PPDL Picture of the Week

February 27, 2017

Warm Weather May Cause Problems for Ornamentals

Kyle Daniel, Nursery and Landscape Outreach Specialist, Horticulture and Landscape Architecture

The last few days, and coming week, temperatures across Indiana and the Midwest are abnormally high for February.  The southern part of the state should expect temperatures in the 70’s, while the northern parts are expecting upper 60’s.  Though the temperatures are a welcome reprieve from a ‘typical’ winter for us, most plants can have serious problems due to breaking bud too early.  Most of Indiana has accumulated greater than 900 chilling hours, which fulfills dormancy requirements for most ornamentals.  Temperatures play a key role in de-acclimation from dormancy in the spring.  When an extended time of warm temperatures occur, and chilling hours have been met, bud break begins to occur, as well as phloem begins to move within the vascular tissue.  If temperatures cool, the bud swell can be suspended, but it appears the long term forecast calls for temperatures around 50 for most of the state.  When bud break occurs followed by cold temperatures injury can occur, such as bud kill.  Since phloem may be active, bark splitting or cracking may also occur on thin barked trees if a cold period occurs after extended warm temperatures.  At this point it is too early to determine whether any damage will occur, but you should be inspecting plants as bud break occurs.  Damage may not be visible on the outside of the plants, but necrotic (dead/dying) tissue will be evident in the vascular tissue. Pruning out dead branches of trees and shrubs may be required this spring after damage has been assessed.


If you have any questions, please contact Kyle at daniel38@purdue.edu.

​Click image to enlarge


Figure 1.  Elm buds beginning to swell due to warm temperatures.


Figure 2.  Tulip Bulbs beginning to emerege, especially in dark mulch, due to the warming soil temperatures.