Some shrubs and trees won’t survive root damage if moved, but most make a good recovery if handled carefully, and moved when comparatively dormant.
What is the best time to transplant trees?
Midwinter is the safest time for most. Exceptions are semi-tropical or warmth loving trees such as gardenias, acalyphas, and, in cool districts, hibiscus and citrus. The latter two would be best moved in early spring, when the worst of the cold is over but before new growth starts.
Move conifers in late autumn. Winter is second choice, and fairly safe. They move comparatively easily if not too large.
Trees that rarely survive moving include many native eucalypti, wattles, most grevilleas, banksias, pittosporums, and imports such as luculia, virgilia, bauhinia, daphne, diosmas, etc.
The surest are the deciduous trees moved when dormant, but many hard leafed evergreens are also reasonably safe: Camellias, citrus, cotoneaster, azaleas, holly, hibiscus, most viburnums, rhaphiolepis, abelias, oleanders. The last two, especially, need to be cut fairly well back.
With care, very large trees can be moved successfully. In Japan, a small forest of native ginkgos was moved to landscape the Olympic Games, but there is a limit to the size of tree worth moving, especially for the home gardener.
Apart from effort and manpower needed, the shock may be so great, that although the tree survives, it makes poor growth and never picks up.
Large trees should be conditioned gradually before a move. Mark a circle around them with a radius about four times the diameter of the trunk. Divide the circle into six or eight segments, and remove the soil in about a foot-wide trench from alternate segments.
The trenched sections are refilled with well-composted soil and fertilizer after jagged roots have been cleanly trimmed. Three to six months later, trench the remaining segments and treat as the first.
The soil within this circle is kept well watered, and new root growth mats in it. Later, a wide trench can be made outside this area, the newly formed root ball wrapped in hessian, base roots severed, and the tree finally lifted.
This is rather too involved for most home gardeners, but there is a modified version. For example, roots of the tree to be moved, could be severed gradually.
First place a few short stakes to mark a circle round the trunk, its radius about four times the trunk’s diameter. Thus a tree with a trunk 3 inches across would be surrounded by a circle 12 inches in radius or 24 inches diameter – involving quite a weight of soil.
Plants such as thin-stemmed, tall camellias should have this circle a minimum of 7 inches from the trunk. Young camellias could be lifted right away, but for more doubtful ones, try this: Spade down almost vertically, but sloping slightly under the plant, to full spade depth, at alternate spacings around the circle. The idea is to cut half the lateral roots.
A few months later, if it is a safe time to make the move, spade the entire circle again, this time an inch or so outside rather than inside the mark.
Where the soil ball is only about 14 inches across, the plant usually can be lifted by spading around again and levering up gradually. Slip the root ball on to a sheet of canvas or hessian and carry the plant on this to its new prepared site. The new hole needs to be 1 foot wider than the root ball, or there will be no room to pack properly with soil, and dry air spaces may prevent new roots from developing. Make sure that the tree is not replanted deeper than before.
Here, the depth of the initial spading needs to be deeper – about the same as the radius of the surrounding cut. This calls for a trench rather than spade cuts.
Most deciduous trees can be dug and moved safely in one operation, but for large evergreens it is safer to trench about halfway around the tree, taking out a segment on either side. Cut large roots cleanly with a pruning saw.
Fill in for at least a few months, then open the complete trench when ready to move the tree. This trench will need to be widened to 18 inches or so in two or three sections, allowing room to spade under and cut roots below the soil ball.
Also, cut well down on one side, forming a ramp so the tree can be manoeuvred out more easily.
After cutting in well under the root ball, rock the plant on to one side. Try moving it by levering below the root ball with a stout pole, using a wide piece of board to spread its force so it doesn’t bite into soil and roots.
Once the tree is movable, rock it on to a sheet of canvas or hessian and drag it out. The correct procedure is to wrap the root ball carefully in hessian, then bind with stout ropes which are tied to a hessian-bound part of the trunk. Lash lengths of timber under these ropes as carriers.
If the move is only a short one, the tree can be half dragged, half carried on a bag without elaborate wrapping.
You can spade off a fair amount of the outer soil on deciduous trees, but for evergreens keep the root ball as intact as possible.
Points to note: Whether a tree is dormant or not, you must keep the roots moist during the move. If there is any delay, hose frequently with a fine spray, or cover with wet sacking.
When moving a plant, the soil should be just damp. The root ball will then hold together easily.
When a plant’s root area has been suddenly reduced, it will have a better chance of survival if the top growth is pruned back to reduce foliage. This lessens the demand on the roots.
Remove about two-thirds of the foliage of a large evergreen, pulling leaves off it you don’t want to cut branches. Remove young, sappy growth, as this is the most demanding – although the move should be carried out before this appears.
Young evergreens such as camellias won’t need pruning if moved carefully.
Vigorous top canes of deciduous trees are usually shortened by two-thirds.
Roots of azaleas and rhododendrons are close to the surface. In this case spade well out, if possible almost to below the outer foliage, but go down only about 5 inches. Then slant in nearly laterally below the plant.
Lift gradually all round until it moves freely, then slide on to a sheet of galvanised iron or a wide board.