Time to control your weeds


September 30, 2004


Victoria County Master Gardener


Now that seasons are about to change- and all your work has produced bud and bloom throughout the summer and into these transitional weeks - you will be able to relax. Well, not soo quickly. Everything is growing well and if it looks good to you, think how good it looks to the insects, birds and squirrels: "Lunch is served!"


Assuming that you followed most of the rules about bed preparation and fertilization, your lawn and gardens should be in fine condition. To keep them that way, you must do a regular patrol about the grounds to watch for diseases, insects and weeds. No matter how much care you have put into your gardening, weeds will find a way to come out and challenge you! By the wind, birds, animals and even in the root ball of new plants, weeds will come in and attempt to invade.


Some seeds previously dormant in your garden for several decades can come up when just the right conditions develop. So what provoked them to come up now? Those right conditions could have been the extra rain we received this summer, light or heavy tilling of the soil that could bring up seeds buried for decades, or weakening of turfgrass allowing, sunlight to warm the soil and germinate the seeds. Once they sprout and grow, not only do the weeds look bad, but they also compete with the desirable plants for space, light and nutrition.


To control weeds you need to first identify them. If you need help in doing this, it is a good time to check resources on weeds at the Extension office or in books at the library- or even search the Web for sites or links on weeds. If you have children in your family, this is a good time to enlist their help. They will learn to recognize weeds and will see insects that you might miss. Turn it into a game by giving them a bag or bucket to collect their weeds and see who can get the largest, strangest, and the one with the longest root system. It is especially important that they learn to pull the whole weed - and not just break the stem. Chopsticks are good weeders and so are old table forks. If they are composted, turn the compost pile frequently to prevent them from growing. Or, just simply bag them for the trash.


So what are weeds anyway? Weeds are defined as plants growing out of place. They come in all varieties - tall, short, spreading ground cover, but mostly unsightly. They are invasive and destructive to your garden plants because they take up space, light and nutrition, hindering the growth of other plants. As we move into the fall season, winter weeds will began sprouting from late September through October and possibly even through November and December depending on the weather. Winter weeds that typically cause problems in our yards are annual bluegrass, bur clover, chickweed, dandelion, henbit, lawn burweed, stinging nettle and thistle.


A thick, dense turfgrass usually identifies an area that will seldom have weed problems. So, the best advice is to follow management practices that maintain a thick turf. But a little bit goes a long way - and just enough is better. Too much high management, i.e., fertilizer, water, etc. will encourage pests, thus weakening the grass and resulting in more weeds.


If you stand above your lawn looking down at it and see either dead spots or a weak turf at this time of the year, you will probably have one or more of the weeds listed above within a month or two. Since it is always recommended to first use the least toxic weed control method, try pulling the weeds as your first technique. If that is not your cup of tea, then apply a thin layer of mulch around the desired plants and also apply it in walking paths. This will keep the soil from being compacted so less tilling is needed, less weed seed is tilled up, and it will also help keep soil temperature and moisture more uniform.


Another option to minimize winter weeds is to use a pre-emergent herbicide. Applied now before the weeds sprout, the herbicide will kill the sprouting seeds before they establish. There are several different pre-emergent herbicides that range from organic to typical herbicides.


An organic approach that has been promoted recently as a pre-emergent herbicide is corn gluten meal. Universities have proven that CGM has pre-emergent activity. Furthermore, proof has shown that it takes at least 20 pounds per 1,000 square feet - and twice or three times that rate is better. While CGM works, it typically only controls about 50 percent of the seed sprouts. Also at the 20-pound rate, the natural nitrogen in CGM is twice the recommended fertility rate needed, and this may cause problems. (More effective pre-emergent weed control is demonstrated with a 66-, 132- or 198-pound rate of CGM, but the nitrogen level gets even higher.)


Some of the inorganic chemical herbicides that may provide not only higher percent weed control, but may even be more economical include (with chemicals listed in parenthesis): Green Light Products - Amaze Grass and Weed Preventer (benefin and oryzalin), Green Light First Down Granules (benefin and trifluralin), Green Light Portrait Broadleaf Weed Preventer (isoxaben), and Green Light Betasan Crabgrass Preventer (bensulide), Other products include Vigoro Preemergent Crabgrass & Weed Control (dithopyr), Scotts Company Halts Crabgrass Preventer (pendimethalin), PBI/Gordon, Inc. Betasan (bensulide),and Fertilome Winterizer & Weed Preventer (simazine).


The key is to become better informed. First recall what weeds were a problem last year. Second, if you think you will have that problem again this winter, search for the product that has the best control of them with the least cost and environmental concerns. Third, read the label thoroughly and apply the product according to directions, following all precautions.


If you miss this pre-emergent season to control your winter weeds, you have one more chance once they have sprouted and begin growing. Prior to the weeds reaching taller than 3-4 inches, identify which ones are problems and follow with steps two and three listed above - only now searching for a post-emergent product and applying it according to directions.


All of this is a lot of extra work - when it is far easier and more economical to strive to have a thick turf from the start without having to fight the weeds. But hopefully now weed control can be a whole lot easier, and by now you see why you can't seem to garden without weeds!