Extension Educator, Horticulture
The old saying goes "Everything is better when it's fried". Some may believe that with food, but it's certainly not true with landscapes.
Fried is the best description of plant leaves right now. Is it just the cold weather as many have said? Or was it really a conspiracy with several "perps"? In true CSI form, let's look at the evidence. First the victims were vulnerable. We had very warm temperatures in March, so plants had plenty of opportunity to start growing weeks ahead of schedule. According to Jim Angel, state climatologist, the average temperature in March was 48 degrees F which is 7.6 degrees above normal. When leaves first emerge they are succulent and have not "hardened" to environmental conditions.
The recent cold weather is the obvious suspect to the leaves demise. It is common to get cold temperatures and freezing in April, but not to the extreme that occurred. In Champaign it got to 21 degrees F. on April 7. According to Angel the odds are once in every ten years for such cold temperature to occur so late. Geee, aren't we lucky.
But I believe the cold did not act alone. In my mind the wind is as much to blame as the cold for our burnt landscapes. We experienced extremely windy weather before the cold. April 1 was probably the windiest, according to Angel, with an average speed of 18 mph and a peak gust of 53 mph.
March 31 and April 3-5 were also windy with wind speeds in the teens and twenties and gusts in the mid to upper 30's. Most of those winds were out of the west so victims were found leaning to the east. Tender new leaves succumb to extreme winds. In addition plants that normally emerge early such as columbine and bleeding heart naturally have delicate leaves. They didn't have a chance against the wind either.
There is no way to punish the "perps" so what do we do now?
Like a bad perm the top few inches of many of my perennials are fried. Give these a quick haircut with shears to remove the damaged portion. Some plants benefit from this technique as they will develop more branches and grow more compact. This will delay bloom a couple weeks. My plan is to shear sedum, catmint, beebalm, aster, and tall phlox. Pretty much anything that sends up many stems. I would not do this to peonies since you will cut the flower bud off. I'm doing a wait-and-see with columbine and old fashioned bleeding heart and only removing the obviously fried stems and leaves. In Sandy's world these two should still bloom, but I'm not sure I've adequately explained that to them.
With trees and shrubs the chant is "re-leaf or die". Healthy woody plants have enough food reserves to develop another set of leaves. The plants may look a bit ugly for a couple weeks with brown leaves until the new growth appears. I'm guessing we will see a crabapple flower show in our area, since they were still in tight bud before the cold. Same is true for lilacs. The leaves on my plants look horrible but the flowers have not turned brown so I think we will see a lilac show.
The bottom line is: be patient and don't give up on your plants. They are amazingly resilient. It is, however, a stress for the plants to use food reserves to send out new leaves. This is a good time to remind ourselves of proper plant care. Water during drought periods. Generally an inch of water a week through rain or irrigation is a good goal. Mulch with organic materials such as wood chips from your local landscape recycling center.