How Short Can You Cut Box Elder Bushes?
Box elder (Acer negundo), hardy in U.S. Department of Agriculture plant hardiness zones 2 through 10, is not a bush or shrub, but a maple tree that bears a slight resemblance to an elder (Sambucus spp.). The deciduous maple species grows between 30 and 50 feet tall, with an equal spread. Box elder thrives in damp, sunny places. It is vigorous and will usually survive being cut back almost to the ground. Pruning the resultant shrub-like growth would be somewhat different than pruning a box elder that was left to grow in its natural tree form.
Cutting box elder to ground or near-ground level will eliminate the leader or central trunk of the tree. Resprouting from the stump, coupled with the species’ tendency to produce abundant root suckers, would then result in a multi-stemmed plant with a rapid growth habit. After the initial severe pruning, the box elder can be maintained subsequently at whatever size and shape fits the landscape situation. However, pruning repeatedly to ground level might weaken or kill the plant and would limit size. Box elder may grow up to 25 inches in one year.
Pruning Tree Forms
If the box elder is growing in it natural tree form, it can be kept lower than its maximum height. To do this, determine the desired height and remove large branches above that point. Use sharp loppers or a pruning saw, disinfecting with a cloth dipped in household bleach between cuts. It is critical to prune in a way that does not weaken the tree. Cut each large branch at the point where it meets a lower, lateral -- horizontal -- branch. Do not leave a stub of the large branch. Continue this procedure until all the large branches have been pruned.
The best time for pruning box elders, whether or not they grow in shrub form, is late winter, before active growth has started for the year. This also allows for removal of weak or dead branches. Box elder tends to “bleed” sap when pruned at this time. Though sometimes unsightly, this is not dangerous. The alternative is to wait until the plant is fully leafed-out in spring and prune at that time. When pruning the tree form, it is best not to remove more than one quarter of the total plant.
Instead of pruning box elder so severely that it grows in shrub form, it might be be better to substitute American elder (Sambucus canadensis), hardy in USDA zones 3 or 4 through 9, depending on variety. American elder is a true multi-stemmed shrub, with compound leaves similar to box elder. It also shares box elder's rapid growth rate, but tops out at a smaller 5 to 12 feet tall with a rounded habit. American elder is also suitable for similar conditions -- consistently moist, sunny sites. It can be cut back to ground or near-ground level.
- Missouri Botanical Garden: Plant Finder – Acer Negundo
- Missouri Botanical Garden: Plant Finder – Sambucus Canadensis
- University of Minnesota Extension: Pruning Trees and Shrubs
- Manual of Woody Landscape Plants, Fifth Edition; Michael A. Dirr
Elisabeth Ginsburg, a writer with over 20 years' experience, earned an M.A. from Northwestern University and has done advanced study in horticulture at the New York Botanical Garden. Her work has been published in the "New York Times," "Christian Science Monitor," "Horticulture Magazine" and other national and regional publications.