What to do about weeds


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Despite the thick growth of this ground cover, one can observe the purple flowers of the weed Florida Betony. Hand removal will prevent further seeding.

Courtesy of David Holmes
Published: Saturday, May 1, 2010 at 6:01 a.m.
Last Modified: Wednesday, April 28, 2010 at 11:02 a.m.

While teaching a class for commercial pesticide applicators recently, I began with the observation that a weed is a plant out of place.

A few days later, when walking by a Florida Friendly landscape, I was reminded of this when I spotted a patch of mimosa vine. Although this plant appears in the University of Florida's book "Weeds of Southern Turfgrass," it is gaining popularity for bedding areas because it is drought tolerant, it spreads and it produces an interesting purple flower. In turf it is a weed, but in mass plantings, it can be a very desirable plant.

Weeds have various factors that influence when they appear. Some perform well in cool weather, while others are seen only during the hot summer season. Those weeds which grow in one season and develop seeds for next year are annual weeds - winter annuals or summer annuals.

Still other weeds are more permanent in nature, either with a two-year life cycle - biennials - or longer - perennials. Consider that trees are perennials as their life cycle is longer than one year. Could it be that trees that volunteer in plant beds where they are unwanted are actually perennial weeds?

As we think about weeds, control is usually the point of interest because in addition to their unkempt, unsightly appearance, weeds compete with desirable crops for nutrients, water and space. Moreover, weeds harbor pests and sometimes have toxins that are detrimental to landscape plants. Left unchecked, weeds produce vast amounts of seed that will make their appearance next spring in even greater numbers. The weed life cycle has four primary stages, emerging first as a seedling, which are small delicate plantlets emerging from seed; second vegetative, a period of fast growth, where stems and foliage are produced; third seed production, where the plant's energy is directed to the production of seed, and finally maturity, where seed ripens and the plant itself has little or no growth or movement of water and nutrients.

Given this background, summer annual weeds are beginning to emerge in plant beds as small delicate plantlets. As a strategy, it is important to realize that you always will have some weeds but the goal is to minimize the number you have. It is important to control those you have as early as possible, before they have a chance to steal nutrients and water from desirable plants and, with an eye toward next year, before they have a chance to flower and set seed.

Because chemicals are often the quickest and least laborious way to get rid of weeds, people often seek this first as a solution to weed problems. However chemicals are hard on the environment, they are expensive and there are limited choices for use by home gardeners. In reality, chemicals are often the last resort for weed control.

The simplest option for weed control is removal by hand, something that gives immediate gratification. This option also has drawbacks in that it is labor intensive, monotonous, in some cases all of the root must be removed or the weed may sprout back and stooping to weed can be hard on the body.

As these first two options are often unacceptable, a third possibility - cultural controls - presents itself as an attractive alternative.

In implementing cultural controls, first, try to cover as much of the bare ground as possible, either by growing the desirable plants thickly or covering any exposed areas with 2 inches of mulch to prevent opportunistic weed seeds from sprouting in bare soil.

In some cases, weed mat can be installed during the initial planting as a further guard against weeds. Next, scout for weeds and remove them as early as possible to insure they don't have a chance to root and, more importantly, seed.

Finally, be sure weeds are controlled in areas adjacent to the plant bed by conducting regular mowing or string trimming, so weed seeds don't have an opportunity to blow into the desirable bedded area.

As a gardener who often deals with weeds, I find myself thinking of a verse in scripture that declares "the poor you shall always have with you." It occurs to me that the same could be said of weeds. The secret to minimizing them is to scout for them often and to control them early.

David Holmes is Marion County extension director. Contact him at david.holmes@marioncountyfl.org.

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