Temperatures Going 60 to 20...What Happens to our Trees, Flowers and Bugs? - U of I Extension

News Release

Temperatures Going 60 to 20...What Happens to our Trees, Flowers and Bugs?

FOR IMMEDIATE RELEASE

March 23, 2017

You walk out of your home ready for the day, the sun hits your face, and it is an unusually warm day for February. You rejoice. Spring is here. The next day there is a light, fluffy snow hitting you in the eye. For most Illinoisans, we have become used to getting our hopes up, only to realize winter is not quite done with us yet. University of Illinois Horticulture Educator, Kelly Allsup, would like to help you answer a few questions on what this exactly means for nature around us.

What does this mean for the plants in our garden? Our trees? Horticulture educator Chris Enroth said, "Plants during the winter are dormant, slowing or suspending their processes. Warm temperatures may or may not trigger plants to wake from their winter slumber." Enroth said "chilling requirements" are a key factor.

"Over the eons, plants have encountered warm winter weather, triggering growth, which then is killed off when the winter weather returns," he said. "To counter the issue, many of our plants developed a chilling requirement. Chilling requirements, often measured in hours, are a period of time during which the plant must be exposed to cold weather (typically below 45 degrees Fahrenheit) to bring the plant out of dormancy."

Fruit trees such as apples have more chilling requirements than that of a peach tree. Most flowering trees require 500 to 2,000 chilling hours. If the trees have reached their chilling hours, warmer temperatures along with longer day length may cause buds to break and growth to occur earlier than usual. If we were then to get another hard frost, opening buds and young fruit could be extremely susceptible. As of March 14, we are around 900-1000 chilling hours, according to the Midwest Regional Climate Center.

The warmer temperatures also will increase the incidence of frost cracking. These longitudinal openings can extend deep into the wood of the tree and noticeable in the spring. This condition shows up in sycamores, maples, apples, cherries, horse chestnuts, lindens, walnuts, and willows. Frost cracks happen when sunlight warms the bark and inner wood on the south or west side. The bark and inner wood contract at different speeds when temperatures start to lower, causing the bark to split.

Frost cracking may occur because of too much pruning, which causes more sunlight to hit the bark, or if you removed a neighboring tree that helped shad it for many years. There is not much a homeowner can do fix frost cracks other than keeping the tree healthy.

Here are just a few insights from horticulturists to remember during this Illinois late winter/early spring:

  • Do not remove debris or mulch too soon as part of spring cleanup. It is a common practice to mulch in the winter to prevent frost heaving of perennials. When the plants are heaved, this exposes plant crowns to cold weather. If the temperatures were to drop too low, this would be an issue with whether the plant survives our winter or not.
  • Warmer temperatures may shorten the flowering time of bulbs. Cooler springs extend the lives of our favorite bulbs, but if it remains too warm, they will not last long. If it frosts after they have sent up a bud, they may not flower at all. However, early flowering would not affect overall bulb health, and it will bloom the following spring.
  • Warmer temperatures allow more spores and structures of diseases to survive in debris and litter. Warmer temperatures are more suitable for pathogen growth and reproductions and may cause an expansion of the disease range. The epidemics may be more severe and occur earlier than usual. Be on the lookout for disease if we remain wet and warm.
  • Cold temperatures help maintain normal plant cycles. According to horticulture educator Chris Enroth, "If your apple tree in the backyard requires 1,000 chilling hours, it is a safe bet these warm temperatures are not going to be enough to trigger growth. However, if your peach tree (a notably more southern crop) has a chilling requirement of 400 hours, you may want to invest in some winter protection for the possible emergence of flowers."
  • The upside to warmer winters is that the root zones always remained warmer overall. Warmer root zones have linked to heavier flower production, but they may also be more sporadic.
  • As for bugs, Horticulture educator Richard Hentschel said, "because cold temperatures arrived late, more bugs had the chance to find a spot to hibernate for the winter, and that often was around people's houses. The warmer temperatures caused bugs to come out of dormancy and search for warm spots, which happen to also be inside people's homes."University of Illinois Extension provides equal opportunities in program and employment. If you need a reasonable accommodation to attend any of our events please call (618) 344-4230. If you have a lawn or gardening questions you may call University of Illinois Extension and speak to a master gardener. They are available 9:00 a.m. – noon, Monday through Friday at 344-4230 or 939-3434.

Source: Kelly Allsup, Extension Educator, Horticulture, kallsup@illinois.edu

Pull date: May 1, 2017