Planting & Spacing

No matter what season, there is always weeding to be done in the Edible Demo Garden. Weeds seem to pop up everywhere – in and between the raised beds, in containers, and even in the straw bales. They are the uninvited guests among the cultivated organic fruits and vegetables.

What is a Weed?

The definition of a weed is tricky – more a value judgement rather than a plant category. Weed is a label given to a plant that is undesirable where it is growing. Any type of plant can be considered a weed if it turns up as an unwanted volunteer and competes with crops and landscape plants for water and nutrients or harbors viruses that can infect other plants.

Some plants such as purslane, which is considered by most to be a nasty weed, is also cultivated as an edible. Amaranth, a beautiful plant that has long been used for food by indigenous cultures, has a bad habit of showing up where it isn’t wanted. Even some popular native plants and wildflowers can get out of control and be considered “weedy”.

Although weeds are often described as invasive, the UC Integrated Pest Management Program considers invasive plants to be “a distinct group of weeds that occur in natural habitats”. They differ from common garden and agricultural weeds in that they are non-native and infest ecosystems causing damage to natural areas.

Annual vs Perennial Weeds

Annual weeds appear seasonally in summer or winter and are spread only by seeds. This makes a difference in how they can be controlled. The strategy is to get them out before they can go to seed. Common annual weeds include cheeseweed, crabgrass, purslane, and spurge.

Perennial weeds all have underground parts that enable them to spread through root systems as well as through seeds. These are the more stubborn weeds such as bermudagrass, field bindweed, dandelion, and yellow nutsedge. It takes some digging to completely remove perennial weeds.

Weed Management in the Edible Demo Garden

Only non-chemical methods for weed management can be used in the organic garden. Physically suppressing and removing weeds is a never-ending task for garden volunteers. It takes repeated efforts to reduce weed populations. Sheet composting and mulch are applied to suppress weeds between the garden beds. A weed-whacker has proven to be a handy tool for getting rid of annual weeds before they produce seeds. However, hand-pulling and digging remain the best methods for eliminating the most persistent of the pesky weeds. Some volunteers even claim to experience some “Zen” moments while weeding.

Read more about controlling weeds by clicking here.

Additional information can be found on the UC IPM website by clicking here.

Two years ago, volunteers planted six bare-root fruit trees in the Edible Demo Garden. Although some did not survive and were replaced, there is now a row of small fruit trees that are beginning to produce. The trees in this little orchard do not demand as much attention as the annual edible crops, but they have their own seasonal care requirements.  In addition to regular irrigation and fertilization, fruit trees need pruning, fruit thinning, and disease management.

Why prune fruit trees?

All fruit trees require pruning for optimum vigor and fruit production. Pruning is also a way to control tree size, making care and harvesting easier. The first pruning of the fruit trees in the Edible Demo Garden was done at the time of planting. Following recommendations for keeping the trees small, a hard heading cut was made on the new bare root trees to remove approximately two-thirds of the main trunk to about knee height. In the following years, both winter and summer pruning have helped to shape the trees and maintain their health. Pruning in the winter when a tree is dormant helps to invigorate it and encourage new growth. Summer pruning is done to remove excess growth and control the dimensions and shape of the tree. Ideally, pruning should strive for a balance between the growth of new wood and the removal of old wood. The goal is also to allow sunlight to reach the lower limbs to enhance fruit production.

Pruning to remove any damaged, diseased, dying, or dead limbs is always important. Rootstock suckers and sprouts emerging below the graft section of the tree need to be pruned off. Shoots growing from the rootstock deplete energy from the scion or grafted part of the tree where the fruit is formed. Likewise, water sprouts are suckers that grow upright in the crown of the tree, and they also should be removed to direct the tree’s energy to fruit-producing branches.

Why should fruit be thinned?

Removal of flowers or fruit early in the spring increases the size of the remaining fruit by improving the leaf-to-fruit ratio. A ratio of 40-75 leaves per fruit is required to produce good-sized fruit in standard apple, peach, and nectarine cultivars. Plums and apricots need a leaf-to-fruit ratio of 30 to 50 leaves per fruit. The earlier that fruit are thinned, and the leaf-to-fruit ratio is increased, the larger the fruit will be at harvest and the greater the effect on next year’s bloom. Rather than count leaves, it’s more practical to thin most fruits to about 4-8 inches apart along a branch or to leave only one fruit per spur. Save the largest fruit and adjust the number of fruits to size of the limbs. Not only will the fruit be smaller on trees that are not thinned, but excess fruit can break branches and weaken the tree.

