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Do’s and Don’ts of Post-Freeze Tree and Shrub Care

by Dr. Deborah Hill, Ph.D.

After five consecutive nights of freezing temperatures, many of our flowering trees and shrubs (and bigger trees) have frozen foliage and flowers. Most trees and shrubs are capable of putting out a second set of leaves (but not flowers) for the rest of the growing season, but that activity stresses the resources of the plants.

There are several things that can be done to care for these stressed plants…

• Make sure the plant does not suffer from drought for the remainder of the growing season. A rule of thumb is that it will need the equivalent of one inch of rainfall per week. Water it - once a week is probably fine - when we do not get that much rain.

• Mulch the plant with some form of woody mulch (it lasts longer). This can be commercial mulch, sawdust, wood chips, or similar material. Check with people in horticulture or forestry to see if there is any kind of mulch you should NOT use with a particular plant. Mulches serve as blankets that protect both temperature and moisture in the root zone. Place mulch 2 or 3 inches DEEP around the plant, in a circle that extends out to the edge of its crown. Make sure to leave a “breathing space” right next to the bark – don’t pile mulch up against the stem/trunk of the plant. (Mulching also protects the trunks of your plants from mower damage!).

• Wait a couple of weeks to a month to see how the plant will recuperate (mulching and water monitoring should be done right away). Prune off obviously dead material, and consider pruning to reduce the overall size of the crown of shrubs (trees may be a little too high to manage this way). A smaller crown will make a smaller demand on the roots for re-growth.

• Remember that stressed plants can attract both insects and diseases, so monitor your plants carefully for the next month or so, and treat these other problems as appropriate if you see evidence of them.

• Panic! Trees especially have seen (and weathered) a lot of abuse in their lifetimes and will weather this event, too. Help them out if possible, but don’t give up on their ability to regenerate.

• Add fertilizer to the plants at this time. Fertilizer tends to increase TOP growth on the plants, and the roots are already stressed to produce a new set of leaves with whatever reserves they still have. Adding fertilizer at this time would stress the roots further. You MAY add fertilizer this fall to help the plants through next winter…