Extension News

Ask the ISU Extension Experts

Note to media editors:

Got gardening questions? Contact the Iowa State University Extension Hortline at (515) 294-3108 (Monday-Friday; 10 a.m.-12 noon and 1-4:30 p.m.) or send an e-mail to hortline@iastate.edu. For more gardening information visit us at Yard and Garden Online at www.yardandgarden.extension.iastate.edu.


When is the best time to plant garden mums?
Garden mums (Chrysanthemum x morifolium) often don’t overwinter well in Iowa. Repeated freezing and thawing of the soil during the winter months can heave plants out of the ground and cause severe damage or even death.

Spring is the best time to plant garden mums in Iowa. Mums planted in spring survive the winter much better than those planted in fall. Spring planted mums have the opportunity to grow and establish themselves over a period of several months. Fall planted mums have little time to establish themselves before winter and are much more likely to be severely damaged or destroyed.

My spruce trees are losing some of their needles. Is this normal?
While the needles on spruce trees persist for several years, it’s normal for spruce and other evergreens to lose needles each fall. The oldest needles (those closest to the tree’s trunk) turn yellow or brown and drop to the ground. A typical branch on a spruce tree will have the current year’s growth at the end of the branch. Last year’s growth and the previous year’s growth will be located further down on the branch. Healthy spruce trees should always retain several years worth of green needles. However, the inside of a large spruce tree will be completely bare.

Environmental stresses, such as drought, can weaken trees and cause them to drop a larger than normal percentage of their needles. Rhizosphaera needle cast, a fungal disease, can also cause extensive needle loss.

Can I prune dogwood shrubs in fall?
Fall pruning of dogwoods and other deciduous shrubs is not recommended. Late winter or early spring (March or early April in Iowa) is the best time to prune shrubs that are grown primarily for their attractive foliage, fruit or bark. Late winter or early spring is also the best time to prune deciduous shrubs that bloom in summer on the current season’s growth. It’s best to prune spring-flowering shrubs, such as lilacs, immediately after flowering.


Contacts :

Richard Jauron , Horticulture, (515) 294-1871, rjauron@iastate.edu

Jean McGuire , Extension Communications and Marketing, (515) 294-7033, jmcguire@iastate.edu