By: Sandy Feather
Penn State Extension
Q. I am concerned about the damage to plants in my yard following our recent cold snap. Our beautiful, albeit early spring had new growth emerging on hydrangeas, butterfly bushes, maples, and viburnums, and my hostas and daylilies were pushing up nicely. It is depressing to walk around the yard and see how the cold has killed back all that new growth. Should I cut the damaged foliage back on my daylilies and hostas? I imagine the blooms will be fine, but the foliage will not look very good, even later in the summer, if I don't do something.
A. Although it is not unusual for us to have a cold snap, and even some snow in April, temperatures in the twenties and teens for such a long period after plants started blooming and leafing out has caused similar damage to plants throughout the eastern United States. Daffodil, forsythia and magnolia blooms are history in many areas, and the tender new foliage on trees, shrubs and perennial flowers has been killed, too.
Herbaceous plants, such as your hostas and daylilies, should recover with no problem. Early spring bloomers like pulmonaria and bleeding heart may not bloom properly until next spring, but the plants themselves will be fine. Go ahead and cut the damaged foliage back to within a few inches of the ground. The damaged leaves will grow out, and more new leaves will push up as temperatures warm. You won't know anything happened to them by summer. Avoid cutting bulb foliage back before it yellows and dies on its own. Those leaves, through the process of photosynthesis, will create the carbohydrate reserves necessary for bulbs to flower and thrive next year.
Trees and shrubs that had their new growth killed back should also recover with no problem. They will send out a second flush of leaves - many area doing so already. It would not be great if the second flush of growth is killed by a later frost - that could be stressful for affected plants. Trees and shrubs "spend" their carbohydrate reserves in putting out new growth. Having to do so a third time might not be a problem for otherwise healthy plants, but those stressed by other factors - they are the wrong plant for a given site, they have been improperly planted or damaged by construction, or if they suffer severe insect or disease problems - may not bounce back as well.
It would never hurt to give these plants a little extra TLC through the growing season. Be sure to supply supplemental water when we get into hot, dry summer weather. Most plants need an inch of water a week to thrive. Although fertilization can help in some situations, it is not a cure-all, and should be based on soil test results. Excessive fertilization can make plants more susceptible to injury from insects that feed with piercing-sucking mouthparts, such as aphids, mites and leafhoppers, as well as certain diseases.
Hold off on cutting back your butterfly bush (Buddleia spp.) until late April or early May, when we are usually past danger of a hard frost. Along with artemesia (Artemesia spp.), blue-mist shrub (Caryopteris spp.), St. Johnswort (Hypericum spp.), lavender (Lavendula spp.),and Russian sage (Perovskia atriplicifolia), butterfly bush is sensitive to late spring frosts. These plants often die when cut back in fall, and it is generally recommended that you wait and cut these back in late spring. Don't panic if you have cut yours back already - just be prepared to cover it up if frost threatens.