Submitted by Steve Geist, Swingle Plant Pathologist
The recent record setting freezing temperatures will impact your landscape. On April 9 the low temperature plunged to 9 degrees after a record daytime low high temperature of 22. The low temperature of 6 degrees on April 10 also broke the previous record of 7 degrees. Northeast Colorado received varying amounts of snow. In some locations snow covered the ground providing some insulation while in other places the soil was bare.
Cold temperatures in and of themselves will not injure the lawn. Injury occurs when there is frost on the grass blades and the lawn is walked on. Grass blades break resulting in brown footprint patterns. This injury is short lived, but unsightly. Injury can be averted by staying off the lawn till the frost melts later in the day.
Exposed annuals and perennials may have been killed or severely damage. Some plants are cold hardy to 15 degrees F. However we experienced temperatures as low as 6 degrees at the Denver reporting station. In some instances, warm soils and snow cover may have insulated plant material.
Trees and Shrubs
Many shrubs already leafed out when the freeze occurred. Fruit trees had already leafed out as well. The leaves formed this spring will soon wither, turn black and fall. Some expanded buds look to also have frozen.
This year’s shoot growth may also have frozen. Primarily this applies to fruit trees.
Flower buds are more sensitive to the cold than leaf buds. Trees and shrubs that normally flower and produce fruit in the spring may not do so this year. If the flower buds are frozen they will not be replaced until 2014.
What will happen next?
The good news is most trees and shrubs will leaf back out later in the spring. There could be some twig dieback on succulent growth.
What to do:
• Some early flower displays may require replacement.
• Wait and see is the strategy on your trees and shrubs. Most of your “woody” plants will leaf back out over the next two – four weeks. Don’t be in a hurry to prune recently freeze-damaged twigs. If they are still pliable, give them a chance and prune the bare shoots in June.
• Watering, fertilizing and insect control should be completed as usual.
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