Extension News

Ask the ISU Experts

Pinching back a mum

Note to media editors:

This column will be published each Wednesday during the growing season.

Got gardening questions? Contact the Hortline at (515) 294-3108 (M-F; 10-12 & 1-4:30) or e-mail us at hortline@iastate.edu.  For more gardening information visit us at Yard and Garden Online (www.yardandgarden.extension.iastate.edu)


This week's column was written this week by Iowa State University Extension horticulture, plant pathology and entomology specialists. The questions were chosen from those submitted by users of the ISU Hortline.

My chrysanthemums get tall and lanky and flop over onto the ground in the fall. What can be done to prevent this?
Pinch newly planted and established mums from spring to mid-summer. Remove the stem tips when the shoots are approximately 6 inches tall. New lateral (side) branches will develop along the stem on the remaining portion of the plant. As soon as these new shoots become 6 to 8 inches long, they should also be pinched. Pinching can be done with your fingers or a pair of hand shears. Continue pinching until early July. Pinching mums results in bushy, compact plants with additional flowers.

While pinching is helpful, tall upright mums may need staking or wire support hoops to prevent the stems from flopping over when laden with flowers. Wire rings and other plant supports are available at garden centers and other garden supply outlets.

When should I stop harvesting rhubarb?
Gardeners should stop harvesting well established rhubarb plants by mid-June. Continued harvest through the summer months weakens the rhubarb plants and reduces the yield and quality of next year’s crop. 

What part of the day is the best time to mow the lawn?
If possible, mow in the cool of the morning or evening. Mowing during high temperatures of mid-day places additional stress on the turf. Also, make sure the mower blade is sharp. Dull blades tear and bruise the leaf tips.

A few branches on my variegated Harlequin maple have green leaves. What should I do?
Occasionally, branches on the Harlequin maple (Acer platanoides ‘Drummondii’) do revert to the normal green-leaved type. To maintain the desired variegated foliage, any green-leaved branches should be pruned out as soon as they appear. The green-leaved branches are more vigorous than the variegated growth. If not pruned out, the solid green branches may become the dominant portion of the tree.

How do I control mosquitoes in my yard?
Mosquito control in a yard situation is difficult. The best way to prevent mosquito bites is to use an insect repellant containing DEET. There are a few things that you can do to reduce the number of mosquitoes in your yard. Make sure there is no standing water, mosquito larvae can develop in very small amounts of water.  Bird baths should have their water replaced every week to kill mosquito larvae.  Spraying bushes and other vegetation with insecticides may reduce the number of some mosquito species for a few days, but does not reduce the number of Culex mosquitoes (Culex mosquitoes are the primary vectors of West Nile Virus).


Contacts :

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

Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu

Pinching back a young mum

A pinched mum stem