Homegrown: Tips for winter plant care

Linn County Master Gardener, Lisa Slattery, provided the following timely tips on winter care for trees and other plants:

We've had a pretty easy winter so far here in Eastern Iowa.  We haven't seen many heavy, wet snows like the ones that can damage shrubs and take down trees.  But winter isn't over yet.  Big wet snows can wreak havoc on your shrubs and trees…even though your perennials are happily sleeping under all that free mulch! Other winter warlocks are extreme cold temperatures and deicing salts.  There are a few things you can do to help your landscape plants survive what's left of winter.

When we do get heavy snows, gently remove snow as it accumulates on small trees, evergreens and shrubs; shaking it off with a broom works well.  If you have smaller shrubs lining your driveway or walkways, make sure not to throw heavy snow on top of them when shoveling.  However, it's OK to keep small shrubs like evergreens covered with snow that falls on them – it protects them by acting as an insulating blanket against harsh winter winds that can dry out and desiccate the foliage.  

It's tougher to protect plants against extreme cold temperatures than to protect them against heavy snows.  For small shrubs, use chicken wire or burlap to encircle small shrubs and fill in with straw, pine needles or mulch.  For large shrubs and trees your only option is to choose trees and shrubs that are hardy for our area and will more easily withstand winter temperatures.  In Eastern Iowa we are zone 4 and 5 which means the average annual minimum temperature is -20 to -30 degrees Fahrenheit for zone 4 and -10 to -20 degrees Fahrenheit for zone 5.  According to ISU Extension, the dividing line between zone 4 and 5 runs across the State from approximately Council Bluffs to Ames to Dubuque.  Here in Linn County you're better off choosing plants that are reliably winter hardy for zone 4.  ISU Extension has a publication on deciduous shrubs available for a small fee on their website www.extension.iastate.edu/store/.  This lists more than 75 deciduous shrubs (organized by height, including photos) which would be a good source when choosing shrubs.

Winter salt damage can be minimized by using deicing salts sparingly.  Try to remove as much snow and ice as possible before applying and mix them with sand when possible.  ISU recommends fifty pounds of sand to 1 pound of salt.  If you have trees and shrubs near roadways that receive a lot of salt throughout the winter, flush the area with a thorough soaking of water as the ground thaws in spring. This helps to flush the salt from the root zone of your plants.  Salt-tolerant tree species can also be planted along streets. Linn County Master Gardener, Lisa Slattery.