Khaki Weed (Alternanthera Pungens)
Photo Kim and Forest Starr
Because of its sharp, stinging burrs and exceptional invasive nature, khaki weed poses a serious threat to the environment and culture in Hawaii.
The plant is exceptionally invasive because of (at least) two anatomic features.
1) Its ability to grow laterally along the ground, even beneath the height of mowed lawn level. Consequently casual mowing does not interrupt the seed setting process, as mowing does with many other common weeds.
2) A mature plant may produce hundreds of burr-covered seeds. Rate of fertility of seeds appears to be very high. Seed-burrs attach to footwear, tires, clothing, etc....and are transported far distances that way. It is likely that the many marathons, hosted on Oahu, contribute significantly to the spread of the weed. Seeds are also spread by lawn-maintenance equipment, wind, and birds that eat the seeds.
Khaki Weed Tap Root--photo Andrew Lawrence
Khaki weed is usually supported by a single woody tap root. Though sometimes the prostate stems that extend from the central tap root, also launch tap roots themselves. The plant may remain dormant for periods, though the tap root is perennial and very hardy. Khaki weed is said to flower June through October...at least in temperate climates.* In Hawaii's more tropical climate, it 'blooms' year round.
Khaki weed is registered as a 'Declared Plant' of high priority by the State Government of South Australia (SA) and is considered a very serious weed threat in that State.. According to David Deer, of the Animal and Plant Control Commission, in SA, Khaki weed is a "very difficult weed to control as it establishes on dry areas that have little competition, extensive root structure, and resilience to chemicals makes control difficult."
For more information, see the (Pdf) "Declared Plant Policy" for Khaki weed, published by the Government of South Australia. You may also see Effect on Animals and Medicinal & chemical properties.
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* This AU reference says Dec. through May, but that's the Southern hemisphere.
4 comments:
Khaki weed: Lot and lots of information on the plant but very little info on how to get rid of it except by pulling it up, which, is pretty much common sense. So much telling us about it, but nothing on control.
I lived near Kekaha Kauai Hawaii in the late 1960s to early 1970s. This weed was wide-spread in the beach forested areas from Waimea to Barking Sands. It loved to grow wild in the sand with little to zero soil. We used to test our toughness (stupidity) by running barefoot through wide growths of the weed. It was especially "fun" to get their burrs stuck between our toes.
Great info..
I have had good results from the following. Pull up any khaki weeds that have stickers, If they haven’t developed stickers yet I spray with Glyphosate (round up type spray) then pull them up after they die. Also very important to use pre-emergent. I used Andersons Balan and/or Hi Yield turf and ornamental weed and grass stopper. I had at least a 90% decrease in the amount of khaki weed in what was two fully covered patches of at least 400 square feet. Have to stay on top of it and kill it before the seeds (or stickers) come out. I had unknowingly spread it the first year I lived on this property not knowing anything about khaki weed. So I am still dealing with a few patches but nothing like it was the first season. The first time I realized what they were was when my 5 dogs had 4 paws full of stickers that I had to remove. Very motivational for me. I went out and scraped the top of those areas with a hoe about 3 to 4 inches deep and got rid of all of the dirt and stickers (all the stickers that I could see). Very tedious but worth it. The area where I live is North Central Texas. I hope this is helpful.
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