What common diseases have affected the trees in the Edible Demo Garden?

Sadly, organic gardens are not immune to the bacterial and fungal diseases that frequently affect fruit trees. Fire blight is a bacterial infection that attacks pome fruits like pear, apple, and quince trees. Young blossoms, shoots, and fruit shrivel and blacken, causing branches to appear burned. The disease can spread rapidly so it’s important to cut diseased branches back into about 12 inches of healthy wood to remove all the infected tissue. The bacteria can be transmitted by pruning tools, so they need to be sterilized before making each cut. In the Edible Demo Garden, a young Bartlett pear tree was infected by fire blight this year.

A frequent problem for stone fruits such as apricots, peaches, and plums, is leaf curl. This is caused by a fungal infection that attacks the leaves, shoots, and fruit, causing leaves to become thickened and pucker and fruit to drop. The fungus overwinters and becomes active in the spring when it is spread by splashing rainfall. The leaf curl fungus has infected an Asian plum tree in the Edible Demo Garden.

Copper-based fungicides can be used for the prevention of both fire blight and leaf curl; however, the timing of the applications is important. Treatment needs to be initiated early before any signs of disease are visible. Because copper is a naturally occurring mineral, it is acceptable for use in organic agriculture.

Click here for more information on the care of fruit trees

The soil in the Edible Demo Garden gets a lot of attention. Compost and organic amendments are added regularly. Moisture levels are monitored, and rainwater is supplemented with drip irrigation and hand watering. Mulch and cover crops are used to protect the soil and tilling is kept at a minimum. The goal of these efforts is to maintain the structure and composition of the soil so that the growing plants have access to the air, water, and nourishment they need.

However, soil can look and feel healthy, and still be lacking nutrients essential for optimum plant growth. Plants suffering from malnutrition look unhealthy and show symptoms of deficiency. Growth may be stunted, leaves may be chlorotic (yellowed) or distorted, and shoots appear short and thin. Too little or too much of any one nutrient can cause problems. The best way to check for a lack of nutrients in the soil is to test a sample.

How are the nutrient components of soil tested?

Inexpensive do-it-yourself soil test kits are readily available in garden centers, and they can be a convenient way to determine soil pH and levels of the primary macronutrients: nitrogen, phosphorus, and potassium. More comprehensive tests which cover secondary macronutrients and micronutrients, can be performed by commercial soil testing laboratories.

Any soil test should start with a carefully collected soil sample. Use a stainless-steel trowel or shovel to obtain a sample at least six to eight inches below the soil surface. Avoid wet soil, if possible, the sample needs to be dry for testing. Taking samples from several places in a garden bed and mixing them can be useful in measuring overall chemical properties. However, samples from different garden areas (vegetable, perennial, lawn, etc.) should be kept separate. Soil testing laboratories generally provide specific instructions on sample collection.

Why does soil pH matter?

Nutritional elements in the soil need to be in a soluble chemical form to be absorbed by plant roots. There must be sufficient moisture in the soil to allow the roots to take up and transport the nutrients. The temperature of the soil also needs to fall within a certain range for uptake to occur. Finally, the solubility of the nutritional elements and the activity of the microorganisms responsible for the chemical transformation of nutrients are directly influenced by soil pH.  An essential nutrient can be present in the soil, but not in a form the plant can use. Each nutrient has an ideal pH range for plant availability. At pH levels that are too acidic or alkaline, some nutrients can become insoluble and not accessible to plant roots. Phosphorus, calcium, and magnesium are elements that become less accessible as soil increases in acidity, while the availability of iron, zinc, and manganese is reduced in more alkaline soils. The ideal pH for most plants is between 5.5 and 7.5.

What nutrients are commonly lacking in soil?

The nutrient most commonly lacking in garden soils is nitrogen. Most plants absorb nitrogen in the form of ammonium or nitrate. These forms readily dissolve in water and leach away. Excessive irrigation and heavy rains can lead to nitrogen deficiency in the soil. Phosphorus, potassium, calcium, magnesium, and sulfur are the other macronutrients that may be deficient, depending on drainage and pH levels. A lack of iron, zinc, or manganese, all considered micronutrients, results in interveinal chlorosis, a condition in which the leaf veins remain green while the rest of the leaf turns yellow. The uptake of these micronutrients is also affected by pH.

For more information on assessing soil health, click here.

