Pruning saws are used to remove branches larger than what hand pruners can remove. They can have a fixed or folding blade.
• Loppers are long-handled by-pass pruners that can help access higher and hard to reach branches. The long handles also provide leverage to enable pruning thicker branches.

Digging Tools

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  Trowels are essential for digging, planting, potting, and weeding. A trowel is a spade-shaped hand tool with a slightly scooped blade.

• Garden knives are a type of trowel with a sharp narrow blade and a pointed end. One blade edge is usually serrated. Hori-Hori garden knives are a Japanese design that has proven to be so useful for digging and weeding that the name is often applied to any type of garden knife.
• Shovels and spades are long-handled digging and soil lifting tools with the shape of blade and the length of the handle determining their particular uses.

Raking Tools

• Rakes are useful for cleaning up leaves, removing debris, and spreading out soil amendments like compost and mulch. Hand rakes are great for getting into small spaces. Rakes with flexible, fan-shaped tines work well for cleaning up lighter debris and are sometimes called leaf rakes. Garden rakes have larger stiff metal tines and are intended for heavier use in soil or larger debris.
• Forks are used for raking out stones and weeds. Like a dinner fork, a garden fork has four strong tines which can push easily into the ground and enable it to double as a digging tool for loosening and turning over the soil.

Gardening Comfort Tools

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  Gloves provide the hand protection every gardener needs. They are a barrier against pricks, cuts, abrasions, blisters, insect bites, and other skin irritations. While most gardeners don’t mind getting their hands dirty, getting jabbed with a nasty thorn is not only painful, but it can also lead to serious infections. There are many types of gloves to choose from depending on the type of protection required. Most important is that they fit well and are comfortable to wear.

• Kneelers cushions protect the knees when planting, weeding, and performing other low to ground garden tasks. Kneelers made of rectangular shaped heavy foam are the simplest type. However, kneelers with handles that are lightweight and easy to fold up can make the up and down movements around the garden easier. Some even flip over to form a bench.
• Ergonomically modified tools can help gardeners get more done with less effort by enabling good body alignment and reducing joint strain. Grips should be comfortable to hold and keep hands and wrists in natural positions. Handles should be the right length to enable good posture without excessive bending and twisting.

Tool Care

Tools need to be kept clean, sharpened, in good repair, and organized to keep them working well. Surface dirt and dried sap should be brushed or washed off after each use. Periodically applying a light layer of oil will reduce rust. Pruners need regular sharpening and should be sanitized with a 10% bleach solution following contact with diseased plant material. Storing tools in dry place where they can be easily accessed will ensure they are ready for work when you are.

Click here to learn more about choosing and caring for garden tools.

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.

Planting cover crops

There are many advantages to planting cover crops. Cover crops, sometimes referred to as “green manure”, are an excellent way to protect and improve soil. They increase organic matter, suppress weeds, prevent damage from wind and water erosion, and support beneficial insects and earthworms. Plus, they can look attractive while nurturing the garden.

Two different cover crops were chosen for the Edible Demo Garden. Fava beans were planted in several of the garden beds and in the straw bales used for the summer crops. The latter is an experiment to determine if there is sufficient residual fertility in the straw bales to support another crop. In order to aid in germination and enhance their nitrogen fixing effects, the fava bean seeds were soaked in an inoculant containing rhizobacteria prior to planting. As an alternative cover crop, a green manure mix of bell beans, field peas, and purple/hairy vetch was planted in some of the raised beds. Past experience with crows eating the sprouting seeds necessitated the use of compost, straw, and protective netting to give the cover crop seedlings a fighting chance. The effectiveness of the different cover crops will be tested in spring when it is time to plant again.

Allowing beds to remain fallow

Click here for more information on cover crops and soil enhancement in the off-season.

Tomatoes are among the top summer crops in the Edible Demo Garden and each year there are decisions to be made about which varieties to grow. Since there are reported to be over 10,000 varieties of tomatoes, it’s important to narrow down the selection considerably and plant only those varieties that grow well in Marin and are appealing to consumers. However, even within those broad parameters, many choices can be made. The Marin Master Gardeners typically offer sixteen varieties in their annual tomato plant sales. These are the varieties that have proven over the years to be the most popular with customers. Each year one or two new varieties may be offered to replace some that have not fared so well in terms of sales or customer reviews. Choices about new varieties are usually based on members’ recommendations.

The Tomato Experiment

This spring the Edible Demo Garden and the Edibles Guild launched a collaborative experiment to determine which of seven tomato varieties not previously sold in the tomato market, would be most successful in Marin’s different growing conditions. The experiment involved adopting out 132 plants grown in the Indian Valley Organic Farm & Garden greenhouse to 37 Marin Master Gardeners willing to try growing them in their own gardens. The seven varieties were:

• Costoluto Genovese – a classic red Italian heirloom
• Bicolor Marvel Stripe – a marbled red and gold heirloom
• Moonglow – a bright orange heirloom
• Mortgage Lifter – a large meaty red heirloom
• Magic Bullet – an elongated cherry-sized open pollinated variety
• Pink Berkeley Tie Dye – a wine-colored open pollinated variety with green stripes and pink flesh
• Amish paste – a small bright red heirloom best used for sauces

The tomato adopters agreed to submit data describing their experiences growing the trial tomatoes. They recorded the garden type, location, and microclimate, when the tomatoes were planted, how they were cared for, and when the first tomato was harvested. Then they subjectively rated the tomatoes on yield and taste. Finally, and most importantly, they answered the question – “would you grow this variety again?”.

Which varieties had the best results?

What matters most when choosing tomatoes to plant

One of the most important factors to consider when choosing a tomato variety is the microclimate in the growing location. Tomatoes need sunshine and warm soil. All the experimental tomatoes required temperatures above 65 degrees and some preferred 75 degrees. During a typical spring, in most areas of Marin, around May 1^st is when the temperatures are best for planting tomatoes. Tomatoes planted before the air and soil are sufficiently warmed, will sit idly by until the conditions are right. Conversely, tomatoes don’t like extreme heat and will stop production during heat waves like those experienced in parts of Marin this summer.

Linked to microclimate are days to maturity. This is the average time it takes for the first ripe fruit to develop in ideal heat conditions. Magic Bullet, Pink Berkely Tie Dye, and Costoluto Genovese are considered mid-range, requiring 70 to 80 days to mature. The others are late maturers, needing more than 80 days to produce ripe fruit. Bicolor Marvel Stripe takes 95 days to mature. In cool areas of Marin, there may not be enough warm days for some late maturing tomato varieties to reach full production.

Click here for more advice on selecting and growing tomatoes.