Why Is My Plum Tree Producing Suckers from the Roots?

Vigorous upright shoots appearing from the soil around the base of a plum tree, or sometimes several metres away along a surface root, are root suckers. In grafted plum trees — which is virtually every garden plum sold commercially — these suckers come from the rootstock rather than the fruiting variety grafted onto it. Left unmanaged, they compete with and can eventually overwhelm the tree you actually want to grow.

Why do suckers appear from plum rootstocks?

Commercial plum trees are grafted — the fruiting variety is joined to a rootstock, typically St Julien A or Pixy, that controls tree size and provides root system characteristics. The rootstock itself is a different plant (often a wild cherry plum or other Prunus species) that naturally produces its own shoots when the roots are stimulated or damaged. Cultivation near the root zone, lawn mowing over surface roots, or simply the rootstock's natural vigour can all trigger sucker production.

Identifying rootstock suckers

Rootstock suckers often look different from the variety above the graft union — they may have smaller, differently shaped leaves, different bark colour or a more vigorous, upright growth habit. A sucker appearing well away from the trunk base is almost certainly from the rootstock. Suckers from below the graft union on the main stem are also rootstock suckers. Sucker growth from the variety above the graft is uncommon but does occasionally occur from adventitious buds on the trunk — these should still be removed.

How to remove suckers correctly

Cutting suckers at soil level is the least effective approach because it stimulates the dormant buds at the cut point to produce multiple replacement suckers. The correct method is to trace the sucker back to its origin on the root, expose the connection point, and pull or tear the sucker away from the root rather than cutting it. This removes the dormant buds at the base and dramatically reduces regrowth. Perform removal at any time of year, though summer is preferred for all stone fruit work.

Preventing sucker stimulation

Avoid cultivating the soil within the drip line of the tree with a fork or spade — this severs surface roots and each cut root tip has the potential to generate suckers. Keep the root zone mulched and weed with a hoe rather than digging. Mowing over surface roots with a sharp mower blade also generates sucker growth — trim carefully around trees.