Put Winter Weeds Under Control

Do you suffer from the ineffectiveness of your weed-management program. With upcoming warm days and other maintenance activities, you easily can forget about weed control. However, with appropriate action now, your weed problems will not come back to bother you.

The weed-control strategy you should use depends on the types of weeds present. Therefore, the first thing you need to do is determine the major weed species at each property you maintain. You may need to use different strategies at the different sites, based on the predominant weed species. For example, wild onion may be the only serious weed at one site, while another location has common chickweed and annual bluegrass as the predominate problems. These two sites would certainly require different treatments.

In some ways, it's easier to control winter weeds than summer weeds. However, if you neglect them, winter weeds can become a major burden in spring when you need to devote your time to other maintenance practices. Thus, treating for weeds now buys you time in the spring. And no matter what season it is, it is always easier to maintain a site in weed-free condition than it is to bring a heavily weeded site back into top condition. It pays to be proactive in your weed-control program.

Because we already have passed the peak period for winter-annual germination (which mostly occurs in December and January here in Phoenix), your weed-management activities right now will have to address both the control of existing weeds and residual control for weeds that will germinate later. I hope that you applied pre-emergents in the fall because winter annuals germinate in early fall, with little germination during the coldest winter months. However, a second flush of germination can occur in early spring as temperatures start to rise. This is why some operators use split applications of pre-emergence herbicides: to control both flushes of germination. A September application for controlling fall-germinating weeds may no longer be effective by March, when more germination can occur.

Classification of winter weeds Most winter weeds fall into two categories: grasses and broadleaves. Weeds such as yellow nutsedge-neither a grass nor a broadleaf-are not a concern in winter because these plants go dormant with the onset of cold weather in very late fall and do not emerge in spring until after temperatures have warmed up. Likewise, you cannot control warm-season grasses such as dallisgrass and bermudagrass in winter because these species also go dormant.

Broadleaf weeds consist of annuals, biennials and perennials. Examples of winter annuals include common chickweed, corn speedwell, vetches, rockets and henbit. Biennial weeds include certain thistles, such as musk thistle. Perennial winter broadleaves include bulbous buttercup and mouseear chickweed. In addition, seed of certain perennials that grow actively in warmer weather, such as dandelion and buckhorn plantain, often germinate in fall and early spring and therefore need attention in a fall weed-management program.

Grasses are either annual or perennial. Annual bluegrass is a common winter-annual weed. A perennial biotype of annual bluegrass exists, but this predominately is a golf-course problem. Quackgrass is a cool-season perennial grass that can invade turf and ornamental beds. If you maintain warm-season turf, you know that clumps of cool-season grasses such as tall fescue become quite apparent when the turf goes dormant. Cool-season grasses can be a conspicuous weed problem in such circumstances.

Other perennial monocot weeds (that are neither grasses nor broadleaves) of concern in fall and early spring include wild onion, wild garlic, grape hyacinth and star of Bethlehem. As in summer, perennial winter weeds are harder to control than annuals.

Weather conditions obviously are quite different in winter than summer, and this can impact weed management, especially herbicide applications. Temperature is an important factor for post-emergence herbicide application. Applicators frequently ask me about the minimum temperature in which they can apply post-emergents. This is not an easy question to address. I prefer air temperatures above 60 degrees Fahrenheit, with good soil moisture so weeds are actively growing. As temperatures drop, two effects occur. First, the development of injury symptoms is much slower compared to applications at higher temperatures. This does not necessarily mean that control ultimately will be worse. But if, for example, a herbicide takes 1 week in summer for effects to become visible, it may take 2 or 3 weeks in the winter. Thus, you may need to inform your clients not to expect fast results in the winter. Some weeds, such as henbit, seem to take an especially long time before complete control is apparent.

Or you can let Greens Keeper Landscape Maintenance do all the work for you and take the burden off your shoulders all together.  Give us a call at 623-848-8277 and let’s talk about it.

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Greens Keeper Landscape Maintenance, LLC
623-848-8277
http://www.commerciallandscapecare.com
greenskeeperllc@cox.net