Listed below are the most common lawn weeds and the recommended herbicide controls, as found in Utah State University Extension's publication titled "Landscape and Garden Weed Control". This publication may be viewed or downloaded from the website: http://extension.usu.edu/files/gardpubs/weedcont.htm
CRABGRASSDigitaria sanguinalis Crabgrass is an annual weed that reproduces from seed. If you can prevent seed development, you will, over time, reduce your crabgrass infestation.
To control crabgrass in the summer or fall, use a post-emergent type of crabgrass herbicide, such as those containing MSMA. Control is best on young plants. |
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BARNYARD GRASSEchinochloa crus-galli Barnyard grass is another annual grass weed that often takes advantage of bare ground. Like crabgrass, it is an annual and grows from seed every season. Eliminate the seed source and you will eventually eliminate the weed problem.
Control is similar to crabgrass. |
DANDELIONTaraxacum spp. Dandelion is a perennial weed that develops a h3 taproot. The 'look' of a dandelion plant can vary, but the flower is a dead give-away. Seeds can fly for great distances, and there will never be a shortage.
Control dandelion plants now with a broadleaf herbicide containing 2,4-D. This will help prevent them from overwintering in your lawn. |
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SPURGEEuphorbia spp. There are several different species of these mat-forming annual weeds. One very common species is identifiable by the purple spot on the small leaves. Milky sap is another identifying characteristic.
Control spurge by spraying with a broadleaf herbicide containing 2,4-D, MCPP, and dicamba, or an herbicide containing triclopyr and cloypralid. |
COMMON MALLOWMalva neglecta Common mallow can live as an annual, winter annual, or biennial. Young plants starting in late summer or fall will likely overwinter and get an early start next spring.
Control mallow by spraying with a broadleaf herbicide containing 2,4-D, MCPP, and dicamba, or an herbicide containing triclopyr and cloypralid. |
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GREEN FOXTAILSetaria viridis Green foxtail is a grassy weed that often goes unnoticed until it begins producing seed heads in July. Before that, it is only visible as a broad-bladed, lighter green grass growing in the lawn. It is an annual weed and will be well-controlled over time when prevented from setting seed.
The crabgrass killer type of herbicide, containing MSMA, is the best post-emergent control recommended. |
FIELD BINDWEEDConvolvulus arvensis Field bindweed is often called 'Morning Glory', and it is in the same botanical family as the ornamental annual Morning Glory. But this perennial weed is a serious pest year to year. It blooms white to light pink from late June through frost.
Field bindweed is hard to kill; it is better managed than eradicated. Perhaps the best 'control' for bindweed is a tough competitor. A vigorous lawn will usually out-compete bindweed. Thick mulch can also deter bindweed growth. In barren spots, the weed grows without bounds. In these areas, use an herbicide containing glyphosate or 2,4-D, and re-treat several times at 2 to 3 week intervals until freezing temperatures send this plant into dormancy. Next spring, try to get a handle on this weed as soon as possible |
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Prickly LettuceLactuca serriola A biennial or winter annual, prickly lettuce reproduces from seed. It is a native of Europe but is now naturalized throughout most of North America. Very common in any disturbed or bare soil. Flowers resemble dandelions and occur June - September. |
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Creeping woodsorrelOxalis corniculata Sometimes known as sheep's sorrel or sheep's sour, this is a perennial that will continue to creep year after year. Foliage may overwinter successfully. Flowers are small with 5 yellow petals, and flowering occurs throughout summer and fall. Seed pods are erect and when seeds are mature, the pod will explode and disperse the seeds widely. |
LambsquartersChenopodium berlandieri Lambsquarters is in the same genus as spinach, and the foliage is actually edible. Very common in disturbed soils. Lambsquarters is an alternate host for the beet leafhopper, which can transmit plant disease into sugar beets and tomatoes. |
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KnotweedPolygonum aviculare Annual that can grows prostrately along the ground. A close relative, P. erectum , looks the same but grows in a more erect habit. This weed seems to prefer dry, compacted soils. Small, inconspicuous flowers are located in the leaf axils in summer. |
FleabaneErigeron sp. In weedy areas, fleabane grows fairly short (<12") and blooms in early summer. It is an annual. |
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GoatsbeardTragopogon dubius Also known as Western salsify, this biennial weed disguises itself as a grass when young. The giant dandelion-like seed head follows a giant, dandelion-like flower that blooms in June or July. |