Why Is My Cherry Tree Growing Too Large?

Cherry trees on vigorous rootstocks can reach 8–10 m in height and spread within a decade, making them unmanageable for netting against birds, difficult to prune safely, and unsuitable for small gardens. If your cherry tree is growing much larger than you expected or than your garden can accommodate, the answer almost certainly lies in the rootstock it was grafted onto when it was propagated. Understanding rootstocks is the key to managing — or planning to replace — an oversized tree.

Understanding cherry rootstocks

Unlike ornamental cherry trees which may be grown on their own roots, fruiting cherry varieties are always grafted onto a rootstock — a different variety or species of cherry chosen specifically for the root system it provides. The rootstock controls the tree's vigour, ultimate size, how soon it begins fruiting and its tolerance of different soil conditions. The graft union — a slightly swollen or offset area on the lower trunk — is visible on most trees and indicates that the tree is a grafted specimen.

Common rootstocks and their sizes

The most widely used cherry rootstocks in gardens today are: Gisela 5 (dwarfing — tree reaches 2.5–3.5 m, earliest fruiting, needs good soil and irrigation); Gisela 6 (semi-dwarfing — 3.5–5 m, more vigorous than G5, better for less fertile soils); Colt (semi-vigorous — 4–6 m, robust, tolerates heavier soils, widely used in older plantings); and Mazzard/F.12/1 (vigorous — 8–10 m or more, mainly used in commercial orchards and old cottage gardens). Trees described as "standard" or old garden cherry trees are almost always on Mazzard or a similar vigorous stock.

Pruning to manage size

Summer pruning can restrict growth to a degree by removing extension growth and reducing the photosynthetic area, but it cannot override the fundamental vigour programme dictated by the rootstock. Annual summer pruning to remove strong upright extension shoots and open the canopy is the main management tool for keeping a vigorous tree within reach. Accept that a tree on a vigorous rootstock will still require significant ladderwork each season and plan accordingly.

When replanting is the better answer

If the tree is in an unsuitable position, is too large to net effectively, or is still young enough that starting again is practical, replanting with a tree on Gisela 5 rootstock is the best long-term solution. Gisela 5 trees planted in good soil will begin fruiting in their second or third year, making the transition relatively painless for a gardener who has had years of frustration with an oversized tree.