Orchard Calendar: December

Lowering the height of fruit trees

Pruning: lower the heights of fruit trees. Lower the heights of fruit trees if you want to do most of your tree management without a ladder. Lowering the height of your fruit tree to a pruned height of 6 1/2 feet will allow you to prune, spray and harvest while standing on the ground. Most full sized fruit trees can be kept to this height through judicious pruning methods. Apples should be grown on a semi-dwarfing rootstock.

 Pruning: begin pruning for production. Each type of fruit tree is pruned differently. You must know where your fruit is being produced on the tree that you are pruning.

4 to 8 inches of mulch on the orchard floor

Mulch. Use organic mulch in the Orchard or around fruit trees. This is not the same as bark mulch which is inferior to wood mulch. Wood mulch can be kept to a depth of 4 to 8 inches around fruit trees. On younger trees, keep wood mulch 12 inches away from the trunks until they are 6 to 8 years old. Green waste from pruned and chipped ornamental trees makes an excellent mulch. Avoid using trees such as Mesquite with their large thorns and palm trees which decompose very slowly. Organic mulches such as wood mulch return nutrients to the soil, increase microbial activity, retain moisture around the plant roots, reduce weed problems and help keep the soil cool.

Fruit trees at Orchard irrigated by modified flooding: bubbler and basin

Asparagus turning brown in the winter

Irrigate fruit trees deeply every 10 days. After leaf drop, irrigations can be applied every 10 days to two weeks if you have a surface mulch applied to the soil. Sandy soils may require irrigations weekly to every 10 days. Heavier soils may require an irrigation every two weeks.

Applying compost to the raised beds

Cut down asparagus. Asparagus growth is cut to the soil surface when it turns yellow or brown. If this does not happen by the end of the month, cut the asparagus down to the soil surface.

Compost planting beds to be rototilled. Those beds which have not been planted should be prepped for next season. Use a high grade of compost to improve the soil to a depth of 12 inches. Incorporate a high phosphorus fertilizer in the planting row or in the backfill when planting transplants.

Borer control. This time of year concentrate on removing borer damage from fruit trees. Look for borer damage on the upper surfaces of limbs, particularly of peach, nectarine and an apricot. Using a sharp, sterilized knife remove the damaged wood from these areas. Be sure to cut all the way down to fresh wood when removing damaged wood. Let the tree heal by itself. Do not apply pruning paint but you could apply whitewash.

Whitewash applied to fruit trees

Dormant oil application. Dormant oil is an insecticide made from petroleum products used in organic production. The oil itself is not toxic but spraying it on the limbs and trunk of fruit trees helps to suffocate overwintering, usually soft bodied, insects that are pests of tree fruits. Usually to applications are made during the winter months.

Weed control. Weeds that are living close to your fruit trees provide homes for overwintering insects. Once your trees begin growing in the spring, these insects move from weeds to your trees. Keep in areas near your fruit trees without weeds.

Borere control with a sharp knife

Renew whitewash on fruit trees if needed. Whitewash provides a light colored covering to the outside of the bark of the tree and its limbs. It is particularly important in reducing sun damage to fruit trees due to our high light intensities. Whitewash can be made by diluting white latex paint with an equal amount of water or more. Dilute the white latex paint so that it will color exposed areas of the tree white and reduce sunburn. Reducing the sunburn will reduce the damage from borers.

Pull wood mulch away from the trunks of young trees about a foot. Wood mulch that gathers around the trunks of small trees can damage them.

Limb spreaders on a young apple tree

Remove any stakes from trees planted early in the year. Fruit trees that are planted correctly and are not overgrown in their containers will need staking for only one season. If your trees have not become established after one season, there is a problem.

Remove limb spreaders that were used earlier in the year. Limbs spreaders are used to increase a limbs angle of attachment to the trunk of the tree. Ideally, this should be a 45° angle. Limbs spreaders can be applied to the tree now but there is less danger of breakage in larger limbs when the sap is flowing in March. Ideally they should be applied when the limbs are one to two years old.