For hands-on practice in soil testing come to the workshop co-sponsored by the Edible Demo Garden and the Edibles Guild. Click here to register.

The rain in February flooded the areas around the garden beds in the Edible Demo Garden. Volunteers were busy digging trenches to redirect the water away from the planted areas and salvaging any crops that were still productive. The wind also created havoc, blowing over compost bins, scattering planting containers, and overturning a picnic table. Once the damage was mitigated, there was little that could be done in the garden itself until the water drained and the soil began to dry. Attempting to work in soggy soil can create future problems due to soil compaction.

However, the Edible Demo Garden volunteers are not a group to remain idle, especially when it’s time to start seedlings for the spring and summer garden. The organic seeds for the chosen crops had arrived and they needed to be planted in the proper soil mixture and placed in the greenhouse to germinate. So, on a rare dry day, an enthusiastic group of volunteers met to make soil for growing seedlings.

What soil is best for starting seeds?

While some plants such as carrots, grow better when they are directly seeded into the garden, many others benefit from earlier starts in more protected conditions and are transplanted later into the garden. In the Edible Demo Garden, any soil used to start plants from seeds must be organic, containing no synthetic materials. Due to the amount of soil needed, it’s much more economical to make the seedling mix rather than purchase a ready-made organic mix. There are many recipes for seeding mixes, but most important is that they are formulated to hold air and moisture and are free of harmful bacteria. There are two soil mix recipes developed for the Indian Valley Organic Farm and Garden and these are also used in the Edible Demo Garden. Labeled “Breakfast Mix” and “Lunch Mix”, they are made by hand and shovel in large quantities. Screen tables set over plastic tarps are used for the sifting.

Breakfast Mix

Breakfast mix is used for starting seeds in trays or flats. It is made by sifting together the following materials:

• 4 wheelbarrows Lunch Mix (20 cubic ft., already sifted)
• 1 bag Vermiculite (4 cubic ft.) (medium or fine)
• 1 bag Peat Moss (4 cubic ft.)

Lunch Mix

Lunch mix is used for potting up seedlings prior to transplanting or for bigger plants that will remain in 1–3-gallon containers for several months or more. The recipe for lunch mix is as follows. All the ingredients are mixed thoroughly and sifted together.

• 6 wheelbarrows sifted compost
• 1 bag Peat Moss (4 cubic ft.) 
• 1 bag Vermiculite (4 cubic ft.) (medium or fine)
• 1 bag Perlite (4 cubic ft.) (medium or fine)
• 10 lbs or 6 qt Azomite (micronized)
• 5 lbs or 5 qt Feather Meal (fine)
• 2.5 lbs or 2 qt Kelp Meal (fine)

What is the purpose of the ingredients in a seedling mix?

Any mix must meet the needs of plant roots for air, water, nutrients, and support.

• Compost – adds structure, provides nutrients, and contains beneficial microbes
• Peat moss – retains moisture (coconut coir is considered a sustainable alternative)
• Vermiculite – mined mineral, increases soil porosity and adds calcium and magnesium
• Perlite – light, volcanic rock, helps to aerate by increasing pore space
• Azomite – adds trace minerals
• Feather meal – releases nitrogen
• Kelp meal – adds nitrogen, potassium, and phosphorus

Ready to plant

Once the “breakfast mix’ was made, it was used to fill seeding trays and planting could begin. A light topping of vermiculite was added to each cell to maintain the right moisture level.

Click on the following for more information on soil mixes and starting plants from seed: 

Sowing seeds for fun, flavor, and a successful harvest

Build healthy soil

In December EDG volunteers planted winter garden edibles including carrots, fennel, cabbage, kale, and – artichokes. While artichokes may not be on every gardener’s cool season vegetable list, they are fun to grow, and December is the right time to plant them for an early spring crop. Since almost all artichokes sold commercially are grown in California, it was designated the official state vegetable in 2013.

What is an artichoke?

Artichokes are large plants in the sunflower family (Asteraceae). The edible parts are the large flower buds that form on the tops of tall stalks. The buds are typically green, but some varieties are violet-tinged. Buds that are not harvested for cooking and eating will open into attractive purple thistlelike flowers.

Although some may consider artichokes exotic and too much trouble to eat, they have been enjoyed since Roman times. Italian immigrants brought artichokes to Monterrey County where they grew well in the Mediterranean like climate. When artichokes first became popular in the US there was a problem meeting the demand and there are stories of a Mafia attempt to corner the market. Fortunately, we can now have all the artichokes we want to eat when they are in season.

