Soil preparation, amendment/fertilization
Prepare soil thoroughly by plowing, tilling or spading before planting. Remove all weeds. Incorporate lime and organic matter such as well rotted manure or compost into the top 20-25 cm of soil before planting. Apply lime if soil is below pH 7, at a rate of 4.5 kg lime per 9 square meters. Prepare the soil before the trees arrive from the nursery if possible. Apricot does not usually develop many nutrient deficiencies. The level of N fertility has more influence on the growth, yield, and quality of apricots than any other single plant nutrient. Adequate supplies of N are necessary to optimize growth and development of newly planted trees.
Compost, animal manure and green manure can be worked into the soil to a depth of 1m, however, this should not be added directly to the tree planting hole at the time of planting, but in advance of planting so that rotting can occur and be completed prior to planting, otherwise root rot is likely. Organic sources of N, such as urea should be. Applied during winter and/or spring, to allow for timely decomposition and release of nutrients. If nitrogen is to be applied, it should be applied at the rate of 20-55 kg per hectare of actual nitrogen.
Many weeds compete strongly with new apricot trees and should be eliminated before tree planting.
Apricots are planted in solid blocks if self-fruitful, at spacing’s of up to 4 to 7 meters between trees and rows. If cross-pollination is required, pollinizers can be in equal numbers as the varieties they pollinate, if the pollinizer produces desirable fruit. If the pollinizer fruit is of poor quality, plant 1 pollinizer to every 9 main crop trees, spacing the pollinizers evenly in the orchard. The most effective design with pollinizers is on a 3 x 3 tree square, with 9 trees and the center tree is a pollinizer. Closer spacing’s may result in smaller trees, or if trees become too big they will shade each other out and fruit production will be reduced. Apricot trees that are well-watered and well-fertilized can grow up to 9 meters tall, but if allowed to grow vigorously to this size, few fruit will be produced. Apricot trees will develop at least a 5-meter diameter limb spread at maturity. Plant them far enough apart to avoid excessive competition. Orienting the tree rows north to south will improve light exposure to the fruit.
Shaping your young trees
Control size by pruning to approximately 5 meters or less so that trees only ‘fill’ the available space in the orchard between trees and rows when trees start producing. Apricots should be trained as ‘vase-shaped’ or ‘open center’ trees to get enough light into all parts of the canopy so that flower buds will form and best quality fruit will be produced. Generally, all new growth and interfering wood is removed each year once trees are full-size. Trees have limited resources for growth and reproduction; if all resources are used for vegetative growth to get big trees, no resources will be available to produce fruit. Big trees do not produce more fruit.
Nursery trees and planting
When the fruit trees arrive from the nursery, open the bundles immediately to inspect for damage and check general condition of the trees. Make sure the roots do not dry out; most fruit trees will be ‘bare root’, that is without soil around the roots when they come from the nursery. “Heel in” the trees if you are not ready to plant them. “Heeling in” means to dig a shallow trench in which tree roots or a bundle of trees can be covered with moist soil to protect them until planting. Plant when the ground is not frozen, but before trees start to ‘leaf out’ in the winter, to allow for root development before spring growth. During the first two or three years, the objective is to develop a sturdy tree of good size. Little or no training is given apricot trees, other than topping them at planting to assure development of low heads. It is advisable to allow the tree to grow its branches at a minimum height of 2/3-1 m to prevent fruit from touching the soil when on low limbs.
Prepare the planting hole
Dig a hole only as large as necessary to accommodate the root system. Trees should be planted with their top major roots even with the soil line. Prune any damaged roots back beyond the damaged area. If container-grown trees have a tap root curled in the bottom of a container, cut this root off at the point where it begins to curl. Separate and trim the roots of container trees that may be root-bound. If trees are bare-root, cut off any roots that are broken or kinked. Save the soil from the hole to use as backfill. If the hole is deeper than the measurement, prior to placing the tree in the hole, backfill with enough soil to hold the tree slightly higher than the measurement. Firmly press the soil before setting the tree on it. Be sure the root ball or container soil rests on solid ground to prevent settling. Do not add any other soil amendments to the hole, such as fertilizer or compost.
Position the tree
Carefully remove the tree from the container, supporting the root ball. Place the tree in the hole at the same depth it was growing previously. If holes are dug too deeply, and loose soil is placed at the bottom, trees may settle after watering. Trees set too deeply may die. Container trees should have the top of the soil ball flush with the top of the hole. Bare-rooted trees should have soil placed underneath them in a manner to allow the spreading of the roots in a natural position with no bending or crimping. Cut any circled or kinked roots and score the outsides of the root ball if it is compacted. Loose roots should be positioned facing down in the hole. The graft union should be no less than 5 to 10 cm above the soil surface when the roots are completely covered with soil.
