Best time to transplant trees, shrubs is right around the corner

At Shead High School in Eastport, where I teach, colleagues recently asked about transplanting trees and shrubs from one spot in the landscape to another. Principal Terry Lux stopped by the classroom to ask about moving small white pines from the back of her property to the front. And fellow teacher Katherine Lee wants to move a few plants from a large forsythia hedge at her old home to her new landscape.

Transplanting season is fast approaching. Young trees, such as Terry’s pines, and established plants of some shrub species, such as those old forsythias, can be successfully dug and moved in spring as soon as the soil can be worked. I much prefer moving a plant in the spring, rather than the fall, giving it a full growing season to produce new roots, replacing those lost during the move.

If given a choice about the size of plant to transplant, smaller is always better. You can move a much larger percentage of the plant’s root system when you transplant a small tree or shrub. For example, Terry should be able to move a small pine seedling, perhaps no larger than 12 to 15 inches in height, with most of its roots intact. This will mean only a single growing season of intensive care, including weekly watering, compared with several years for a larger plant. The same rule of thumb that is used when purchasing plants at the nursery can be applied when moving plants about the garden: Plan on one year of intensive care for each inch of trunk diameter.

What about Katherine’s old forsythia shrubs? Would it not be better to simply purchase younger plants from the garden center? Yes, if the same variety could be found today. But if Katherine wants to move some plants from that old hedge, I have no doubt that she can succeed.

Successful transplanting is likely with established forsythias and similar species, such as the spring- and summer-flowering spireas, as long as you can move a substantial portion of the root system with the basal crown. Start by pruning all of the old stems to within 6 inches of the ground. Then dig up the crown, along with as many roots as possible, and move it to the new location. For large, old plants with huge crowns, a backhoe works well.

As the plant becomes established in the new site, young shoots will grow from the basal crown and from buds on the old stumps. Pay close attention to watering during the first growing season, ensuring an inch of water every week, by rain or hose.

When transplanting any plant, dig as large a root ball as you can manage. And before digging any plant for transplanting, first dig the hole in the new location. Dig big holes! The new hole should be twice as wide and as deep as the root ball. Do not amend the backfill soil with organic matter, such as peat or compost. Recent research has shown that amending the backfill actually hinders establishment of the new root system. Hopefully, there will be little difference between the soil conditions of the old and new sites.

Next week: When is it necessary to root prune before transplanting?

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to reesermanley@shead.org. Include name, address and telephone number.