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Welcome to New Zealands Plant Portal. Wally Richards Weekly Garden Tips & Advice.

Gardening Articles for week ending 10th NOVEMBER 2007
Written by Wally Richards. [Photo]

There are many ways to control those unwanted plants that grow in our gardens and lawns from hand weeding to chemical weed killers. The definition of a weed is any plant growing where you do not want it to grow and is not necessarily the plants we commonly call weeds. It maybe that you have grown some flowering plant for its virtues to find over the years that the original plant self-seeded and now pops up all over the place. You either live with it or you go hell bent on eradicating every trace of it.
The best way of controlling any weed is to cut it off just below soil surface, before it seeds, and leave it on the bare soil to be absorbed back into the soil food web. You have by doing this, provided two soil enriching aspects, the roots left undisturbed, rot in the soil feeding millions of soil organisms without disrupting the beneficial fungi chains in the earth. The green top provides food for the surface feeders who quickly break down the weed and enriching your gardens.
For gardeners that know about this natural system, they cherish the appearance of weeds as each type provides elements and minerals that will make for better gardens.
The trick is of course, not to let the weeds get too big or produce seeds.
In my book “Wally’s Down to Earth Gardening Guide’ I pointed out that no weed or plant can survive if it is denied foliage for an extended period of time. All plants gain their energy from the sun through their leaves. Stop them from obtaining energy and they have to fail and die.
Take oxalis for instance, it is a bulb that throws up a set of leaves, gains energy from the sun and produces hundreds of bulblets or baby bulbs. If you take a heaped tablespoon of baking soda and add it to a litre of warm water, stir to dissolve, then add one mil of Raingard, you have made a potent dehydrator of oxalis foliage which does not harm other types of plants. If you spray this formula over the oxalis foliage on a sunny day when the ground is on the dry side the leaves of the oxalis will shrivel and die. It has not killed the bulb which will then produce another set of leaves. As soon as these appear you either apply the same solution or cut them off at ground level. If done quickly enough at the emergence of the new leaves the bulb has not gained energy but has weakened instead. Again it will try to produce leaves which should be quickly removed. At some point of time the bulb does not have any more energy left to produce foliage and it rots in the soil. Goodbye oxalis.
There is a further aspect to the oxalis problem and that is all the baby bulbs attached to the now dead parent, if you disturb the soil you will bring these babies nearer to the surface where they will also produce leaves to start the cycle over again. What you do instead is cover the soil with a layer of compost and plant any new seedlings into this layer. This action further buries your oxalis problem. Do not disturb the soil and when you flowers or vegetables are finished or harvested, just cut them off at ground level and cover the area with more compost. Simple and effective.
Chemical weed killers should be avoided at much as possible as they do a lot of damage to the health of the soil, environment and ourselves. There is also another good reason to avoid them as the price of many of them has become very expensive. Glyphosate, the most common weed killer these days sold under various trade names such as Roundup does not dissipate when it hits the soil and has a half soil life of 6 months or more dependant on the soil type. It kills soil life and worms hate it. It gets into your food crops and ends up as another chemical poison in your food chain. I believe that one day we will come to realise that Glyphosate is as bad if not worse than many of the banned chemicals such as DDT.
Lets face it, it has only been over the last 50 odd years that we have had chemical weed killers to use in our gardens and farms and before this more natural things were used, many of which can be far more effective than the chemical and less damaging to the environment or our health.
For instance gorse, black berry and other woody similar plants can be eradicated with garden lime. Change the pH making the soil more alkaline and the offending weeds fail. Ideally you cut the gorse or black berry down to near ground level and dose the surrounding area with a good amount of lime. You can also treat the stump with diesel. The lime will prevent regeneration of the gorse etc. Simple, cheap and effective. Diesel, sump oil etc, once were used to mark the lines of rugby fields in days gone by. The line would be painted with sump oil and no grass or weeds would grow in that line for a long time.
If you have a waste area where you want nothing to grow for a long time it could be a good cheaper solution.
A lady gardener rang me during the week and gave me a tip about that horrible weed, wandering jew.
She has used the following solution and told others with a wandering jew problem about it, all of whom have cleaned up the problem in a short period of time.
Go to a grocery wholesaler such as Toops and buy a 25 kilo bag of table salt, which will cost you between $10 to $15.00. Broadcast the salt over the area where the wandering jew is growing, its cheap so throw it on. You will find that the weed dies off leaving bare ground. Some new emergence will then occur and you spot treat these with a handful of salt. Later rake the area to remove the stubble and then you can lime the area and apply Magic Botanic Liquid to bring the soil back for planting up in a preferred plant. If you have other plants growing in the area they will likely die also but well established trees and shrubs should not be unduly affected. Now $15.00 worth of salt goes a long way and is cheaper than a little bottle of chemical weedkiller for $30 which does not go far.
If you have pavers and weeds grow in the cracks just sprinkle some of your salt.
Another one is sulphate of ammonia which also burns out weeds. I tried this out the other week on low weeds growing in a gravel drive. Sprinkled the sulphate of ammonia over them and now they are all brown and dead. Ideally you should lightly water the weeds about half an hour prior to applying the sulphate of ammonia so there is a little moisture to start the burning action. The advantage of sulphate of ammonia is a short residue period, unlike table salt which is much longer.
In your kitchen you already have a couple of neat, environmently friendly weed killers, vinegar and cooking oil. These can be sprayed over the foliage of weeds on a sunny day when the ground is on the dry side to burn off the weeds. Dependant on the type of weed you can dilute the two products with water to make them go further and be more economical. You need to experiment a bit to find out what dilution rate works best for each type of weed and to assist mixing with water you are best to add some Raingard.
Once again buying either a cheap cooking oil or vinegar in bulk, works out very economically on the purse and you are doing far less damage to the environment or your own personal health.
Tall weeds should be cut low with a weed eater before applying any of the more natural products suggested above. This reduces the amount of product you need to use and gives a quicker result.
One thing to remember is that these methods are non-selective and whatever you treat, preferred plants or weeds will be affected. Well established trees and shrubs should be fine.
If you want the dead weeds to disappear faster spray them with Thatch Busta.

Any Problems ring me at 0800 466464 (Palmerston North 3570606)
Email wallyjr@gardenews.co.nz
Web site www.gardenews.co.nz

Garden Pages and News at www.gardenews.co.nz
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Problems ring me at 0800 466 464 (Palmerston North 3570606)
Web site www.gardenews.co.nz

Garden Pages and News at www.gardenews.co.nz
Shar Pei pages
at www.sharpei.co.nz

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