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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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.

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.