We are often asked how close can a fruit tree be planted to the wall of a house. There two main kinds of concern:
- On certain clay soils houses can develop cracks by the action of tree roots. The risk is related to the size of the tree and therefore, in the case of fruit trees, on how dwarfing or invigorating the rootstock is. A rule of thumb for other trees, on at-risk soil types, is to have a separation distance at least equal to the mature height of the tree. For fruit trees grafted on dwarf rootstocks that means 3m or so, and for fruit trees on vigorous rootstocks allow 6m or more.
- Fruit trees, like other trees, can also be a nuisance. They can grow to block light, abrade the fabric of a building as they sway in the wind, damage fences by growing through them or cause damp. Roots can push up paving stones, fallen leaves can clog gutters and drains, and paths can be made slippy. Even the fruit, if not picked, can attract wasps and be unsightly. Bear this in mind when considering where to plant your new young fruit tree!
Fruit trees can often be planted closer to buildings than large ornamental trees because the rootstocks constrain the spread of the roots. In this respect fruit trees are often a better choice than ornamental trees if you are planting near to the house.
Sometimes planting a tree next to a wall, which may or may not be part of a building, is a good idea. Walls, especially south-facing ones, provide a sheltered and relatively warm microclimate that favours some fruit trees, especially if trained against the wall as a fan or espalier. Wall-trained trees should be planted at least 20cm (8 inches) from the wall to allow for the radial growth of the trunk. To keep root problems to a minimum, dig the planting hole about 20cm-40cm away from the wall, and lean the young tree into the wall, so that the roots are away from the base of the wall. You can also prune the roots on the wall side, and if necessary protect the back of the planting hole with paving slabs. In general you are not likely to experience structural problems from the roots of a semi-vigorous fruit tree in this situation, and such a tree should be capable of growing 3m-4m across and 2m-3m high.
If in doubt, seek the advice of a professional arboriculturalist or consult the book The A-Z of tree terms: A companion to British arboricuture.