Ag Biz News Column
County Extension Agent—Ag/NR
Cool season weeds or what many just call “winter weeds” are in many lawns right now. These weeds include dandelions, chickweed, henbit, burweed, and clovers. Depending on the weed species, the weed will germinate in the fall, grow all winter, and produce seed then die in late spring as our warm season grasses begin to germinate. Controlling these weeds helps our turfgrass develop a dense, uniform cover as well allowing our grasses more access to water and nutrients.
Many weeds we deal with are herbaceous plants. Others are classified as forbs, grasses, sedges, and brushy weeds to name a few. Weeds may be annuals, living less than one year, or perennials that live for many years. Some germinate in the fall, over-winter in a rosette stage and go through stem elongation and flowering in the spring. This type of plant is considered to be a cool season annual. Warm season annual weeds will germinate from seed in the spring, go through stem elongation during the latter part of the spring and early summer, begin flowering in early to late summer, and then die by the fall or winter months. Biennial plants take two growing seasons to complete their life cycle. These factors are important when determining their value and management.
Annual weeds are easily controlled when they are young. Perennial weeds are typically controlled in the flowering or reproductive stage. Biennial plants are easily controlled in the rosette stage.
Dandelions (Taraxacum officinale) are a troublesome weed in many home lawns. Dandelions produce a bright, yellow flower. It can have a thick, deep taproot. A rosette of basal leaves emerge from the crown of the plant. The leaves are long, narrow and are deeply notched with backward pointed lobes. The leaves and stem contain a milk-like juice.
Chickweed or common chickweed (Stellaria media) is a matted, herbaceous, winter annual broadleaf plant. Chickweed develops prostrate, tender, freely branching stems that root at nodes. Chickweed has opposite, smooth, oval leaves with long petioles on the lower leaves and the upper leaves are sessile. It also has a shallow, fibrous and very frail root system. The flowers are solitary or in small clusters at the end of the stems with white petals.
Henbit (Lamium amplexicaule) is also a cool season annual weed. Henbit is a member of the mint family thus the characteristic square stem. The stems are slender, ascending or prostrate and are freely branched at the base. Stems may root at the lower nodes. Leaves are opposite, nearly circular with deep veins, hairy and are petioled. The upper leaves clasp the stem and lower leaves are distinctly petioled. The roots are shallow and fibrous. The flowers are tubular, pink to purple in color, and borne in the leaf axile.
Burweed otherwise known as “lawn burweed” or “carpet burweed” is another cool season annual and is a nuisance to golf courses, athletic fields, and home lawns across Texas and the Southwest. The sharp pointed spines on the seeds can easily pierce the skin. Burweed is a small, low-growing plant. In sites that have not been mowed, it only reaches about 2 inches in height and the individual plants may spread out to about 6 inches in diameter. Leaves are pinnately divided giving the plant a feathery appearance. Populations of this weed can become so high the plant covers the ground like a carpet.
Several species of clover can be troublesome in turfgrass as they compete with the grass in the home lawn in early spring. While it may be desirable to have white clovers in pastures and rangelands, Burclover is an annual plant with little forage value. White clover also called “Dutch clover” is a perennial mat-forming herbaceous plant with a creeping stem that roots at the nodes. Leaves are trifoliate with long, erect petioles. Leaflets are widely elliptic with toothed margins and usually with a white splotch near the base of the upper surface. Blooms are spherical cluster of white or pinkish flower developing from a long stalk. Burclover has similar characteristics to white clover except where the white clover has a distinctive white splotch on the upper leaf surface; burclover has either purplish markings or no distinctive markings. Flowers of burclover are yellow in small clusters.
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