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Photo 6. Mouseear chickweed (Ceratstium vulgarum).
Prevention is a key management tool for this weed. Once established, it can be difficult to manage because it is very tolerant of low mowing heights and can produce seeds readily (see Photo 2). Annual bluegrass is drought susceptible, so deep watering less frequently will help discourage the growth of this weed. Preemergent herbicides like Betasan can help
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Photo 7. Bittercress (Cardamine hirsute).
prevent the establishment of the weed.
Broadleaf weeds are not sensitive to grass herbicides. They can be selectively controlled in many turf settings with herbicides that do not kill the grass. Mechanical control is often another effective way to help manage broad-leaved weeds. The growing point on annual broadleaf weeds is typically higher on the weed where it is easier to reach than with a grass (where it is often located very low). If annual broadleaves are cut below the two cotyledons that emerge from the seed, the plant will die. As long as this is done before seed is set, it is a very effective means of control. Broad-leaved perennials are more difficult to control, as they can spread through stem pieces, rhizomes or stolons in addition to seeds. Dandelion (Taraxacum officinale)
Nurs ery Views • Spri ng 2017
(Photo 3) is a perennial that has a deep taproot that can make management difficult because it will send up new shoots if the crown of the plant is cut. It also spreads readily by seed that is blown on the wind. Repeated digging can help control this plant if it establishes. Gallery is an effective pre-emergent, and 2,4-D post-emergent herbicides help manage this weed, but because it is so common and so easily spread by seed, management will be a yearly chore.
Horsenettle (Solanum carolinense) is an erect perennial weed most commonly found in dry sites. It spreads through seeds and rhizomes, so it is best to prevent this weed from establishing and to avoid
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cutting the rhizomes, which encourages spread. The plant is very spiny, which makes hand pulling painful, but horsenettle doesn’t tolerate mowing. If mowing does not provide satisfactory control, application of glyphosate can be used to provide additional control of the rhizomes.
Prickly lettuce (Lactuca serriola) is a winter or summer annual, or a biennial. The broad leaves and stems will leak a milky, sticky sap if cut, and there are sharp prickles on the back of leaf mid-rib. It is troublesome because a single plant can produce many wind-blown seeds that remain dormant for years in the soil. Cultivation and burndown post-emergent herbicides like Diquat are effective in managing this weed. Purple deadnettle (Lamium purpureum) and henbit (Lamium amplexicaule) are two winter annuals that are often confused with each other because they both are in the mint family, have square stems and similar flowers, and grow at the same time in the same areas. Purple deadnettle leaves (Photo 4) are triangular, and the leaves are clustered at the end of the stem, and they are usually distinctly purple at the top of the plant. Henbit leaves are whorled around the stem and are deeply lobed. A late-summer application of Gallery, a pre-emergent herbicide, is effective at killing these weeds but needs to be applied before the seeds germinate. Ground ivy (Glechoma hederacea), is a perennial that is can be confused with