One of the most common homeowner questions that come into Extension offices across the state involves how to control broadleaf weeds in lawns. Dandelion growth season spurs the phone calls, and if you are troubled like me by the allergic reactions they cause, with good reason. The trouble with these and other broadleaf invaders is that many of the chemical controls that destroy them also can harm desirable plants on your property, most notably roses, shrubbery and many garden plants like tomatoes.

First, let’s take a few moments to review our science courses from our school days. Monocots and dicots are words that you probably don’t use sitting around the breakfast table, but they hold the key to understanding what will kill a plant and what will not harm them. The number of cotyledons found in the embryo is the actual basis for distinguishing the two classes of angiosperms and is the source of the names Monocotyledonae (one cotyledon) and Dicotyledonae (two cotyledons). The cotyledons are the seed leaves produced by the embryo. They serve to absorb nutrients packaged in the seed until the seedling is able to produce its first true leaves and begin photosynthesis. Grasses are monocotyledons.  They have straight veins in their narrow leaves and a fibrous root system. Corn, both a grain and a grass, is an example of a large monocot. Broadleaf weeds like dandelions are dicotyledons. As their name would indicate, they have wide leaves with branched vein systems. Other dicots around the house might include beans, boxwoods, roses and oak trees.

Broadleaves are opportunistic; they thrive on light and warmth for the most part. When lawns are left with barren spots or the grass in the lawn in mown to short heights of less than three inches, the light that is allowed to penetrate to the ground helps these weeds take hold. I noticed this in comparing my own lawn where grass that was mowed with one mower was about one inch shorter than the adjoining property we mow at a higher level. The lawn with the additional height after mowing had significantly fewer dandelion shoots at the following week’s mowing. When I adjusted my mower by raising the blade one inch in cutting height, the weed pressure dropped noticeably.

If broadleaf weeds are an issue in your home’s lawn, I encourage you to try this before applying the first drop of chemical control. Try moving your mower up one or two settings and see if you can see a reduction in weeds within the next few weeks of mowing. The additional shading of the taller grass and the reduction of clippings should produce a thicker, greener, and cleaner lawn. You may also find that by lowering the temperature of the ground, you get less crabgrass this fall as well. One can only hope.  Good luck and, as always, if you have a problem in your lawn or on your farm, the Extension office offers research-based, unbiased and free information and advice to help you combat the issue.

Upcoming Events

May--Smyth Washington Cattleman’s Meeting, date to be determined.

May 7--Bristol Steer Show Weigh In.

May 8--75th annual Bristol Steer Show.

May 15--VESA Meeting, Petersburg.

May 15-17--Tennessee State Ag Agent Meeting, Knoxville.

May 20--Marion Tree Commission Arbor Day Celebration, Marion Elementary School.

May 27--VFW Memorial Day Parade and Celebration, Marion.

June 17-21--Smyth County 4-H Camp.

June 21--Deadline to Consign Calves to July 17 VQA Sale.

June 24-27--Kentucky State Ag Agents Meeting, Owensboro.

July 17--VQA Sale, 7 p.m., Tri State Livestock Market.

July 19--Deadline to Consign Calves to August VQA Sale.

July 22--VQA Steer Take Up.

July 24--VQA Heifer Take Up.

July 29-30--Rich Valley Fair Livestock Shows.

Aug 21--VQA Sale.

Aug 22--Forage Field Day at Glade Research Farm.


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Dr. Andy Overbay is Smyth County’s agriculture and natural resources extension agent.

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