Identification is important in weed management

Chad Gulley

What is a weed? A weed is described as “a plant that can cause economic loss in a production unit.” Many gardeners and home landscape managers view a weed as a “plant growing out of place.” Still others view a weed as a “plant whose virtue has yet to be discovered.”

Narrowing the weed species to an annual, perennial, biennial, etc. can help provide details on control options. It is extremely important for landowners to know the plants on their property so that you can know which plants are good and to identify invasive plants.

Plants can be identified by a number of factors. By looking at various plant parts, we can determine which family the weed belongs. For example, does the weed have a round, square or triangular stem? What is the leaf or leaflet pattern of the weed or plant in question look like? Flowers and fruit may also be distinguishing features. Some plants look very different when young and immature compared to older, mature plants.

What is a desirable plant to one person is a weed to another. For example, bermudagrass is a desirable grass in a lawn or pasture setting. However, in a flower bed, bermudagrass is a weed that many gardeners spend countless hours trying to control.

The best defense against a weed infestation is a dense stand of grass. Weeds are opportunistic, meaning they will grow and compete with the desirable plants as conditions allow. With proper nutrition and management, weeds may not compete with dense stands of grass or forage.

There are a number of useful websites, books and other resources out there to aid in weed identification. For aquatic weeds, this site is helpful: http://aquaplant.tamu.edu. For lawn weeds, this, too, is a helpful site: http://aggieturf.tamu.edu. A USDA site for plant identification is http://plants.usda.gov. For tree identification, http://texastreeid.tamu.edu is a good site. Another helpful site is http://noble.org/apps/plantimagegallery/index.aspx. If you have or suspect you have an invasive species, this site is helpful: http://texasinvasives.org. There are numerous sites and resources available.

Hand-pulling of some weed species is one method of control. The problem with this method, though, is with some weeds the growing points are below the surface and stays there when the weed breaks off when pulled. For example, nutsage, or nutgrass as some call it, is not truly a grass but, as the name implies, is a sedge. It has a triangular stem. On the roots are tiny nut-like structures, or tubers, that, unless removed from the soil, are where the future growth of the sedge continues.

Some cultural, mechanical and beneficial controls may be an option. Some plants respond to cultural changes, while others may have natural enemies that offer some control. Cultural changes may be preparing a seedbed, crop rotations, seed selection and other means of giving the desirable plant an opportunity to outcompete weed species. Mechanical controls include hoeing and plowing. Least toxic pesticides may be a tool in some instances when other controls are not working or the number of weeds may be causing economical losses to crops, forages, landscape plants, etc.

The growing season for the weed is important to know, as well. Some are winter annuals, summer annuals, perennials or biennial plants growing at various times, seasons and conditions. In many cases, as one weed goes out, another may begin to take its place. Winter annuals are germinating and growing now.

The Texas A&M AgriLife Extension Service in Smith County is glad to aid in the identification and control options for many weeds in your landscape, pasture or garden area. It is helpful to get a good close-up photo of identifying plant parts, including the leaf, stem, flowers and fruit or seeds. These photos may be emailed or brought to our office. A good sample of the actual weed pulled up is helpful as well.

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