It’s cold out there.
Temperatures reached zero degrees this year on January 17, the coldest in northern Virginia in more than a decade. We’ve had another couple nights in single digits, and will probably have a few more before February comes to an end.
And then comes 71 degrees on February 11, and a handful more warm days. People break out of their hibernation, walk through their garden and notice a bunch of dead plants. I’ve seen them too. Neighbors show them to me, and customers e-mail pictures.
But, they’re not dead, or often aren’t, even when they appear to be.
Our gardens have some plants that are near the northern edge of their hardiness zone, so when we get a period of unusually cold weather we can expect to see a bit of damage. Even plants that are hardy far north of our area can have some dead leaves due to cold temperatures and low humidity. In most cases it’s just cosmetic and nothing to fret about, they’ll be fine.
Plants that experience winter damage in the mid-Atlantic region
Nandina domestica – is the most common plant to exhibit foliage damage when temperatures go below 10 degrees Fahrenheit. This variety is a semi-evergreen, meaning that it will drop leaves in a cold Winter, and stay mostly evergreen in warmer conditions. New growth begins about the same time that our native dogwoods begin to leaf after flowering around mid-April, but it can be two weeks later in a cool Spring.
Within several weeks new growth opens fully and there will be little or no evidence of the problem. In most cases no pruning is needed to rejuvenate the plant since only leaves are damaged and branches and stems are not affected. Other varieties of Nandina, such as Gulfstream, Moonbay, and Harbor Dwarf, will remain evergreen to colder temperatures.
Otto luykens and Schip laurels – many times will show damage to foliage in the first year after transplant. The cherry laurels are relatively slow to establish after planting, and may have problems with late Fall planting followed by persistent cold. After the initial Winter an established plant will rarely have problems with cold weather.
In most cases a light pruning will remove dead leaves and stem tips, but more severe damage can mean a much longer period for the plant to revive, and possibly determine that the plant needs replacement.
Hollies – minor Winter damage to leaves can be pruned off, and the plant will recover quickly. Small-leafed Japanese hollies are more likely to be all-or-nothing, either showing no damage or being dead.
Boxwood – although extremely hardy, boxwood will suffer damage to leaves that have grown late in the season. These leaves can be the result of pruning in late Summer. The remedy is to prune the dead leaves and branch tips.
Leyland cypress – are all-or-nothing. They do not have vigorous root systems and are prone to problems when planted in mid to late Fall. Problems in the Winter with newly transplanted leylands usually result in death. After the first year, leylands rarely have Winter issues.
Crape Myrtle – often grow and bloom well into September, so branches do not have an opportunity to mature, or “harden off” prior to the onset of cold weather. Thus it is common, even in the deep southern states, to experience some dieback on the tips of crape myrtle branches. Sometimes dieback is no more than an inch or two, but it can be a foot or more.
Also, crape myrtle are just about the last plant to leaf in the Spring, often showing no growth until late April or early May. Don’t worry, the varieties we plant are quite hardy and rarely die from cold in our area. Wait until you see new growth before pruning out dead wood.
Japanese Maples – every year Japanese maples will have some dead branches, and some varieties will experience some tip dieback. Almost all varieties are extremely Winter hardy for our area, and will be fine once the dead wood is pruned.
Birch – will usually have some small dead branches, in particular lower branches. After the trees have leafed, prune the dead.
Azaleas – most varieties will shed some of their leaves early in the Winter, and many change leaf color. New leaves grow after blooming, which, for most azaleas is in mid to late April. If they have a stray dead branch it can be pruned at any time.
Hydrangeas – will often have some dead tips. When new growth comes out in early April prune just above the top leaf. For older hydrangeas pruning dead tips will usually mean no blooms, since the flower buds formed immediately following last year’s bloom. Newer types such as Endless Summer and Penny Mac bloom on old and new wood, so they will flower dependably regardless of Winter weather.
Why not plant hardier varieties?
These are all hardy plants. There are many plants that are susceptible to cold injury until they have established a good root system, and thereafter are quite sturdy. And others that will do fine unless cold comes early in the Fall. The worst weather for most plants is cold and windy with low humidity. This combination will cause problems for most broadleaf evergreens, especially if we have had a drought through Summer and early Fall.
If you are in doubt whether a plant is dead or has just suffered some damage contact your garden center or landscaper, or e-mail them a photo. In the pictures above all plants will revive nicely in the Spring after some minor pruning. Don’t give up on a plant that appears dead too soon. Many times this is a natural cycle, and if you start over with a replacement you might have to go through it again the following Winter.