Fielding Questions: Deer damage, trimming geraniums, quackgrass in peonies

Q: In 20 years we’ve never had this problem, but this year deer attacked our arborvitae shrubs, as shown in the photo. Will they survive, or what should we do to save them? — Kevin S.

A: The soft green foliage of an arborvitae is like a fresh salad for winter-hungry deer. I wish I had better news, but when rabbits or deer consume all the outer foliage from arborvitae branches, leaving nothing but bare inner twigs, that’s often the way the shrub will remain for its lifespan.

You can often tell arborvitae that have been browsed in the past, because all the foliage is absent from large sections where feeding occurred. Older inner wood of evergreens is usually not capable of regenerating foliage to fill in bare spots.

The deer-damaged arborvitae will survive, with its bare bottom, likely for the life of the shrub. There is really nothing that can be done to revert the damage, but the shrub itself will continue living.

I would definitely wait and see what happens. It would be rare for the bare branches to produce new foliage, but if the deer didn’t consume all the younger outer buds, there’s always a remote chance something might grow.

You will know by the end of May if new growth is emerging. If rainfall is scarce this spring, soak deeply every one-to-two weeks. You might also try fertilizing the shrub to encourage growth, either a tree type granular form, or a water soluble type.

Q: I’ve been growing geraniums under lights ever since I brought them indoors last fall. They’ve grown very well, but should I be trimming them a little? It seems like they’re getting a little large. — Nancy B.

A: Growing geraniums indoors is a great way to preserve them from year-to-year, either from cuttings taken in the fall, or by bringing in the original plant. Geraniums grow well under fluorescent or LED lights, or in a sunny window.

Geraniums benefit from cutting back in early March, which encourages fresh branching from the base and by May the plants will be ready to return to outdoor planters. I trim ours back by about one-third by mid-March.

Geraniums can also be wintered indoors in a partially dormant state. When homes had humid, cool root cellars, many gardeners wintered geraniums there, sprinkling only occasionally.

Today’s homes often lack rooms cool enough to winter dormant geraniums the way gardeners once did, but a few still do.

Q: Our peony plant has been invaded by quackgrass, and we’ve tried pulling it, but of course the grass returns. Is there anything we can do this spring? The peony is otherwise healthy, and we hate to dig it up and disturb it just to remove the grass. — Dan L.

A: There are several effective herbicides that specifically kill only grass-type plants, and they won’t harm non-grass plants when used as labeled. Three common brands are Ortho Grass-B-Gon, Bonide Grass Beater and Hi-Yield Grass Killer.

These grass-killing herbicides can be sprayed right over the tops of actively growing peonies and other non-grass perennials or shrubs. In most cases the quackgrass needs to be at a young and tender height of about four inches in spring or early summer. Read and follow label directions.

I’ve found these products to be very effective in removing quackgrass, but patience is required, as it takes time for results to be seen. Quackgrass also has dormant underground buds that usually spring into action when the first growth flush is killed, so a repeat application might be needed if a second wave of quackgrass emerges.

If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at donald.kinzler@ndsu.edu . Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.