Young sapling trees transplant easily when dormant (before they leaf out) in early spring. A good size is about 6 to 8 feet tall. They may be moved bare-rooted to a prepared hole, then carefully set at the level they were growing or slightly higher.
The new theory for planting trees is to give them a wide area of loosened soil so the roots can spread out easily. The prepared soil should be several times wider than the tree crown. The reason is that most of the new tree roots spread out sideways and develop in the top 4-24 inches of soil. The roots will go where the soil is loose and soft. If the soil is hard, they will not expand but will stay close to the root ball. The planting hole is dug to the depth of the root ball, and it should be set on firm soil.
The old theory was to dig a hole 6 inches wider and deeper than the root ball; field tests, however, showed this was not the best way. In heavy soil the hole became almost a bathtub, which the tree roots grew out of very slowly. In some places the hole held enough water that the roots drowned and died. Another old custom that did not stand up to scientific scrutiny was the addition of peat moss and other additives to the backfill soil. Field tests showed that trees planted in decent soil actually grew longer roots if no additives were used. Just plain soft soil encouraged the best root growth for new trees. If the soil is low in organic material, though, some compost would be beneficial.
Trees that transplant best are those with many fibrous roots, which are the thin small feeding roots, normally near the surface. A good root ball has many of these. Some species of trees withstand the shock of transplanting better than others and may be moved during spring or fall. Tap-rooted trees, such as oaks, have long, fleshy roots, with very fibrous feeding roots near the top. They are hard to move and should be transplanted only in the spring.
Trees should be dug before the buds break, not when they are in full leaf. The most sensitive time is just after the leaves or needles first expand, when the loss rate will be high. Carefully dug, well-watered trees, however, may be moved almost anytime except late spring and early summer. Trees in nurseries are actually dug when they are dormant and then put in pots or tied in burlap. These can be planted at any time. This is also true of container stock which is grown from the beginning in big pots.
Balled and Burlapped Trees
When planting balled and burlapped specimens, called B&B in the trade, first put the whole root ball in the hole. Then cut all the string holding the burlap together, especially the cord wrapped around the trunk at the top of the root ball. Carefully roll back the burlap, removing any nails holding it together, and tuck in under. Then add topsoil in layers and stamp in each layer to avoid air pockets.
Check the burlap! If it is the old-fashioned brown kind, it may be tucked underneath the plant and will decay in about six weeks. If it is the treated green burlap, it will take about eighteen months to decay and should be removed or slashed. If it is plastic that looks like burlap, it must be removed from the plant and the hole. It is amazing how many professional gardeners leave the string and often the plastic wrapping on, which kills the tree in a few years.
It is easier to remove the burlap after the plant has been lowered into the hole. When the burlap is removed before planting, the root ball often cracks. Cracked root balls portend a poor take and often death. If the burlap is left in the hole, it must be completely buried. Not one bit of it can remain above the soil level, because it will act as a wick and draw water out of the root area.
Container-grown trees present special problems. The planting mix in containers is usually not soil, but wood mulch and chips with additives. Container plants are constantly fed with liquid fertilizer to make them grow faster and are watered very often. It takes a long while for them to adjust, longer than for bare-root specimens moved from another part of the garden.
The roots in containers are often thick and may wrap around inside the pot. After ten or twenty years, these encircling roots with prove fatal and strangle the maturing tree. The solution is to check the root ball before planting. If encircling roots are seen around the edges, make several slices, up and down, all around the outside of the ball of earth, an inch or two deep.
The purpose of these cuts is to expose fresh-cut root edges to the new soil. Clean-cut edges are the point at which new roots are made. Use own your best judgment as to how deep to cut so as to create fresh-cut edges yet not damage the main part of the root system.
If the roots are very thick in the pot, such side slicing is recommended. Slicing also helps at the bottom of the root ball, which will be flat from growing in the container; slice it diagonally twice to make an X. All container stock makes new roots faster if the edges are slashed or loosened.
