Out-of-control forsythia

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on January 15, 2008 at 1:31 PM, updated January 15, 2008 at 1:36 PM

By George Weigel/The Patriot-News

Q: I have a stand (patch, thicket, jungle) of old forsythia that's completely out of control. They're planted to the southeast of a line of Norway spruce trees, so they don't get any western sun. The forsythia canes have all grown toward the southeast and now span more than 20 feet in that direction. They aren't even blooming very nice anymore and are creeping out into area I'd like to keep mowed. How hard can I prune these back without risking their survival?

A: Forsythia are very tough customers and respond well to "rejuvenation pruning" and even near total cutbacks. I suspect you could chainsaw the whole forsythia jungle to the ground, and it would make a comeback.

I'd start out by taking the whole thing down to somewhere between ankle high and a foot - or at least back a little below whatever height you'd like to keep them. Then I'd shovel and/or ax out any roots that are creeping into areas where you don't want them. Third, use a lopper to cut some of the biggest, oldest shoots right to the ground to air out the stand a bit.

This should give you a better looking display and a better bloom - even considering the vigorous competition from the spruce roots and the partial shade these evergreens are causing. The best time to do this pruning is right after the forsythia bloom this spring. That way you'll get what flowers already have budded. Winter pruning won't hurt the forsythia plants, but you would eliminate most (if not all) of this spring's flowering.

Once the hulking jungle is back under control, shear it back after bloom each spring or do the thin-and-shorten routine, depending on your preference of looks and the time and energy you have to devote to this job. No need to join a health club when you've got a big planting of old forsythia...