Dealing With Weeds in Walkways
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Moss-Aside™ Moss Killer
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Weed-Aside™ Herbicidal Soap
Q. I've been searching for a responsible way to keep my very large brick terrace free of weeds. (I will not use Roundup.) All the advice I can find is about weeds in garden beds or lawns, not growing up between bricks. I tried pulling the weeds out by hand after a good rain but they keep returning.
---"Newbie" in Alexandria, VA
A. Well, Nature abhors a vacuum Newbie; and Nature really seems to love filling in those little spaces between bricks and pavers with her favorite plants, which are apparently not yours. Forget hand pulling; it's a never-ending battle—long term it's just going to wear out your back and knees. (But when and if you do hand pull, be sure and compost the weeds; there are lots of good nutrients in those unwanted plants!)
Instead of pulling, think about using the loosening power of water without your needing to get physical. VERY sharp streams of water—like from a pressure washer—will blast out the existing plants and blow out the soil and bits of schmutz in the cracks that allow new weeds to germinate. And it'll keep the bricks nice and clean….
Newbie's email continues: "I've had some success with a home-made weed killer using horticultural vinegar but the weeds always come back."
Vinegars labeled as 'horticultural' have a much higher level of acidity than grocery store vinegar. (Typically, 8 to 20% acidity versus the store bought 5%.) Used on a hot and dry day, they are very effective at killing any plants they soak. But they work best at full strength; not in home-made mixtures. And be careful! You must wear eye protection and keep children and pets away from the area while you're spraying. Vinegar isn't toxic, but you don't want to get any in your eyes.
…Which leads me to suggest one of the newer iron-based herbicides as a much safer choice. (And from what I hear from our listeners, iron-based herbicides are easier to find both online and at retail.) Look for the letters HEDTA or FeHEDTA as the active ingredient on product labels. Herbicidal soap sprays are another option; just be sure to spray when it's hot and dry, and then rinse the area down the next day so it isn't slippery.
We now conclude with Newbie's final email's comment: "Would it prevent new weed growth If I apply horticultural vinegar to kill the surface weeds followed by an application of corn gluten meal?"
My answer is the one I was always told not to use back when I was a manager of a large staff of people: "Yes, but…".
(Yes, I actually was a manager; a darned poor one. The business I was running did very well but the morale was so low that members of my staff could have crawled underneath a snake with a high hat on.)
Now: High-strength vinegar will kill existing weeds—especially in hot and dry conditions. Again, be sure to wear eye protection—or use one of the new iron-based herbicides for the initial knockdown instead. Then a dusting of the correct amount of corn gluten meal should prevent any new weed seeds from germinating for about six weeks at a pop. So if you want a head-on fight, this is a well-planned one. But I'd rather take a cue from The Champ's famous "Rumble in the Jungle" and play Rope a Dope…
And no, that doesn't mean that I want Newbie to lay back and do nothing for seven rounds. Just the opposite. I want Newbie to plant those areas deliberately instead. Again, the essential problem here is that weeds love to grow in those tiny little cervices between bricks and pavers—making almost any 'solution' an endlessly repetitive task. (As Ozymandias once noted, "all solutions are temporary". Or was that the slogan for Duct Tape?)
At any rate, instead of fighting Nature head-on, consider deliberately growing attractive and useful plants in those gaps. There are at least two lines of branded plants sold precisely for this purpose: "Stepables" and "Jeepers Creepers". (I don't name them, folks; I just report them.) Some of these plants are sold as potential lawn replacements, but a good number are tough and low-growing gap-filling wonders; including some that are fragrant when you step on them.
The plants involved aren't exclusive to those companies, but the brands have done a lot to promote the idea of using plants in these kinds of problem places; and you can do a lot of preliminary research on your potential choices just by searching each company's offerings online. Then buy them wherever you want. But wherever you eventually purchase the material, the best answer to this problem is to plant low growing perennial groundcovers.
I really like low growing herbs for this purpose, especially creeping thyme and lemon thyme (and many other thymes) as they release a pleasant scent when you walk on them. (I had this happen for me accidentally one year when some lemon thyme growing in a big half whiskey barrel 'self-seeded' an open area between pavers in our patio.)
Low growing sedges and sedums—the latter the anchor plant of green roof systems—are also great for this use, as are many other plants. So do your research, plant in the spring and weed no more!