Container stock has another problem. If the plant has been heavily fertilized in the nursery, it may suffer from fertilizer starvation after it is planted. The leaves will begin to pale and may turn yellow. The solution is to gradually wean the plant from its rich diet by giving it half strength liquid fertilizer when it begins to pale. Do not fertilize after midsummer — just hope for the best. It can take a year or two for new roots to form and adapt to their new soil. It is not easy to diagnose fertilizer starvation because yellowing leaves can be caused by so many conditions, such as overwatering, drought, soil problems, too much sun, and too little nitrogen.
After planting, all trees should be well soaked with water, which should reach right down to the bottom of the planting hole. Enough should be given to eliminate any air pockets in the soil. Sometimes the planting area is flooded twice to make sure all the soil is settled.
To hold the water around the roots, make a saucer or a rim of earth so the water will not run off but will soak into the soil. A professional trick is to water gently directly onto the trunk, letting it run down into the soil. This prevents the force of the water from eroding the soft soil.
Most deaths of new plantings are due to incorrect watering –– either too little or too much. Trees mostly die from drought, but they also can die from too much water, for the roots must be able to breathe. Check the soil. If it’s soggy, wait to water. Newly transplanted tree roots take up less water than vigorously growing ones. A hosing or misting of the leaves, however, is very helpful if they appear droopy during hot or windy weather. Sometimes their few roots just can’t absorb enough water to protect and hydrate the leaves.
It is sometimes difficult to tell if the soil has enough water. The easiest way is to dig down a few inches and feel the soil. Another is to buy a water meter, which is not expensive. While water meters are not completely accurate since their readings depend on dissolved salt levels in the soil, they are extremely useful. The quickest way is to look at the leaves. When under water stress, they begin to droop. It takes some experience to know what their natural look is, and what is drooping. As a rule of thumb, happy leaves are held modestly horizontal, while stressed ones have a hang-dog look.
The best way to handle watering of new trees, however is to give each tree 10 gallons of water each week for the first year, rain or shine. More for larger specimens. Twice a week may be needed in desert, very hot, or windy regions. If there is one thing that will make the most difference between success and failure, it is 10 gallons of water once a week!
At planting time, the water used for the backfill may be enriched with a very weak soluble fertilizer solution, or one of the newer organic transplant enhancers or planting hormones (Rootone, Transplantone, or Roots). The hormones help the plant roots get established. Nurseries use liquid fertilizer for foliar and root feeding, but understand what you are giving, and don’t overdo it. Don’t incorporate granular fertilizer in the backfill soil as it will burn the new roots. Regular surface granular fertilizing should not begin until the late fall after transplanting, or the following spring. The idea is to let the transplant make new roots before pushing new leaves and stems with fertilizer. If the roots aren’t there, the plant can’t support the top growth.
A good 2-inch mulch over the entire root area helps keep the soil moist and cool, which is essential to root regeneration. The mulch should not be piled against the tree bark, not should it be deeper than the 3 inches. Mulch that is too thick encourages undesirable anaerobic bacteria, and restricts gaseous exchange between the soil and the air.
Trees do not need to be staked, except if they have heavy tops, or if the area is very windy. Stakes should be removed after several months when new roots have formed, and certainly in a year. Trees develop much stronger trunks if they are allowed to sway in the wind, unstaked. Any trees that become crooked or leaning, however, should be straightened immediately with appropriate tree stakes or guy wires. These should be kept on until the trees are growing upright and have very stable root systems.
Transplanting time is a good opportunity to prune the crown into a good, well-balanced shape. It was believed at one time that at transplanting time one-third of each branch should be removed. But recent field tests showed these "haircuts" to be unnecessary. A tree puts out the same quantity of leaf surface whether on shorter or longer branches. After the tree leafs out, however, one should prune out sickly branches that aren’t growing vigorously.
Almost any tree can be successfully moved if it is dug carefully, not allowed to wilt or dry out while out of the ground, planted in good soil, and watered once a week for the first year. The shorter the time a plant is out of the ground, the better the rate of success will be. If a plant cannot be immediately placed in a new hole, its roots should be kept moist and covered. Bare-rooted plants may be immersed in a slurry of water mixed with mud. This will protect the delicate root hairs for several days. Balled-and-burlapped plants, and especially container-grown ones, need to be water frequently. Container plants need water daily, sometimes even more often. The tops should also be sprayed with water if they droop at all. And they all need protection from sun and wind, especially while being transported in cars or trucks.