Weedy grasses and broadleaf weeds are further divided into groups according to the plants’ length of life. Perennial weeds have a life of more than two years, though new seeds may be produced every year. Biennial weeds have a life of two years, generally storing up food reserves in the leaves and roots the first year and producing seed in the second year. The biennial weeds often are grouped with perennial weeds since control is similar. Annual weeds germinate from seed, grow, flower, and produce seed in less than one year. Summer annuals germinate in the spring and mature in the fall, whereas winter annuals germinate in fall or late winter and mature in late spring.

Effective control of weeds in turf is based on correct identification. Many books and charts are available to help in identifying common lawn weeds. For additional help in weed identification, inquire at your county extension service.

Dandelion bloom usually peaks in early May. Bob Mugaas

Early May is usually when we see peak dandelion bloom.  This often causes people to run out and buy some form of a weed control product to kill them off.  However, the real preferred time to kill dandelions is in the fall of the year when the plant is moving food down to the root system to be stored over winter.  Nonetheless, there are many available products to kill dandelions even in the very active growth of spring.   Be sure to choose a product that is labeled for dandelion control in lawns.  Do not use products that are designed to kill all vegetation as they will kill the lawns grasses as well as the dandelions.

Weed and feed products designed to apply fertilizer as well as put down a broadleaf weed control product can be effective.  However, where there are only a few scattered broadleaf weeds such as dandelions in the lawn you will be applying a lot more product to the lawn than is necessary or effective.  You must get the product onto the dandelion foliage as these products do nothing to prevent new dandelions from emerging that start from seed.  Thus, if there are only a few scattered dandelions in the lawn, using a pre-mixed, ready-to-use product to spray onto the dandelion foliage is much more efficient and effective.  This strategy also introduces far less herbicide into the environment thereby reducing potential pollution and exposure problems.

Bob Mugaas, University of Minnesota Extension Educator

Crabgrass-Common Weeds of the United States

Crabgrass is a recurring problem in many home lawns, but it need not be. Crabgrass is a warm-season annual grass. Our lawns are composed of cool-season perennial grasses. Providing the right environment for desirable grasses to flourish deprives crabgrass of its best environment.

To keep lawns thick and healthy so there’s little space for crabgrass seed to sprout, you should:

 
• Mow frequently, removing only 1/3 of the blade length each time.
• Set the mower high: 2½” to 3″ during the hottest part of the summer.
• Water consistently and thoroughly throughout the growing season, if possible. Apply enough water to bring the weekly total to one to one and a half inches of rain and irrigation water combined.
• Fertilize more heavily in fall than spring.
• Aerate the lawn in early fall as soon as temperatures cool, if soil is compacted or clay-like.

 

 

When crabgrass is thick and unsightly in late summer, use a de-thatching rake or a power rake to remove most of it. This prepares the ground for overseeding which can take place between mid-August and mid-September in Minnesota.

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