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Garden Variety: Controlling early spring weeds

April 3, 2014

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Two specific weeds seem to become nemeses to gardeners first in the growing season: dandelion and henbit. Both, in quantity, produce lush purple or yellow casts to open fields and, at the same, a singular eyesore in our space.

Dandelion

The recommended control for dandelions is in the fall. But if you missed the fall application, a second opportunity for dandelion control is approaching.

Dandelion seeds blow in the wind.

Dandelion seeds blow in the wind.

Research by Purdue University has shown that good control can be achieved with an herbicide applied during or soon after the first flush of flowers. Flowers that reach maturity produce air-born seeds, increasing their production.

Use a combination product that contains 2,4-D, MCPP and dicamba. Examples include products such as Trimec, Weed Out, Weed-B-Gon and Weed Free Zone. If you only have a few dandelions, consider spot treatment rather than a blanket application.

Some ornamental plants are sensitive to drift from these herbicides, so be careful. Avoid spraying on windy days. The three indicator plants that usually are the first to show damage are tomato, grape and eastern redbud trees.

Henbit

The plants with the little purple flowers that are starting to make themselves known in home lawns are called henbit. If you are not sure this is what you have, check the stems. If they are square rather than round, you have henbit. Though it actually comes up in the fall, most people do not pay much attention to this weed until it starts to flower.

Henbit flowers

Henbit flowers

Trying to kill it at this late stage with an herbicide is usually a waste of time and money. Though the plant may be burned back, it will rarely be killed. This is a winter annual; it comes up in the fall, matures in the spring and dies as soon as it starts to get hot. All that we can do now is keep it mowed until nature takes its course.

But we can do something next fall that will help next spring. Henbit usually germinates around mid-October. Spraying with 2,4-D, Weed-B-Gon, Weed Free Zone, Weed Out or Trimec in early November can go a long way toward eliminating henbit next spring. The plants are small during the fall and relatively easy to control.

Choose a day that is at least 50 degrees so the henbit is actively growing and will take up the chemical. Spot treating will probably be needed in the spring to catch the few plants that germinate late.

A strong, healthy lawn (or other ground cover) remains your best bet for controlling weeds of any kind. To this end, fertilization now is not recommended as it only produces an abundance of top growth, requiring both water and mowing with little beneficial root growth. Fall is best for lawn development.

— Stan Ring is the Horticulture Program Assistant for K-State Research and Extension in Douglas County. Extension Master Gardeners can help with your gardening questions at 843-7058 or mastergardener@douglas-county.com.

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