Extension News

Ask the ISU Extension Gardening 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.


How deep should I plant my gladiolus bulbs? 

Planting depth varies with the size of the bulb (corm). Large corms should be planted 4 to 6 inches deep and 6 inches apart. Small corms should be planted at a depth of 3 inches. Gladioli require well-drained soils and perform best in a sunny location. Glads normally bloom about 8 to 10 weeks after planting. 


Which shrubs will grow in shade? 

Most deciduous shrubs perform best when grown in areas that receive partial to full sun. However, there are shrubs that can be successfully grown in partial shade. (Sites in partial shade receive two to four hours of direct sun.)


Deciduous shrubs that can be successfully grown in partial shade include; pagoda dogwood (Cornus alternifolia),  gray dogwood (Cornus racemosa), bush honeysuckle (Diervilla lonicera), fothergilla (Fothergilla spp.), common witchhazel (Hamamelis virginiana), smooth hydrangea (Hydrangea arborescens), Virginia sweetspire (Itea virginica), Japanese kerria (Kerria japonica), alpine currant (Ribes alpinum), arrowwood viburnum (Viburnum dentatum) and American cranberrybush viburnum (Viburnum trilobum). 


Yew (Taxus spp.), arborvitae (Thuja spp.) and Russian cypress (Microbiota decussata) are evergreen shrubs that can be grown in partial shade. 


What materials would be a good mulch for a vegetable garden?

Lawn clippings, straw and leaves are excellent mulches for the vegetable garden. Allow lawn clippings to dry before applying them to gardens. A thick layer of fresh lawn clippings may get hot and produce an unpleasant odor. If the lawn has been treated with a broadleaf herbicide, don’t use the clippings until the lawn has been mowed two or three times after the application.


Straw should be free of crop and weed seed. Suitable materials include wheat, oat and soybean straw. Leaves should be shredded or composted before applied as a mulch. Shredded or composted leaves are less likely to blow away in the wind.


A mulch depth of 2 to 4 inches would be appropriate when applying these materials to the vegetable garden.


My peonies bloom poorly.  What could be wrong? 

There are several factors which may cause peonies to bloom poorly. Peonies perform best in full sun. Peonies that receive less than 4 hours of direct sun will not bloom well. Plants growing in a shady location should be transplanted to a sunny site in September. Peonies planted too deeply often fail to bloom well. 


When planting peonies, position the peony buds 1 to 2 inches below the soil surface. Peonies that are planted too deeply produce lush foliage, but don’t bloom well. Recently planted or divided peonies may not bloom well for two or three years. The new plants need to grow and get stronger before they are capable of blooming well. Also, premature removal of peony foliage in July or August weakens plants, resulting in few flowers the following spring. 



Contacts :

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

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