Our Illinois weather may “play dirty" starting Friday night, especially in the northern part of the state. Predictions are for below freezing temperatures, which can damage or potentially kill vegetable seedlings, some fruit tree blossom, and tender or warm-loving transplants. Here are some tips to help keep plants safe:

• Covering those vegetable garden plants with an old bedsheet is usually enough. You also can cover individual transplants with plastic bags that easily go over the plant and with a bit of garden soil as a weight to secure it to the ground.
  • Don’t stress too much about your hardier veggies like cabbage, collards, leaf lettuce, peas, spinach, and turnips; they all should be able tolerate a light freeze.
  • However, frost-tolerant veggies – such as carrots, beets or radishes – may need a little protection as the temperatures are expected to drop below freezing.
  • Remember, tender veggies do not even like a frost, so keep that in mind these next few nights. Any cooler temps will slow them down or set them back. It can take 3-4 days for them to get back to actively growing again.
  • Not sure where your veggie plants fall on the scale? See a list of vegetables by category.
• Fruit trees vary in their susceptibility to winter cold injury. Apples typically are least likely damaged by winter or late spring frosts, while apricots and sweet cherries are most susceptible (primarily because of their very early bloom). Other stone fruits and pears are intermediate in their susceptibility to cold injury. Home fruit growers can cover the tree in any way they can. Smaller dwarf or semi dwarf trees are easier due to their reduced size. Can’t cover the whole tree? Consider covering just a few branches. The most susceptible to winter cold injury are apricot and sweet cherry; very susceptible: peaches and nectarines; moderately susceptible: plum, pear and sour cherry; least susceptible: apple. Read more on fruit trees in Illinois here.
• Lilac impact will depend on the variety and stage of development. Flower buds well on their way to opening could be damaged, while those with flower buds just starting to show or still tight will likely be safer. The smaller cultivars, such as Miss Kim or Dwarf Korean Lilac, are just now showing their tiny round flower buds. Since these are smaller plants it would be easier to cover them just in case.
• Rhubarb that has opened up from the crown also should be covered. If the leaves have not expanded much, you could cover with straw about 3 to 4 inches deep, or cover with a bushel basket or similar container, or several layers of newspaper.
• The same warning goes for annual and perennial flowers just planted. Cover them up, or if in containers, move them inside to the garage or three-season room for protection.

No one likes a cold snap in May, but it's always good to be prepared for handling it. We are in Illinois after all!

About the author: Richard Hentschel’s expertise extends across several subject areas with specialties in lawn care, fruit tree production, woody ornamentals, and home and community gardening. During his 45-year career in horticulture and agriculture, Hentschel became a well-known and respected expert for commercial and homeowner audiences, industry organizations, and media. He retired from University of Illinois Extension in April 2022 with nearly 30 years of service as a Horticulture Specialist and Educator in northern Illinois.