Douglas asks: Many areas of my property are being overrun by the Hawaiian air plant. I have been pulling as many as possible but they seem to multiply anyway. Is there anything I can do to get rid of them?
Tropical Gardener answer: The Hawaiian air plant is known botanically as either Kalanchoe pinnatum or Bryophullum pinnatum. Both are listed on the Hawaiian Invasive Species list. Though the plant has some attractive features it should not be grown here as an ornamental. You can find seeds on the internet and occasionally local nurseries sell the plants, but unless you are ready for a takeover, do not grow this plant.
This succulent, native to Madagascar, has become a popular houseplant worldwide and has naturalized throughout tropical and subtropical regions. Its pink bell-shaped flowers are referenced in the common name “cathedral bells.” In addition to the seeds that follow the flowers and germinate quickly, the leaves produce miniature plantlets in small crotches on the leaf margins. It can also spread by underground roots. With so many ways of reproducing, the plant is also commonly known as “mother of millions.”
The Hawaiian air plant qualifies as an invasive species in several ways in addition to its rapid reproductive rate. These include fast growth, high dispersal ability and tolerance to a wide range of conditions including drought. Another reason not to grow this plant is that it can be toxic to grazing animals.
The Hawaiian air plant is a frequent volunteer in gardens as well as in open areas and is very hard to eradicate. Removal by hand works in small infestations. Bag the plants and remove them from the site or let them dry and burn them. Controlled burns can also kill the plants and slow or halt regrowth.
Probably the quickest and most effective way to kill these plants is with an herbicide containing glyphosate. Sadly this is not an environmentally friendly solution or one that is healthy for humans. Glyphosate has been shown to disrupt soil biology and is toxic to many beneficial micro- and macro-organisms including earthworms. In several studies, glyphosate has been linked to birth defects and cancer in mammals. And that’s just the tip of the iceberg. A Scientific American article on the threats this herbicide poses to human health can be found at www.scientificamerican.com/article/weed-whacking-herbicide-p/. A British publication from 2001 can be found at www.foe.co.uk/sites/default/files/downloads/impacts_glyphosate.pdf with more information. Use this product with caution. Wear personal protective equipment including gloves, protective clothing and foot coverings as well as face masks that leave very little exposed skin. Mix the product according to the directions and apply very directly to the leaves of the plants you want to kill. Try to avoid getting the product on open soil. After about six weeks you may have to return and reapply to new plants or those that lived through the first application. Good luck.
Diana Duff is a plant adviser, educator and consultant living on an organic farm in Captain Cook. 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.
Gardening Events
Wednesday-Friday: “Hawaii Coffee Association Conference and Cupping Competition” at King Kamehameha’s Kona Beach Hotel in Kailua-Kona. Opening reception Wednesday; workshops and farm tour on Thursday; presentations and cupping competition on Friday followed by HCA dinner. Info/register:www.hawaiicoffeeassoc.org/
Saturday: “Work Day at Amy Greenwell Garden,” 9 a.m. to 12:30 p.m. Meet at the Garden Visitor Center in Captain Cook. Volunteers will be able to help with garden maintenance and are invited to bring a brown bag lunch. Info: Peter at 323-3318.
Farmer Direct Markets
Wednesday: “Hooulu Farmers Market,” 9 a.m. to 2 p.m. at Sheraton Kona Resort and Spa at Keauhou Bay
Wednesday: “Sunset Farmers Market,” 2 p.m. to sunset at the north makai corner of the Kmart parking lot
Saturday: “Keauhou Farmers Market,” 8 a.m. to 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. to 2 p.m. at Amy Greenwell Garden in Captain Cook
Tuesday-Saturday: “U-Pick greens and produce,” 10 a.m. to 4 p.m. Tropical Edibles Nursery in Captain Cook
Plant Advice Lines
Anytime: konamg@ctahr.hawaii.edu
Tuesdays and Thursdays: 9 a.m. to noon at UH-CES in Kainaliu, 322-4892
Mondays, Tuesdays and Fridays: 9 a.m. to noon at UH-CES at Komohana in Hilo, 981-5199 or himga@hawaii.edu.