Axing oxalis and other weeds
Weeds are simply plants that are growing where you do not want them.
Early settlers introduced a great many of the plants we now have to work hard to eradicate, among them, the garden pest oxalis, which was I believe, brought here for its flowers.
Before herbicides, weeding was done by hand. The pulled weeds were either composted or left in a bucket of water to break down. In waste areas, paths and drives, weeds were treated with boiling water, salt or oil.
Herbicides introduced convenience. A lawn could be sprayed to kill broadleaf weeds without killing the grasses. Then along came glyphosate patented by Monsanto in the early 1970s as the active ingredient in the ‘magic bullet’ herbicide Roundup, originally considered safe to the environment and our health.
However, the length of time glyphosate stays active in the soil can be a lot longer than previously thought. Its half-life in soil ranges between a few days to several months, or even a year, depending on soil composition.
It has been labelled ‘‘a probable carcinogen’’ by the World Health Organisation.
A weed science lecturer at Massey
A problem with herbicides is the damage they do to soil life – the beneficial microbes and fungi.
University, Dr Kerry Harrington says in Chemistry World: ‘I don’t think there should be knee-jerk banning of the herbicide, but . . . perhaps we need to go back to using glyphosate for the jobs it was originally designed for – preparing seed-beds for planting crops and controlling weeds around the streets, and stop applying it over the top of foodstuffs, especially fairly close to harvest time.’’
I agree that glyphosate should never be sprayed over food crops such as carrots, wheat, potatoes and cereals prior to harvest.
For a table of 70 common and troublesome weeds, with information about each and their (mostly commercial) controls, see massey.ac.nz/massey/learning/colleges/college-ofsciences/clinics-and-services/weedsdatabase/weeds-database_home.cfm
A problem with herbicides is the damage they do to soil life – the beneficial microbes and fungi. Offset this by adding Mycorrcin to the weed killer. Mycorrcin helps to restore soil life back to normal.
Which brings us back to oxalis. Referencing my article gardenews.co.nz/ oxalis.htm a reader queried my advice about not disturbing the soil during efforts to eradicate the weed.
The problem with digging out oxalis is that the bulbs have tiny bulblets which fall off the parent when disturbed. These then become large enough to throw up a set of leaves and by that time they have bulblets of their own.
Every disturbance increases the number of future bulbs.
Chickens are great foragers capable of seeing and eating all the bulblets, but that is not a solution for most people.
Try using a layer of cardboard. Cut the foliage to ground level and place a good layer of clean purchased compost over the cardboard to plant into.
Later on when oxalis foliage starts to appear, cut the leaves off. This weakens the bulb by denying it energy from the sun. Keep cutting off the foliage as soon as it appears and the bulb runs out of puff and rots in the soil.
Problems ring me at 0800 466464 (Palmerston North 357 0606), email email@example.com website www.gardenews.co.nz
Oxalis is one of the most troublesome weeds in the garden and requires a strategic approach if gardeners are to get on top of it.