What artichoke varieties grow well in Marin?

Artichoke plants need exposure to temperatures below 50 degrees to form buds, but they are easily damaged by frost and freezing temperatures. The plants also suffer in hot dry summers. Artichoke varieties differ in their tolerance for cold and heat but they like the coastal Bay Area climate. The standard variety is ‘Green Globe’, the variety most often found in the supermarket. The two varieties planted in the Edible Demo Garden are ‘Imperial Star’ and ‘Colorado Star’. These varieties mature faster and require fewer chill hours than ‘Green Globe’.

Are Artichokes Annuals or Perennials?

In California artichokes are commonly grown as short-lived perennials producing both spring and fall crops. After the spring harvest they are cut back to the ground and kept dry to encourage summer dormancy after which they are regrown in the fall for another crop. However, early maturing varieties like ‘Imperial Star’ and ‘Colorado Star’ also work well as annuals when planted in late fall. In the Edible Demo Garden, the two new varieties replaced older plants that had aged past their prime and suffered some gopher damage.

How to Grow and Harvest Artichokes

The artichokes planted in the Edible Demo Garden were grown from seed in the Indian Valley Organic Farm and Garden greenhouse. Seedlings are ready to plant in 8 to 12 weeks. The plants require a sunny location with fertile, well-drained soil. They need consistent watering and monthly doses of high nitrogen fertilizer. They also require some space since the plants are typically 3-4 feet wide and tall.

The buds on the artichoke plant are ready to harvest just as the lowest bracts begin to open. Once a bud opens more fully, the tenderness and flavor diminish.  Harvesting the top bud stimulates the lower buds to develop. Buds should be harvested by cutting the stem about 2 inches below the bud.

For more information on growing artichokes, click here.

After the fall harvest was over, it was time to clean up and replenish the soil in the Edible Demo Garden. Healthy soil is fundamental to the success of the next season’s crops. Even in beds that are temporarily fallow, the soil needs to be nurtured and protected. In November, volunteers were busy with three major soil-boosting activities - spreading compost, adding mulch, and planting cover crops.

Why add compost?

The value of compost cannot be overestimated. Most edible crops are heavy feeders and leave the soil depleted of nitrogen and other essential nutrients after they are harvested. Adding a layer of compost to the soil is an earth-friendly way to help restore those nutrients and support good soil structure. Since compost is decomposing organic matter, it needs time to make the nutrients available to plants. In the Edible Demo Garden, compost is applied to all the garden beds prior to planting the next season’s crop.

What is the purpose of mulch?

Mulch is any material placed on the soil to protect it by conserving moisture, moderating temperature, and preventing erosion. Mulch is also used to suppress weeds. Mulch material can be organic or inorganic. Only recycled organic mulch is used in the Edible Demo Garden. Unlike compost, mulch is not intended to amend the soil and the materials used are generally coarser and break down slowly.

In late fall, Edible Demo Garden volunteers take apart the straw bales used to grow warm season vegetables. The used straw becomes recycled mulch. Initially, the straw was considered suitable as compost material, however, subsequent testing found it to be low in nitrogen. Although much nitrogen was added to the bales during the growing season, most of it was either taken up by the plants or washed out by watering and rain.

Why plant cover crops?

Cover crops, sometimes referred to as “green manure”, are another excellent way to protect and improve soil. Cover crops are divided into two main categories: legumes, such as clover and fava beans, and non-legumes, like rye and buckwheat. Legumes have the added benefit of fixing nitrogen by taking it from the air and converting it into a form to be used by plants. Cover crops are turned over when they start to flower and allowed to decompose prior to spring planting.

For several years Edible Demo Garden volunteers have been cultivating a large garden area known as “the back 40”. Planting a cover crop of fava beans in the fall is one of the strategies for improving the poor soil in that area. Before the fava beans could be planted in November, some light tilling of the soil was necessary to improve the penetration and decomposition of the four wheelbarrows full of compost spread by the volunteers. Prior to planting, the bean seeds were soaked in an inoculant containing rhizobacteria to maximize their nitrogen fixation effects.

Paying careful attention to spacing and depth requirements, 150 inoculated fava bean seeds were planted in the back 40 by the volunteers. Some watering will be necessary until the rains begin, but a good crop of green manure should be available to nourish the soil in the spring.

For more information on building healthy soil, click here.