Extension Educator, Horticulture
Shriveled brown leaves are a common site after our recent nighttime freezes. Many trees, shrubs and perennials that were in the full swing of spring growth suffered as temperatures dipped into the twenties. Damage is caused when ice crystals form inside plant cells and rupture the cell walls. New leaves and stems look limp right after a freeze. Frost tolerant plants such as broccoli have durable cell walls that resist rupturing.
High winds compounded the injury to new leaves. I wonder on many plants if it was more wind than cold that caused the damage. Whenever plants are in active stages of growth the new leaves and stems are very tender and succulent. New growth does not tolerate the cold and wind that would cause a mere shudder in older, tougher-skinned growth.
Some of the reported species damaged by frost include: catalpa, English and black walnut, golden rain tree, Japanese maple, hackberry, gingko, hydrangeas, magnolia, mulberry, sumac, ash and the list continues. It may be easier to list what didn't get damaged.
The new growth of yews, spruce and boxwood were killed in many areas. The damage appears as bleached or brown leaves on bent or hooked stems. These can be lightly pruned now to remove the dead tips.
I asked Master Gardeners what plants experienced the most damage in their yards. You can look at their comments as well as report your own plants on our Facebook page. http://www.facebook.com/Champaigncountymastergardeners You do not need a Facebook account to view.
The losers most commonly reported were the large leafed hydrangeas such as 'Endless Summer'. Their leaves as well as their stems were killed. They should grow new stems from the roots so these will need a heavy prune to remove the dead stems. Cultivars such as 'Endless Summer' bloom on current season's growth so they should flower this year. Interestingly many people reported that the large white flowered 'Annabelle' hydrangea and her kin (Hydrangea arborescens) and Pee Gee Hydrangea (Hydrangea paniculata) suffered much less damage than the pink and blue flowered large leaf hydrangeas (Hydrangea macrophylla). It is probably a difference in species tolerance to frost.
The other commonly listed loser was butterfly bush. It did not die to the ground this winter, but I think mine just died to the ground from the freeze. It should send out stems from the roots to flower as usual.
In my yard the damaged plant that brought me to tears was my wisteria. It was covered in flower buds. My daydreams of wisteria blossoms dripping from my arbor turned to nightmares of withered wisteria cadavers draping a mausoleum. The plant is sure to live and it may have a few blooms, but nothing compared to its potential. It is a good thing gardeners are optimists or maybe just good at letting our attention move to the next blooming daydream.
The bottom line is most healthy plants have enough food reserves to leaf out again. Brown fried leaves will hang on and look ugly for several weeks unless you physically remove them. We won't know for another two weeks or so what stems were killed. If you just can't wait to find out, scratch stems with your thumb nail. Dead stems will be brown underneath the epidermis. Live stems will be green and have the ability to leaf out again. Dead stems can be removed by pruning down to buds on green stems. Don't give up on sad looking plants just because a freeze fractured their fates.
For a view away from your fried-leafed plants, head to the UI Horticulture Club's Flower Show this Saturday and Sunday at the UI Stock Pavilion. Nearby take in Krannert Art Museum's Petals and Paintings and Plant Biology Conservatory open house and plant sale.