John asks: I have been using products containing glyphosate (like Roundup) to control weeds on my property but want to find a more organically friendly alternative. Can you recommend anything?
John asks: I have been using products containing glyphosate (like Roundup) to control weeds on my property but want to find a more organically friendly alternative. Can you recommend anything?
Tropical Gardener answer: It is a good idea to consider alternatives to chemical herbicides to maintain soil health. Glyphosate and other chemical pesticides can reduce the microbial activity in the soil, which can negatively affect soil and plant health.
Of course, the meditative practice of weed pulling is always an option. Using a hoe or hula hoe (also known as a stirrup hoe) to remove weeds when they are small is another possibility. These techniques remove the plant and its roots so you need only repeat this when new weeds arrive.
Maintaining healthy soil means keeping it covered. Mulch can cover the soil and lesson weed issues. Many ground covers will suppress weeds and some take nitrogen from the air and fix it into the soil. Weeds also cover the soil. Many farmers and gardeners just mow or weed whack weeds (before they go to seed) letting their biomass remain in place as mulch.
Some organic gardeners use gas-powered torches to burn down the tops of weeds. If the weeds are not near plants that could be affected by the burning, this can work. Burning does not kill the roots, however, so you may have to repeat this practice fairly often.
Environmentally concerned growers also use products that contain acetic acid, fatty acids and essential oils as herbicides. Spraying acetic acid, or vinegar, will burn down the weeds, much like the torch but leave the roots in place and eventually the weed may grow back. The same is actually true of products containing fatty acids and essential oil. In most cases, these products will not harm soil microbes and are not toxic to aquatic life.
Pelargonic acid is a fatty acid that is often found in organic weed killers. Herbicides containing essential oils like peppermint, pine, clove or citronella are becoming more popular and available. Though the active ingredients in these formulations are safe, it is a good idea to check the “inert ingredients” to be sure toxic surfactants are not included.
Weed prevention can be achieved to some degree by applying powdered corn gluten to areas where weeds normally grow. It is a safe product but is only effective against new weed growth not established weeds.
Some questions that appear here were originally directed to Kona’s Certified Master Gardeners. You may contact them with questions at konamg@ctahr.hawaii.edu.
Diana Duff is a plant adviser, educator and consultant living on an organic farm in Captain Cook.
Gardening events
Monday: Hawaii Tropical Fruit Growers meeting; 7-9 p.m. at 81-6393 Mamalahoa Highway in Kealakekua, about 1/2 mile south of Konawaena Elementary School Road. Several producers have been invited to discuss growing and processing dragon fruit. Info:Brian Lievens, 895-8753 or greenwizard@hawaii.rr.com.
Friday: Coffee Pruning Workshop; 9 a.m. at Bob Nelson’s Farm in Kainaliu (makai of the Kona Joe sign) with Bob Smith and Bob Nelson. Learn the value of pruning correctly. Free to Kona Coffee Farmers Association members; others $10 toward KCFA membership of $25. Info: Suzanne Shriner, suzanne@coffeeofkona.com
Saturday: Gardening in Hawaii; 10-11:30 a.m. at Kailua-Kona Public Library with Diana Duff. Free program for the Community Seed Library, sponsored by Friends of the Libraries, Kona. Learn to garden successfully in Hawaii. Info: Natalie, nehamah47@gmail.com.
Farmer direct markets
Wednesday: Hooulu Farmers Market; 9 a.m.-2 p.m. at the Sheraton Kona Resort and Spa at Keauhou Bay
Wednesday: Sunset Farmers Market; 2 p.m.-sunset at the north makai corner of the Kmart parking lot
Saturday: Keauhou Farmers Market; 8 a.m.-noon at Keauhou Shopping Center
Kamuela Farmer’s Market; 7 a.m. to noon at Pukalani Stables
Sunday: South Kona Green Market; 9 a.m.-2 p.m. at Amy B.H. Greenwell Garden in Captain Cook
Monday-Saturday: U-Pick greens and produce; 10 a.m.-4 p.m. at Tropical Edibles Nursery in Captain Cook
Plant advice lines
Anytime: konamg@ctahr.hawaii.edu
Thursday: 9 a.m.-noon at UH-CES in Kainaliu, 322-4892
Monday, Tuesday and Friday: 9 a.m.-noon at UH-CES in Hilo, 981-5199, himga@hawaii.edu