Fruit Trees

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

Spring is here and plants in the Edible Demo Garden are beginning to bloom. Not all the blooming plants in the garden are edible crops – some are there for their flowers. The flowers add to the beauty of the garden, but they don’t just look pretty – they have important jobs to do. They attract pollinators, repel pests, provide a habitat for beneficial insects, and contribute to the biodiversity of the garden. It turns out that many flowering plants can be good companions for the edibles.

 

A variety of flowers are grown in the Edible Demo Garden. Some are perennials such as yarrow and lavender. Others are annuals that are grown from seed in the greenhouse and planted each year. These include zinnias, marigolds, and calendula. Then there are the flowering plants that self-seed and return on their own like the California poppies and the sunflowers. Sunflowers have been so successful in the Edible Demo Garden, that they sometimes show up where they are not wanted.

 

Favorite flowers for attracting pollinators

It’s easy to tell which flowers are popular with bees – just head for the buzzing sound. The California lilac (Ceanothus), planted in the garden several years ago, blooms early, ensuring that there will be bees around when the spring vegetable crops start blooming. Although it’s also a culinary herb, rosemary (Rosmarinus officinalis), is another bee magnet. It turns out that many of the culinary herbs and herbs for tea produce flowers that attract pollinators. Mexican tarragon (Tagetes lucida), Anise hyssop (Agastache foeniculum), Coneflower (Echinacea)and Chamomile (Matricaria recutita) all do double duty in the Edible Demo Garden. Nectar producing flowering plants, like the Cleveland sage (Salvia clevelandii) and California Fuschia (Epilobium canum) also attract hummingbirds and butterflies to help in the pollinating work.

 

Flowering plants that discourage pests

There is increasing scientific-based evidence that certain plants are effective in managing pests in an edible garden. They can confuse pests, luring them away from their favorite target and disrupting their feeding and egg-laying behaviors. Studies have suggested that plants with strong odors can discourage pests by masking the scent of the desired host plant. Marigolds (Tagetes) have long been a pest-repelling favorite of gardeners, but the supporting science is scant. However, there is research showing their effectiveness against parasitic nematodes and some flies affecting vegetable crops. In addition to their ability to attract pollinators, Nasturtiums (Tropaeolum majus), have been found to reduce squash bug damage when grown with zucchini. Their edible flowers make them especially welcome in the garden.

 

The importance of diversity in the garden

Mixing in some flowering plants with the edibles encourages beneficial insects that can keep pests in check. Members of the Asteraceae family, which includes yarrow, sunflowers, zinnias, calendula, and asters, support beneficial insects that dine on aphids. Flowering herbs provide nectar for parasitic wasps which help control caterpillar pests. Low -growing flowering plants such as thyme and oregano provide a sheltered habitat for ground-dwelling beneficials.

 

The right flowers in an edible garden are not just ornamental, they balance the garden. They help in creating a habitat that supports plant growth and production and reduces the need for pesticides and other pest-management strategies.

 

Click here for more information about plants that attract pollinators.

While the rains limited some of the garden work during January, it was the perfect time to assess the condition of the garden beds and plan for the spring and summer crops. Some of the beds are dedicated to perennials such as blueberries, raspberries, and rhubarb. Others have typically been used to grow herbs and spices like mint, tarragon, and horseradish. However, most of the beds are reserved for annuals and that’s where the planning comes in.

In addition to deciding what to plant and securing the seeds, it’s important to determine the best location for the plants. The main considerations are light, water, and soil. All the existing beds receive plenty of sunshine and have access to irrigation. Soil condition then becomes key in deciding where crops should be planted. A goal in using soil more effectively is to rotate
crops and avoid planting the same crop in the same place season after season.

Why is rotating crops important?
Rotating crops can help retain soil fertility and prevent the buildup of soil borne diseases and pests. Plants differ in micronutrient needs and susceptibility to soil pathogens. The problems that affect plants from one family, may not be an issue for plants from another family. Moving a particular crop, such as cucumbers, to a different planting location each season, can reduce the possibility of infection by diseases that target members of the cucurbit family.

Categories for crop rotation
There are different ways to divide crops into groups for crop rotation. One way is to split crops into categories based on the part harvested. Leafy crops, for example, would be planted together and moved to a new location each season followed by fruit crops, root crops, and legumes. Another method is to group crops as heavy or light feeders according to their nutrient needs. Moving heavy feeders to beds previously occupied by light feeders can make better use of soil nutrients. The most common grouping for crop rotation is according to botanical plant family. Tomatoes, eggplant, peppers, and potatoes are members of the Solanaceae family. Solanaceous crops share the same pests and are susceptible to some serious soil borne viruses.
Preferably tomatoes should not be planted in the same place more than once every four years allowing time for soil diseases to die out. Other plant families to be planted and moved together are the cucurbits (squash and cucumber), alliums (onions, leeks, and garlic), brassicas (broccoli, cauliflower, and cabbage) and legumes (peas and beans).

Difficulties in rotating crops
The ideal rotation plan would involve a three- or four-year cycle. This can work well in a garden large enough to be divided into quadrants. When space is restricted, the cycle may need to be shortened and the number of plant groups reduced. At the very least, home gardeners with limited space should avoid planting the same crop or crops from the same family year after year in the same part of the garden.

In the Edible Demo Garden, straw bales and grow bags are used to increase the available planting space. Because the straw bales are replaced each year and new soil is added to the grow bags, there is no need to rotate the crops planted in these spaces. The straw bales work well for the cucurbit family plants and this frees up garden space for plants from other families. The plans this year are to use the grow bags for tomatoes.
Want to visit the Edible Demo Garden? You’ll find volunteers on site most Tuesday and Friday mornings from 9-11 am. The garden is located within the Indian Valley Organic Farm and Garden on the College of Marin campus in Novato.
Click on this link for more tips about crop rotation.

Year around gardening in the Edible Demo Garden includes planning for crop rotation

Leafy greens can grow together and rotate as a group

Straw bales serve as new beds for squash plants in the Edible Demo Garden