Ax­ing ox­alis and other weeds

The Tribune (NZ) - - GARDENING - WALLY RICHARDS

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 wal­lyjr@gar­de­news.co.nz web­site www.gar­de­news.co.nz

PHOTO: FAIRFAX 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.

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