Tallahassee Democrat
Photos by Steve Chandler
July 25, 2014
By Steve Chandler
Photos by Steve Chandler
Most people become concerned about weed control sometime about the middle of summer when their lawn is struggling with the heat and the weeds seem to be thriving. Their question then is usually “How do I save my lawn but kill all the weeds?” They may want to know “Why do the weeds keep coming back in my garden and flowerbeds after I just pulled them out?” They are frustrated that “weeds somehow showed up in the flower pots I just got from the nursery” or maybe “I added topsoil to the bare spots in my lawn and watered to encourage the grass, but weeds came up instead!”
To be successful with weed control, you need to have a long-term plan. The first step in the plan is to determine what a weed is: anything that you did not plant that is competing for water, sunlight and nutrients with what you did plant. Within that broad definition can be plants that you don’t like but your neighbor thinks are pretty, plants that started from seeds that blew in on the wind or were carried in by the birds or other animals, and even plants that make you sneeze or have stickers that poke barefooted kids. Regardless of what you define as a weed, to control it, you will need to get to know the plant well enough to understand how to minimize its impact on your desirable plants.
Identifying the weed is important for understanding its lifecycle, its reproductive strategy and its ideal conditions for success – so you will have a better chance of killing it. Is it a spring weed that germinates in winter, blooms in spring and spreads windborne seeds by summer {dandelion, (Taraxacum officinale)}? Is it a summer weed that doesn’t show up until the soil is warm enough for the seeds it dropped last fall to germinate this summer {chamberbitter, (Phylanthus urinaria)}?
You will also have to decide what weed control strategies best fit your circumstances. Are your weeds mostly in the lawn where you’re comfortable using a herbicide on the weeds that won’t hurt the grass? If so, you will probably be applying the herbicide to stop the weed from germinating (pre-emergence) and again when some of the weeds come up to prevent them from making seeds for next season (post-emergence)? If you’re putting in a new flower or garden bed, you can bet that there will already be weed seeds in the soil that you till and level for the new bed. Gardeners often “solarize” newly tilled soil with a sheet of black plastic held down over it so the sun can heat the plastic and kill the weed seeds in the soil below it. Once the soil is solarized, adding a layer of mulch is commonly done to discourage weed growth and hold in moisture, but if the mulch contains weed seeds, you will be putting weeds in the bed, too. Mulch that’s made from collected yard waste may be free, but it’s usually made from the stuff people pull out of their yards and put by the curb (often weeds!). Weeds that pop up after adding topsoil to the lawn or appear out of nowhere in a plant you recently re-potted probably came as seeds in the topsoil or potting soil you purchased. The soil wasn’t sterile when you bought it.
“Weeding” – the act of pulling out weeds – takes a lot of a gardener’s time and it is far from foolproof. The most common shortcoming is failing to pull up the entire weed, leaving the roots behind to sprout anew. Lots of weeds have a long taproot{like Florida pusley, (Richardia scabra L.)} or run along the ground rooting as they go {like (Oxalis florida)} so pulling off the top of the plant without getting the root will just slow them down. Chamberbitter will even drop its seeds onto the ground while you shake the soil off its roots when you pull up the plant. Pull up the whole plant and don’t forget to bag the weeds you pull to remove them and their seeds from your garden or flowerbed.
Mowing can help control weeds. Mow tall weeds before they mature enough to go to seed, otherwise the mowing may help spread the seeds around. That may happen with spring emergent weeds that arise while the grass is still dormant and it seems too early in the season to mow. The mower may miss weeds that grow horizontally to the ground altogether and you may have to try herbicide to control them. Be sure to clean the mower after use to remove any weed seeds that may be on it.
It may take a few seasons to see results, but with a good long-term plan in practice, you should be able to control your weeds with less and less effort.
Steve Chandler is a Master Gardener and volunteer writer for Leon County UF/IFAS Extension. For gardening questions, email us at Ask-A-Mastergardener@leoncountyfl.gov
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