JoAnne Skelly: Weeds create dilemmas
April 4, 2017
My sister-in-law has a challenging weed dilemma. She lives in Arizona where they too had lots of rain this past winter. Because of this, the weeds in her yard are at least thigh-high after just a few weeks of growing.
When I was visiting two weeks ago, she was trying to decide the best way to handle the weeds. The options were weed whack them; spray them with a glyphosate (Roundup, Kleenup, etc.) or preemergent herbicide mix; or pull the weeds by hand.
Here are some factors influencing her decision. She needs almost two acres of their 10 acres of native landscape weeded, more if she wants better defensible space. That's a lot of weeding, mowing or spraying! Since the house is on the market, she needs to keep it looking good and hopes not to have to keep weeding over and over until the house sells. However, another concern is that she has an organic raised bed garden and she is averse to using inorganic herbicides, particularly since the garden is a selling point for the house.
In years past, she has hired someone to mow all the weeds periodically through the year with a weed whacker while she pulled the weeds around her trees and in her garden by hand. The only herbicide she has tried is corn gluten and it didn't work.
I told her that for a preemergent to work, it has to contact the soil and then be watered in or incorporated by raking, depending on the product. Weed whacking all those tall weeds would leave a heavy layer of mowed debris covering up everything he wanted to spray, including the soil.
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Now, her yardman wanted to first weed whack and then spray with a combination herbicide that would kill the weeds and also act as a preemergent preventing seeds from growing for eight months. Sounds good, but would it work? She asked my advice. I told her that for a preemergent to work, it has to contact the soil and then be watered in or incorporated by raking, depending on the product. Weed whacking all those tall weeds would leave a heavy layer of mowed debris covering up everything he wanted to spray, including the soil. That debris would have to be removed before any herbicide application. In addition, glyphosate products only work on actively growing tissue. While there might be some green stubble left after he cut down the weeds, it wouldn't be actively growing for a while and might not be enough to absorb the chemical for an effective kill. When she heard that it needed to be watered in, or raked in, she was really stymied.
Deciding how best to manage a large weed problem can be much more complicated than it might seem.
JoAnne Skelly is Associate Professor & Extension Educator, Emerita at University of Nevada Cooperative Extension. She can be reached at firstname.lastname@example.org.