Lettuce is generally considered to be a cool-season annual, but with a little advanced planning and some judicious plant selection, Marin gardeners can enjoy home-grown lettuce throughout the year. Our temperate climate makes it possible to modify the growing conditions for lettuce and enable the plants to thrive in all seasons. That’s good news for salad lovers!

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Seasonal Challenges for Growing Lettuce

Lettuce grows best in 45-to-73-degree temperatures. Heat above 80 degrees causes most varieties to bolt (produce flowers) and become bitter. Temperatures below freezing often result in plant damage. Additionally, the shorter winter daylight hours slow or pause growth.

Volunteers in the Edible Demo Garden like a challenge, so learning how to grow a steady crop of lettuce in every season was an ideal project. Lettuce has become a popular crop at the Indian Valley Organic Farm & Garden. Although the success of the project was evident quantitatively in the over 260 heads of lettuce harvested since July 1, 2025, the qualitative gains, in terms of knowledge and experience, are immeasurable. Some key strategies identified for lettuce growing success include selecting the best varieties, succession planting, and managing environmental conditions.

Selecting the Best Varieties

Lettuce varieties are divided into four categories: crisphead, butterhead, looseleaf, and romaine. Crisphead is the iceberg lettuce found in grocery stores. It takes longer to develop and is difficult to grow in hot climates. It’s not a popular choice for home gardeners and is not a variety grown at the Edible Demo Garden.

Butterhead lettuce, also called bib lettuce, is more heat-tolerant. Varieties of butterhead that have thrived in the Edible Demo Garden are ‘Red Cross’ and ‘Aunt Mae’s Bibb’. Both are heat-tolerant and slow to bolt. ‘Red Cross’ has bright red and green leaves making it especially appealing in summer salads.

Loose-leaf lettuces include the “cut and come again” varieties with different leaf shapes, some described as oak leaf-shaped. They can be harvested by taking the outer leaves and leaving the central leaves to mature for future picking. ‘Smile’ is a bright green oakleaf variety that has performed particularly well in the Edible Demo Garden. Other loose-leaf varieties grown in the garden are ‘Morgana’ and ‘Bijella’. ‘Muir Summer Crisp’ is a dense, wavy-leafed variety that is exceptionally heat-tolerant and slow to bolt. 

Romaine lettuce, such as ‘Little Gem’ also grows well in the Edible Demo Garden but takes longer to mature and is not as heat-tolerant as other types. As a result, it is not as productive in the garden as the butterhead and loose-leaf varieties.

Succession Planting

A year-round lettuce harvest requires always having lettuce growing in different stages. That means starting seeds indoors or direct sowing in beds at the same time mature lettuce is being harvested. A volunteer day in the Edible Demo Garden might involve sowing lettuce seeds in cells to germinate in the greenhouse, planting the starts that are now ready in the garden beds, and harvesting the fully grown heads of lettuce for distribution in community-supported agriculture boxes. Intervals for succession planting vary according to the crop, but sowing seed every two weeks is about right for lettuce.

Managing Environmental Conditions

Lettuce requires proper watering and protection to thrive. Frequent, light watering is important for shallow-rooted lettuce. Too little water will stunt and toughen the plants, and too much water causes root rot. Mulching around the plants helps maintain moisture and keeps the leaves off the ground.

Protection from heat and pests can be challenging. Lettuce appreciates some shade in the summer, so planting it next to taller plants or using shade cloth can reduce the chances of it bolting. Animals and insects love lettuce too. In the Edible Demo Garden, lettuce beds are covered in protective netting to deter hungry birds, rabbits, and other critters. Mesh wire is placed under the beds to stop invasions from below. Even that didn’t prevent gophers from tunneling through the wood on the side of one of the beds and feasting on a few heads of lettuce. The protective netting also provides some shelter from the sun and flying insects. Aphids, earwigs, and slugs can still be a problem, so it pays to be vigilant and remove them as soon as they are discovered.

