left over signs of the extreamlly harsh winter we just endured are still be see throughout central Iowa as many have noticed some trees, shrubs and perennials did not make it through the winter, this is especially true for roses and evergreens, even though the same plants have made it through all of the past previous winters included some trees that have been in place for 30 years or more. I did a little research to find out what was really the reason why there was such a significant loss, up to 25% of newly exotic to Iowa plant material has been lost has very slow growth this spring.

 

According to the United States Department of Agriculture All of Iowa is either zone 4 ( far north ) 5, or even 6 (far southeast ) These zones are further divided into sub zones. In central Iowa you are either listed in 5a which includes Boone, Ames, Marshalltown and Winterset, or zone 5b which encircles and includes the entire Des Moines metro. To be in zone 5b criteria temperatures cannot fall below -20.F, 5a -25.F. Last winter was the coldest in quite some time for Des Moines, but with research the lowest temperature reported at Des Moines International last winter was -14.F so that should not have been the reason why there was significant loss.

Upon future research I found the reason for the loss was the extent of the cold weather and the record frost depths levels that were reached as a result of the long lasting cold and low snowcover. It was made even worse by the fact that last fall was dry which took a toll on evergreens. At the garden center I work at I have heard of alot of death in evergreen shrubs and roses, especially knock out variety. I also have heard from some that some plants are still slow to grow which I can also vouch for, my switch grass is still barely coming up at this time.

So what are some things that can be done now that the damage has been done? Trees shrubs or perennials that have not come up by this time are likely not going to come up and should be removed and replaced. damaged trees and shrubs that had significant die back can have the branches pruned back to the point of growth, but be aware the structure of the tree or shrub could be damaged beyond repair and also keep in mind trees or shrubs that have been grafted may have died back below the graft union and could be totally different in color of leaves and blooms and different fruit on fruiting trees. When purchasing new shrubs be sure to pick them up from a local garden center as the nursery items sold here have the highest chances to be grown from northern stock which insures survival should this happen again.

Below is a list of plant material I’ve seen dead or damaged or has been reported dead or damaged.

Tulip Tree
Japanese Maple
Crab Apples
2013 planted trees
Knock out roses
Exotic Magnolias
Redbuds
Juniper
Rose of Sharron
White Pine
Red Pine
Yew
Spirea
Hydrangea Endless Summer