Don’t let weed woes get you down

Daniel Gill, Bogren, Richard C.  |  9/29/2008 8:32:27 PM

Get It Growing For 10/03/08

By Dan Gill
LSU AgCenter Horticulturist

There are lots of reasons why we shouldn’t let weeds grow in our landscapes.

Weeds – particularly in flowerbeds, shrub plantings and ground covers – cause landscapes to look unattractive and neglected. Even if the lawn is nicely mowed and edged and everything else looks neat, weedy beds ruin the appearance of the landscape. Weeds in turfgrass diminish the even, uniform look we desire from our lawns.

Weeds also can be destructive when they compete with landscape plants for light, water and soil nutrients. Allow a weedy vine to grow over a shrub for several months and you will find that sections of the shrub have been shaded out and killed. And some weeds, if left unchecked, can outcompete turfgrass and damage the lawn, requiring repair work.

I frequently hear the comment, “It seems like this weed just suddenly became a major problem.” If we are honest with ourselves, however, we have to admit that weed problems do not happen overnight or in a matter of days or even a few weeks. Serious weed problems occur primarily when there is chronic neglect and when not enough effective effort is made to bring them under control.

When someone tells me, “I just can’t get rid of this weed,” I generally counter with, “Nothing can grow in your landscape unless you let it.” It’s mostly a matter of whether or not you are willing (or in some cases able) to put in the time, money and effort needed to do the job.

One clear truth is this – the more time and effort you put into managing a weed, the easier it gets. Over time, weed problems are greatly reduced in landscapes where weed control is done frequently and effectively.

Individuals who allow weed problems to get way out of hand before doing anything have a much harder time. People tend to put in a big effort at that point to clear things out. But if you sit back then and watch the weeds regain everything you worked so hard for, you will simply spin your wheels and make little real progress.

Staying on top of something rather than letting it go until it becomes a major problem is not an earth-shaking revelation. Still, it’s the best advice I can give you on weed control. The very best cure for weed problems is a liberal dose of regular attention.

That said, you also want to make sure that when you make an effort at weed control you are doing the most efficient and effective things. We employ two basic techniques in controlling weeds – physical and chemical. Both techniques include preventive and corrective methods.

Mulches (leaves, pine straw, newspaper and other materials) and landscape fabrics are preventive physical methods used in beds. These are applied to weeded areas to keep weeds from growing back. Hand weeding and hoeing are corrective physical controls done to deal with actively growing weeds.

There are some misconceptions about how mulches work. Mulch is not a literal barrier that keeps weeds from growing. The purpose of mulch is to block light from reaching the soil surface. Virtually all weed seeds need light to stimulate germination. When mulch blocks light from reaching the soil surface where the weed seeds are, they won’t sprout and grow. To accomplish this, the mulch needs to be thick enough – a depth of 2 inches is recommended. Mulches will not prevent weeds from growing up from bulbs or rhizomes.

Mulches applied to and maintained at the proper depth will help reduce problems (you will not get perfect control with any technique) with annual weeds that grow from seeds, such as chamber bitters (gripe weed), spurge, annual bluegrass and chickweed. Perennial weeds growing from rhizomes – such as Bermuda grass and torpedo grass – or bulbs – such as nutsedge or oxalis – will grow through mulch.

Landscape fabric or weed barrier fabric will do more to suppress these perennial weeds. But some, such as torpedo grass, can still punch their way through the fabric and grow. Landscape fabric is unattractive in beds and is generally covered with an organic mulch (pine bark, pine straw, etc.) to improve its appearance.

Once weeds are up and growing, hand weeding or hoeing does an excellent job of controlling weeds if you do it regularly – at least once a week. As long as you are not dealing with tough, perennial weeds, hand weeding combined with a 2-inch mulch will keep most beds attractive and not work you to death.

Usually, annual weeds simply can be pulled out (this is generally easier after watering or a rain). Weeds with bulbs or rhizomes must be dug up to remove the below-ground parts. Hoes cut off weeds at or just below the soil surface and generally work well on annual weeds. But perennial weeds will simply resprout from their below-ground parts, and that makes hoeing a poor control for them.

I’m just getting started, and I’ve already filled up my allotted space. I can see that this topic needs another column. Check out the next column, when I will continue to discuss weed control and focus on the use of herbicides and weed control in lawns.

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Contact: Dan Gill at (225) 578-2222 or dgill@agcenter.lsu.edu
Editor: Rick Bogren at (225) 578-5839 or rbogren@agcenter.lsu.edu

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