Just a couple of weeks ago when Santa Claus opened the front door to the North Pole to start on his annual rounds, he unleashed a slug of unconscionably cold air, the likes of which we haven’t seen in more than 25 years. And in last week’s column we covered a more or less generalized discussion about what happens in plants when exposed to such inexcusable weather conditions and how best to respond.
As the 345 quadrillion emails sitting in my in-box can attest, there are lots . . . and I mean lots of questions about very specific things to either do or not do to plants out in the garden in the wake of the polar blast. So . . . let’s get specific . . .
Broadleaf Evergreens – starting with a wide lens.
The reason it looks like these plants took the brunt of the weather is because . . . well . . . they have leaves that can show cold damage. The oaks and maples and dogwoods – they dropped their leaves, as they always do, in preparation for the oncoming winter. Deciduous plants simply have no leaves left around to show any damage. Deciduous plant stems can be just as dead as broadleaf evergreen plant stems. It’s just that the deciduous types don’t show it as clearly.
The other thing about broadleaf evergreen leaves is that they are the most sensitive of the plant’s above ground parts when it comes to cold temperatures. The leaves are damaged first. Then as it gets progressively colder, you lose the finest and youngest stems followed by the larger branches and finally, the main trunk. The easiest way to put this in blunt, gardener vernacular is, the juicier the plant part, the less cold it can handle. Think lettuce . . . tomato . . . apple . . . acorn . . . trunk of a big, fat, 300-year-old oak tree . . .
Hollies – the evergreen types.
We clearly love our hollies in and around Kentucky. We grow a long list of species and varieties – and they all differ in their ability to withstand extreme cold. So if you’re walking around the neighborhood and wondering why your 8 foot American holly (Ilex opaca) is brown as a hammer and your neighbor’s is as green as can be, it’s not necessarily that you’re a worse gardener. Could just be a different variety . . . or different sun exposure . . . or different soil . . . or was pruned at a different time . . .
The most tender holly varieties dropped their leaves as soon as the cold snap was over. But most hollies with damage took about a week or so for them to start dropping their leaves. It’s not that the leaves just now died. That happened two weeks ago. The leaves are just now finding out!
Recommendation: Wait until new growth starts in late May to determine what lived and died – and then
you can prune away any dead stems. Fortunately, hollies bounce back fairly quickly.
Nandina (Nandina domestica)
These multi-stemmed shrubs lost all their showy fruit in the cold. And some of the stems were likely killed back as well. The good news about Nandina is that plants tend to resprout from the base quite well.
Recommendation: I’d still wait until spring to check for dead branches and if there is considerable damage to stems and buds, you might just cut the whole thing back to the ground. You’ll lose a year of flowers and fruit (if the shoots are damaged you’ve lost the flowers and fruit already, anyway) but you’ll likely have a good quality plant for the future.
Cherry Laurel (Prunus laurocerasis)
Cherry laurels love to drive us crazy with browning leaves. Usually they are durable workhorses in the landscape but if it gets just a little bit too cold, and if they get a little too much sun during the cold, they can end up looking like a row of 8-foot-tall brown paper Kroger bags. And at the temperatures we had two weeks ago it is likely that they sustained considerable stem damage as well.
Recommendation: Sit on your hands and do nothing right now. Wait until spring, see what’s leafing out and cut out the rest. If plants have died back to near the ground, go ahead and cut them all the way back. Odds are, as long as you’re not dealing with a 50-year-old plant, you should get some regrowth.
On the deciduous end of the spectrum, the basic rule again is going to be to sit and wait. The most likely damage will come from some pretty well-known favorites.
Crepe Myrtle (Lagerstroemia species and hybrids)
About every 3-6 years our crepes tend to have a bit of an involuntary reset. They’ll either lose the top 6-12 inches of the youngest shoots, 4 feet of growth, or in the worst of years they might die all the way back to the ground. The problem is they tend to be a bit inconsistent from one year to the next. Zero degrees might create damage one year but not the next. A good reminder that we quite simply don’t know everything that’s going on out there in the garden!
Recommendation: If your crepes experience some stem damage/die back, resist the urge to give the plant a Three Stooges haircut. Instead, take your hand pruners and individually cut back damaged stems to remove all the dead wood. Then step back and plan a few more cuts to make the resulting plant look like a tree rather than an umbrella on a stick.
Flowering Dogwood (Cornus florida)
Not that you’ll be able to tell right now, but this spring we might be in for what we call miracle dogwood year. That’s when it gets cold enough to kill off the two outer floral bracts while leaving the inner bracts undamaged. When that happens, you get flowering dogwoods with 2 white “petals” rather than the normal 4.
Recommendation: Sit back and enjoy the show. There’s nothing for you to do here!
Of course there are scores of plants out there, some showing damage now and others that will show it later. The best you can do is be patient, study your plants to know how they grow, and just follow their lead.
As for Santa’s meteorological Christmas gift to bad behaving gardeners, I pray that next year he juststays with coal!
This article was originally submitted to the Courier Journal on January 10, 2023.