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 do I control white clover in my lawn? 
White clover is a prominent plant in many Iowa lawns in late spring/early summer. White clover (Trifolium repens) is a creeping perennial. Plant stems root at the nodes where they touch the soil. The leaves are composed of three leaflets. Plants bloom profusely in late spring/early summer. Flower heads consist of 20 to 40 individual white to pinkish white, fragrant flowers. White clover is common in many lawns because it is a prolific seed producer and adapts well to mowing and other lawn care practices. Its presence is often a sign of low nitrogen fertility. 
White clover in lawns can be controlled through proper fertilization and the application of broadleaf herbicides. Late April/early May, September, and late October/early November are excellent times to fertilize Kentucky bluegrass lawns in Iowa. Products that contain 2,4-D, MCPP, dicamba or triclopyr provide good control of white clover. Applications of broadleaf herbicides in late spring/early summer provide some control of white clover. However, fall applications (late September to early November) are most effective. 

Will cucumbers cross-pollinate with other vine crops? 
Cucumbers will not cross-pollinate with squashes, pumpkins, muskmelons or watermelons. Cucumber varieties may cross with one another. However, the quality of this year’s crop is not affected. (An exception is the cross-pollination of parthenocarpic cucumber varieties with standard varieties.  Parthenocarpic varieties develop fruit without pollination. As a result, the non-fertilized fruit do not contain seeds. Parthenocarpic varieties must be isolated from standard varieties to prevent cross-pollination and seed development.) 

Should I deadhead my peonies? 
Remove the spent flowers (deadhead) to improve the peony plant’s appearance and prevent fruit formation. Fruit development reduces the amount of food the plant is able to store in its root system and may result in fewer flowers the following spring. 

Can tree peonies be successfully grown in Iowa?
Tree peonies (Paeonia suffruticosa) can be successfully grown in the state. Tree peonies perform best in partial to full sun. They require a well-drained, fertile soil. Many varieties are hardy to -25 degrees Fahrenheit. To ensure they survive the winter, encircle the plants with chicken wire or hardware cloth and fill the enclosure with straw, pine needles, or oak leaves in late fall. 

Tree peonies are actually small-sized shrubs. Plants seldom grow more than 4 to 5 feet tall.  Unlike garden peonies, tree peonies have woody stems that do not die back in the fall. Flowers may be single, semi-double or double and are commonly 6 to 8 inches wide. They are also available in a wide range of colors. Flower colors include white, pink and red. However, they are also available in the more unusual colors of yellow, purple and green. Tree peonies grow rather slowly. They often take four or more years to bloom well. 


Contacts :

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

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