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Archive for Thursday, March 31, 2005

As grass greens, weeds take root

March 31, 2005

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Although it is still early for most broadleaf weeds to be growing, soon it will be difficult to tell the difference between the pansy-filled flower bed and the dandelion-filled front yard.

Both will be a showstopping display of beautiful lemon-yellow blooms. As the grass slowly greens back to life, the weeds are not far behind.

Dandelions and clover are easy to identify but difficult to control. They are both perennial weeds that tend to revitalize every year during good growing conditions. Dandelions re-emerge from thick taproots, and clover from underground stolons. On top of that, both can reproduce from seeds generated from the characteristic showy flowers of spring. Because of the perennial nature of these weeds, physical removal such as hand-pulling is often ineffective. Mowing can temporarily remove the showy yellow or white blooms, but the plants will send up a new flower quickly. Once dandelions reach the white "puffball" stage, wind and mowing can scatter the seeds all over the neighborhood.

The best controls for these weeds are post-emergent broadleaf herbicides. The most effective product is Trimec. It is a common herbicide that contains a mixture of 2,4-D, MCPP and Dicamba. Together, they can knock out 90 percent of most broadleaf weeds in the home lawn. Always check the herbicide label to make sure the product you choose is safe to use where and how you wish to use it.

Do not mow the lawn for several days before and after the application. This will allow for maximum uptake and internal movement of the herbicide. Do not water for at least 24 hours after application, and do not treat if rain is expected within 24 hours. Avoid applying broadleaf herbicides when temperatures exceed 80 degrees and/or when winds exceed 5 mph to ensure safety to both turfgrasses and nearby broadleaf shrubs and flowers.

Wild garlic and wild onion are two closely related plants that have become weed problems in many home lawns and landscapes. Though wild garlic and wild onion look much alike, each has an odor that is common to its name -- wild garlic smells like garlic and wild onion smells like onion. These plants are perennials that also can reproduce by seeds and aerial bulbils. Bulbils form at the top of the stem and are oval and smooth. Wild garlic also reproduces by underground bulb offsets, but wild onion does not. Both species produce a clump of bright green plants that is unsightly in most home lawns.

Luckily, control recommendations are the same for both. Use 2,4-D; 2,4-D plus MCPP; or 2,4-D plus MCPP plus Dicamba (i.e. Trimec). The combination products are preferred. Spray these weeds during March or early April on a day that is at least 50 degrees. A second application during March of next year will probably be needed to achieve almost complete control.

Unfortunately, we do not have a good chemical control for a fifth weed: Star-of-Bethlehem. A study from North Carolina compared all common weed control materials. The best products were Coolpower (31.3 percent weed control) and Turflon Ester (23.8 percent). Coolpower is a commercial-only product, but Turflon Ester is available to both commercial and residential users.

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