Click here for more information on growing lettuce:

https://ucanr.edu/site/uc-marin-master-gardeners/documents/lettuce

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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.

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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.

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It’s hard to find a gardener who doesn’t love checking out new seed varieties and anticipating the abundant and tasty harvest they promise. The photos and descriptions are tantalizing and the names intriguing. Who wouldn’t be curious about a pumpkin variety called ‘Abominable’, a pepper named ‘Frodo’, or a tomato tagged ‘Dancing with Smurfs’?  With so many seed varieties to select from, narrowing down the choices can be challenging. In January this year, a team of EDG volunteers had a lot of fun picking out varieties for our spring and summer crops.

How Seeds are Selected

Seed selection starts with a garden plan, taking into consideration the space available for each type of crop. Once decisions are made about which crops to plant and where to plant them, choosing the right varieties becomes the focus. The Demo Garden is the perfect place to try out some of those new and different seed options while continuing to plant those varieties that have proven to be reliable. Planting more than one variety of each crop makes it possible to directly compare them in terms of growth and productivity.

Time to maturity is important in determining which summer crop varieties to plant. The soil must be consistently warm (over 55 degrees) for the time specified in the variety description to produce a crop. The climate in the Indian Valley Organic Farm and Garden where the Edible Demo Garden is located provides a long enough growing time for most summer crops. However, varieties requiring more than 120 days to maturity may not achieve full production before the weather turns cool.

Seeds planted in the Edible Demo Garden must be organic certified. Organic seeds are from plants grown in compliance with federal standards which exclude the use of synthetic fertilizers, pesticides, and genetically modified technologies. Seed choices for the Demo Garden are often based on the descriptions provided by organic seed companies and it’s up to the volunteers to determine which varieties seem well suited for the garden conditions and promise the best taste.

Planting the Seeds

On February 27th, the new MMG training class got hand-on practice in seed starting. Seeds are planted in a starting soil mix in flats of cells with 2 or 3 seeds per cell. Supervised by EDG volunteers, the trainees planted 60 cells of cucumbers (‘Armenian’, ‘Crystal Apple’, ‘Jin Yang’ and ‘Early Fortune’) and 90 cells of sweet peppers (‘Pusztagold’ and ‘Bacskai Feher’), along with 30 cells of green onions and 72 cells of lettuce. The class will have the chance to take some of the cucumber and pepper starts home to plant in their own gardens where they can assess how well they grow in our different microclimates. The planted seeds are now germinating in the greenhouse.

Starting plants in the greenhouse gives them an advantage and allows better timing for optimum crop production. They are not ready for transplanting outside until they have developed at least one set of true leaves. The first set of leaves to appear are embryonic leaves called cotyledons. They look different from the plant’s typical foliage. True leaves are the more recognizable leaves that develop above the cotyledons. The time required for seedlings to be ready for transplanting varies. Beans can be ready in 3 to 4 weeks while peppers can take more than 8 weeks.

New Varieties in the Demo Garden

EDG volunteers look forward to growing the new seed varieties they have selected for the summer. The seeds have been ordered but not all have been planted. ‘Dancing with Smurfs’, an indigo-colored cherry tomato, along with ‘Altai Orange’ and ‘Woodstock’ are among the new tomato varieties. Two new melon varieties, ‘Sweet Freckles’ and ‘Farthest North Galia’ will be tried in the garden. The ‘Pusztagold’, and ‘Bacskai Feher’ peppers, now germinating in the greenhouse, are small, sweet Hungarian type peppers. Last summer’s pepper crop included an overabundance of hot peppers, so it’s sweet peppers in demand this year.

Starting with seeds is rewarding. There is the pleasure of choosing seeds from the many available varieties and the joy of nurturing them and watching them grow into tiny plants. It’s even better when the veggies and fruits turn out to be as yummy as the seed descriptions promise.

Click here for more information on planting from seeds.

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.

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.