Mario Viveros

UCCE Farm Advisor, Kern County

Deciduous Tree Fruits and Nuts

February 14, 2002

Almond Tree Planting

The success of an almond orchard begins at the time planting. There are few principles but many details. A detail may not be that important at the time of planting but it may be critical during the orchard's mature phase. In the following paragraphs, we will consider important details when planting an almond orchard.

Soil. We have made the statement that almonds have done the best in deep, well-drained soil that is reasonably fertile and free of harmful salts. This statement can still be true, however, with the use of low volume irrigation systems an orchard can perform well in shallow soils. High quality water and soil amendments have allowed growers to reclaim saline-alkali soils. In the past these soils were classified marginal and not suitable for almonds, however, with new technologies and excellent management these soils have became quite productive.

Fumigation. It is done to reduce nematodes in the soil. Ideally, if nematodes are present you want to reduce their population up to 99 percent for up to two years. This will allow the tree time to develop a healthy root system that can ultimately withstand or tolerate some nematode damage. The decision to fumigate should be based on the presence of nematodes, crop history and rootstocks. In Kern County, we are mainly concerned with the root knot nematodes. However, we also have the lesion and ring nematodes which can also be a problem. Nematode damage thresholds are not well established for almonds. As a general rule, if soil analysis identifies root knot nematodes, ring nematode, or damaging species of root lesion nematodes on a site where almonds have been grown, fumigation is recommended before the site is re-planted to almonds. We must be aware that a resistant rootstock may not protect a young trees when planted in a heavily root knot nematode infested soil.

Both the Nemaguard and peach/almond hybrids are resistant to root knot nematodes but they are susceptible to root lesion and ring nematodes. In Kern County we don't use Lovell because it is susceptible to root knot nematode.

Time of Planting. Early plantings have been more successful than late plantings. January-February plantings are better than March plantings. When trees are planted in January-February, ambient temperatures are low which prevents leaf buds from growing. This gives the roots time to callus and regenerate new roots before leaf buds begin to grow.

Root Pruning. The root system of trees from the nursery will contain some large roots and few small roots. Their length in most cases will be such that they can be handled at planting time. However, the normal tendency is to prune them back to such a length that it will fit into the planting hole. This excessive root pruning practice will reduce the amount of food stored in the root system. Therefore, a minimum amount of pruning is recommended at the time of planting. The only roots that should be pruned are those that have been damaged. They should be cut back at a sound place.

Root Disinfection. An operation that should be practiced in planting fruit and nut trees. This will help in the prevention of crown gall which is a tumor-like disease that affects roots and the crown of trees. This disease not only decreases tree vigor but also opens the door to wood-rotting fungi. Once the hardwood is rotten at the crown and roots, the tree can be blown over by winds in winter-spring.
The roots can be protected by spraying the roots with a biocontrol agent. Galltrol® is one that is commercially available in the market. Please follow directions on the label.

Size of the Hole. The hole should be just large enough to receive the roots without bending or crowding them. If a soil auger is used, it should be 24-inches in diameter and the sides of the hole should be broken down to eliminate the auger's glazing effect. Compost or manure should never be placed at the bottom of the hole. It can create problems for the tree.

Depth of Planting. Trees should be planted with the bud union above the soil line. The safest rule under ordinary circumstances is to plant the tree at the same depth it grew in the nursery row. The reason being that the peach portion (rootstock) of the tree is more tolerant to Phytophthora species than the almond portion (sion). Also, to prevent diseases caused by Phytophthora species, trees should be established on raised berms. This has worked well in orchards which have a micro-sprinkler or drip irrigation system but it has not worked well in flood irrigated orchards.
Soil-root Contact. Direct contact between roots and soil is an essential part of a successfully planted tree. To accomplish good soil-root contact, the worker must get down on his knees and firm the soil under and around the roots with his fingers. You should not permit the worker to use his shoes to firm the soil around the roots. This can injure the roots and trunk. Remember, injuries can lead to crown gall infections. Once the soil has been packed around the roots, set the soil with water to insure a good soil-root contact and eliminate air pockets.
Soil Moisture. The field should be dried or contain seed bed moisture conditions at the time of planting. Once the trees are planted special effort should be made to insure good soil moisture around the root zone.

Tree Orientation. Trees are usually planted with the bud growing into the wind. There has been no major problems with this practice, however, problems are created when we leaned trees too much into the prevailing winds. In fact, there have been trees leaned at 40 degrees. When trees are leaned this much, the trunk develops a curvature at the base and shoots develop only on the southeast side of the turnks. This creates a lopsided tree that is difficult to balance at pruning time. To prevent this problem, trees should be leaned only 10 degrees.

Fertilization. Fertilization at planting time is not recommended since the tree contains enough nutrients for root and initial shoot growth. Nitrogen fertilization should be delayed until the shoots are about 4 to 6 inches in length. At this time, four ounces of commercial nitrogen fertilizer per tree should be placed 18 inches away from the trunk. This practice should be repeated two or three times during the growing season.

Prevent Root Dehydration. This is one of the most important points in tree planting. Special procedures must be in place to prevent moisture loss from roots. This is especially true when planting the peach-almond hybrid rootstock. The roots should always be kept moist during the planting operation. We should avoid the practice of distributing trees by the planting hole, then, come back and plant the tree an hour later. This practice may expose roots to dehydration which in turn may lead to poor tree growth.