Is regrowth on apple tree the variety or the rootstock?
Frank Helliwell, by email Frank Helliwell, by email
Stefan says: This is an interesting conundrum. You have a young ‘Discovery’ apple tree grafted on the rootstock M26. During a gale last winter, a large branch from an oak tree broke and crashed on to it, snapping the stem at about 20cm (8in) above soil level. You decided to leave the tree to see what happened and this year it has grown again with several new shoots, but you need to know which ones are rootstock and which ones are ‘Discovery’.
The leaves of apple rootstock and variety are usually similar and therein lies your problem. However, apples are planted with the graft union above soil level so you should look for a small swelling at the base of the plant. This marks the position of the graft, and any shoots arising from above it will be of the variety, and any from below it will be of the rootstock. It should be possible to select the best of the shoots arising from above the graft and retrain the plant, while cutting off the rootstock shoots.
The problem is similar to that facing rose growers in recognising suckers emerging at the base of the plant. With roses, however, suckers usually arise from below ground because the plant should have been planted with the point of union between rootstock and variety about 2.5 cm (1in) below soil level. Moreover, the leaves of rose rootstock and variety usually differ in appearance.
Not all gardeners may be aware of how frequently nurserymen graft a wide range of different ornamental plants as well as fruit trees, and the breeding of special rootstock varieties has become highly significant. And with apples and some other fruit trees, grafting on to a growth-limiting rootstock like M26 means the tree will remain at a manageable size.