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Index : Plant Care
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- 9. How to Control Bumper Crop of Weeds - Top
Home gardeners are having fits trying to control a bumper crop of weeds brought about by all our Winter rain. Landscapes and gardens are choked with unwanted growth, and the weeds just keep coming. To control them, it’s best to use a combination of mechanical and chemical measures.
First and foremost, it’s critical to kill the weeds before they become mature enough to produce seed. One small weed plant can literally produce hundreds of seed that can later sprout and grow. If the weeds haven’t matured, the best mechanical means of control is to cut them off with a hoe. If your weeding areas of rock-mulched landscape the best type of hoe to use is the Action Hoe, also called a ‘Hula’ Hoe. It has a triangular-shaped blade with a flat cutting bar that can be pushed under the rock mulch to slice through weeds but leave the gravel in place.
When using a hoe of any type, in the garden or landscape, try to shave off weeds at the soil line rather than slicing into the soil. Many landscape plants and most flowers and vegetables are shallow-rooted. Cutting into the soil damages these fine, shallow roots.
If weeds are mature and have seed ready to drop, it’s best to hand-pull or cut them off to prevent the seed from falling. Have a plastic bag on hand to stuff the seed laden weeds into. For the taller growing weeds, it will be easier to cut them off at ground level. Most weeds that sprouted up this winter were annual varieties, which means they won’t grow back from the roots.
As we’re now heading into the normally dry spring months, weed seeds will not have the moisture needed to continue sprouting and growing. However, when rains return this summer so will the weeds, unless weed control products are used to prevent their return.
Chemical weed preventers, also called pre-emergent herbicides, can be applied prior to the Monsoon season to prevent weed seeds from germinating. As our Summer rains usually begin in late June or early July, the time to apply these pre-emergent chemicals in mid-June.
Look for weed control products with labels like: Weed Stopper, Weed and Grass Preventer, or Weed Preventer on your garden center shelf. The chemicals, listed as the active ingredients in these products will be Surflan, sold as a liquid, or Amaze sold as a granular bagged product. They’re the two most widely used pre-emergent (before weeds emerge) chemicals. They can be purchased at most places garden products are sold. When applying pre-emergent herbicides it’s important to follow a few simple steps to insure their effectiveness.
To provide an adequate barrier to block the growth of weed seeds, these weed blocker chemicals need to be watered into the top layer of soil. If allowed to lay on the soil surface, even for a few days, these chemicals will volatilize into the air and loose there effectiveness.
The watering in is a simple process. After applying pre-emergent herbicide over open areas in the landscape, set some straight-sided cans randomly throughout the treated area. Use a fan-type portable lawn sprinkler to water the area. Leave the sprinkler on long enough to apply one-half inch of water. You can use the cans to measure the depth of water applied. When all of the cans have filled with one-half inch of water, the herbicide has been sufficiently soaked in.
Remember that the pre-emergent herbicide creates a chemical barrier in the soil to prevent weed seedlings from growing. If you break this chemical barrier by hoeing, pulling weeds, planting or otherwise disturbing the soil it will break this chemical barrier. In most cases the herbicide barrier will provide weed control through the Monsoon Season.
Finally, sprays are available to kill existing weeds. Among the most popular is the weed killer - Glyphosate. It comes in premixed and concentrate forms and can be used to kill perennial weeds, such as Witches Broom, Sandbur and Bindweed, roots and all so they won’t grow back. It can be used anytime weeds are actively growing. When in doubt whether a existing weed is an annual or perennial, and you want to use a spray control, use glyphosate
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161. - Updated: March 20, 2005
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