A shoot growing from a plant's roots or base of the trunk (especially on grafted plants), often more vigorous than the desired variety and needing removal.
In plain terms
Suckers grow from roots or the base of trees, especially on grafted trees (from rootstock below the graft union). They're often thorny, more vigorous, and of poor fruit/ornamental quality. Removing them prevents them from taking over the plant. On grafted plants, remove suckers immediately (they're often the rootstock variety, not the desirable scion).
Why this matters
Ignoring suckers allows them to take over, weakening or replacing the desirable variety. Regular sucker removal maintains plant quality.
In practice
Examples
Grafted apple tree: rootstock suckers emerge from base; remove them immediately.
Rose bush with thorny suckers; remove to maintain ornamental quality.
Elm with root suckers; remove to prevent them from becoming small trees.
Flowering cherry suckering vigorously; removes energy from main tree; eliminate.
Practical applications
Check grafted plants regularly; remove suckers as they appear.
Cut sucker as low as possible; painting cut with herbicide prevents regrowth.
On non-grafted trees, single sucker occasionally acceptable; multiple need removal.
Remove suckers before they grow large; easier when small.
For persistent suckers, herbicide application prevents regrowth.