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 should I cut back my ornamental grasses?
Many ornamental grasses provide color, motion and sound to the winter landscape. It’s best to cut back ornamental grasses in late winter/early spring before new growth begins to emerge. Cut the plants back to within 2 or 3 inches of the ground with a pruning shears or hedge shears. 

I planted some trees in late summer.  How long should I continue to water them?
While deciduous trees lose their leaves in fall and go dormant, their roots continue to grow until the ground freezes. Continue to water newly planted trees until the soil freezes in winter. Small trees usually require watering for one or two growing seasons. It may be necessary to water large trees for three or four years. 

Do I need to remove the leaves on my lawn? 
Turfgrass plants use light, water and nutrients to manufacture food. In fall, lawn areas beneath large trees are often completely covered with leaves. The leaf debris prevents the turfgrass plants from manufacturing and storing food prior to winter. A thick layer of leaves (little or no grass is visible) will need to be raked up and removed. It’s possible to deal with a thin layer of leaves (areas of grass are clearly visible) by chopping them up with a mulching mower. After mowing, little leaf debris should be visible. 

When should I apply a granular broadleaf herbicide to my lawn? 
Fall (mid-September through October) is the best time to control perennial broadleaf weeds in the lawn with broadleaf herbicides. In fall, perennial broadleaf weeds are transporting food (carbohydrates) from their foliage to their roots in preparation for winter. Broadleaf herbicides applied in fall will be absorbed by the broadleaf weed’s foliage and transported to the roots along with the carbohydrates, resulting in the destruction of the broadleaf weeds. 

Apply granular broadleaf herbicides and fertilizer/broadleaf herbicide combinations when the weed foliage is wet. Broadleaf herbicides are absorbed by the weed’s foliage, not its roots. To be effective, the granules must stick to the weeds and the herbicide absorbed by the weed’s foliage.  Apply granular products in the early morning when the foliage is wet with dew or irrigate the lawn prior to the application. 


Contacts :

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

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