Extension News

Ask the ISU Extension Garden Experts: Weedy Strawberries, Forsythia and Lawn Mowing

Note to media editors: Got gardening questions? Call the Hortline at (515) 294-3108, Monday-Friday from 10 a.m. to noon and 1 to 4:30 p.m., or send an e-mail to hortline@iastate.edu. For more gardening information, visit us at Yard and Garden Online, http://www.yardandgarden.extension.iastate.edu.


How do I control weeds in my strawberry patch? 
Weed control is essential to insure optimal plant growth and fruit production. Weeds compete with the strawberry plants for water, nutrients and sunlight. Weeds also reduce air circulation and result in fruit and foliage staying wet for longer periods. Disease problems are more serious when plant tissue remains wet for long periods of time. 

Cultivation, hand pulling and mulching are the most practical weed control measures for home gardeners. Cultivate often, but shallow, to control weeds. Destroy the weeds before they have a chance to flower and produce seeds. Clean, weed-free straw and other organic materials can be applied as mulch between plant rows. Herbicides are not a viable option as few, if any, herbicides can be used on home strawberry plantings. 

Only the lower branches on my forsythia bloomed this spring.  Why? 
When selecting a forsythia, choose a variety (cultivar) that blooms reliably in Iowa. The flower buds on some varieties are not reliably cold hardy in Iowa. For example, the flower buds on ‘Lynwood Gold’ and ‘Spring Glory’ are hardy to -10 F. Since most parts of Iowa experience winter temperatures below -10 F, these cultivars often don’t bloom well in the state. Most likely you have a variety that is not reliably cold hardy in Iowa. The lower branches bloomed because they were covered with snow and protected from the cold winter temperatures. 

Excellent forsythia varieties for Iowa include ‘Meadowlark’ (8 to 10 foot tall), ‘Northern Sun’ (8 to 10 foot tall) and ‘Sunrise’ (5 to 6 foot tall). All three varieties possess excellent flower bud hardiness and bloom reliably in Iowa. 

How often should I mow my lawn? 
Kentucky bluegrass lawns should be mowed at a height of 2 ½ to 3 inches in the spring and fall months. Set the mower blade to a height of 3 to 3 ½ inches during summer. 

As a general rule, never remove more than one-third of the total leaf surface at any one mowing. For example, to maintain a lawn at three inches, the grass should be mowed when it reaches a height of four and one-half inches. Shorter mowing heights require more frequent mowing. 

Mowing frequency is largely determined by the growth rate of the turfgrass. Weather conditions, cultural practices (such as fertilization and irrigation practices) and other factors determine the growth rate of turfgrass. 

Kentucky bluegrass and other cool-season grasses grow quickly in spring when weather conditions are favorable. The growth of cool-season grasses slows in summer and then picks up again in fall. Fertilizing and irrigating the lawn on a regular basis promote turfgrass growth. 

In spring it may be necessary to mow every four or five days. Once every one to two weeks may be sufficient in summer (if the lawn isn’t irrigated), with more frequent mowing again in the fall.

Contacts :

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

Willy Klein, Extension Communications and External Relations, 515-294-0662, wklein@iastate.edu