Fill the hole
Remove any rocks, grass or debris from the dug-up soil. Break up clods. Back-fill with the same soil that was removed from the hole. Never back-fill with an amended soil mix of a lighter texture. Such a practice will create drainage problems and cause tree roots to suffocate during periods of excessive moisture. Firm the soil around the lower roots by hand. Continue filling and firming several cm at a time. Soil should be firmly, but not tightly, packed. Pull out all weeds surrounding the planting hole. Before completion of back-filling, add water to settle the soil and eliminate air pockets around the roots. After watering, fill the hole to completion and, if necessary, construct a basin (ridges of soil around the complete circumference of the tree) to hold water during subsequent irrigations. With trickle irrigation, this practice may not be necessary. Basins are not needed during excessive rains or if flood irrigation can be effective used at regular intervals after planting.
After the tree is planted, water well. Check the original soil line one last time. If the tree does settle, now is the time to move it back to the correct position with the soil level against trunk at the same level that it was in the container. As a general rule, after the soil has settled, the uppermost large root should be just below the soil surface. Construct a basin for watering the newly planted tree, making sure that water drains away from the trunk. The basin should be slightly wider than the planting hole so that water can be applied to the entire root area and just beyond. Most of the root volume occupies a rather limited area, particularly through the first growing season, so frequent watering may be needed until the roots become established. Fill the basin once or twice a week in hot weather, less often when it is cool or rainy. Water must soak into the root ball of container-grown or bare-root trees since they cannot obtain water from the surrounding soil until their roots grow into it. Level the basin in winter so that the tree does not stand in accumulated rainwater. The ground within about 1 m of the tree trunk should be kept free of grass, weeds, or other vegetation that can compete with the tree for water and nutrients. A layer of mulch 7.5 to 15 cm thick, such as wood chips or grass cuttings helps control weeds and conserve moisture. Mulch should be kept several cm away from the trunk to minimize the occurrence of crown rot and eliminate hiding places for insect pests.
Stake if needed
Unless the tree bends over, it will not need support from staking. If stakes are needed, place them on opposite sides of the tree, perpendicular to the direction of the prevailing wind. Stakes should be positioned outside the root ball area, but no further than the tree ties can reach. Drive stakes into soil so that the top of the stakes should be a couple of inches below the lowest main branch. Place tree ties about 15 cm above the spot where the tree bends which will be about 2/3 to ½ of the way up the tree. In order to prevent ties from rubbing the tree’s bark use rubber loops cut from automotive tires between the ties and the tree. Loop ties around the tree and attach one to each stake. Ties should be loose, so that the tree can sway, and the trunk can grow stronger.
Sunburn protection at planting
The bark of newly-planted trees is very easily damaged by too much sun; when injured, the bark is easily infested by borer insects. Protect the bark of the tree from sunburn immediately after planting by painting with white interior latex paint diluted to half strength with water. Apply the paint mixture from the soil surface up the entire trunk, including the dormant buds. Pruning newly-planted trees.
General rules for pruning apricot trees.
- Prune trees at planting time to balance the tops with the roots.
- Prune young trees very lightly.
- Prune mature trees more heavily, especially if they’ve shown little growth. Tree canopy should be kept open with considerable thinning-out in order to induce annual formation of fruit-bearing wood. Apricot fruit is borne on short spurs that are short lived.
- Prune when all danger from fall or early winter freeze has passed, but before full bloom in spring. This reduces the risk of disease and injury , however, apricots bloom very early; consequently, all or most of the flowers or young fruits are frequently killed by frost. Delaying pruning until after bloom may be advisable with apricots grown in an area that gets late frost frequently.
- Prune less heavily if there is a light or no crop at all.
- Prune the top portion of the tree more heavily than the lower portion as the top is where most vegetative growth occurs.
- Thin out more shoots toward the end of a well-pruned branch in a mature tree. This will increase fruit size and quality on the remaining shoots.Pruning too early in the dormant season can lead to the following problems:
- Increased incidence of Cytospora canker, which enters the tree through pruning wounds. Pruning close to bud break when the tree starts active growth leads to rapid healing of pruning wounds.
- increased internal damage.
- increased sunscald of the bark.