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.

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.

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. 

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.