Weeds

Posted by on Nov 12, 2008 in Gardening | No Comments

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Weeds are opportunistic plants that develop in disturbed environments. Their action can bring balance to the topsoil mining nutrients from below and making it available. However some species in some conditions are so invasive they can slow the natural succession phasing of growth. In these situations, a small, considerate and deliberate intervention can restore health to the ecology.

The most effective means to control invasive species has to be taken on a case by case basis. The use of herbicide was quoted by a local bush regenerator as amplifying the effect of human interaction one hundred fold.

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A person working with the health of the system in mind can effect a huge change, this is sometimes necessary when an over dominant species has halted the natural phasing of the forest. However; Indiscriminate spraying of herbicides has a massive environmental cost it can destroy fertility in the soils and undermines the natural processes. Persistent herbicides remain and are concentrated up the food chain. Run off can pollute water ways. Particular products and additives, such as the surfactant used to stick round-up to plants has known toxic effects on frogs.

Plant identification and understanding are the greatest of assets. Knowledge of the land and its history can give a clear perspective on whether the regrowth is beneficial for soil re-balancing or if needs intervention.

IMG_0786 This was the focus of our ABT. Plant identification is an art that notes the features. Many plants do not differentiate enough when young (and most easily controlled). Leaf shape and colour, flower, fruit, structure, smell, root system and location are all used to make a positive identification.

IMG_0790 If you are unable to identify a species, a pressing is made, details are noted and can then be sent to a herbarium for them to catalog. IMG_0792

A very effective and efficient way of identifying plants is to find someone that already knows a great deal. Plant varieties and species can be very localized, so the more experience your assistant has in the same area, the more likely you are to get a positive identification.

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Some Jargon Native : These are plants that are indigenous to the country Endemic : This is more specific, plants that are indigenous to a particular area. Naturalised : These are species from elsewhere that have adapted to a new area and made it home. Successional Phasing : A forest develops in phases, first come the grasses, then fast growing woodier, taller species. Then pioneer trees.

One of the critiques of Permaculture is that it encourages the introduction of new species to an ecology. The ramifications of bringing in new species are often far-reaching and little known. Many out of control species are garden escapees.

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This is Yarrow, used as a superb compost activator.

Some topsoil was bought and trucked in to the trust without seeing the source with it came a whole soil seedbank that contained some of the most noxious weeds to the area.

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Nutgrass and Castor oil plant are two that once established will run and are next to impossible to fully eradicate. We heard stories of nutgrass seed being introduced in the tracks of hired machinery.

IMG_0775 This is a native tobacco bush, often regarded as a weedy species it actually acts as a nursery plant for the next phase of successional growth.

IMG_0774 There are many different grass species in the area. The local rule tends to be if the cows, roo’s or horses won’t eat it, it is a weed.

One of the techniques for plant control taught to us was the cut, scrape and paint.

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The Cut!

The outer layer of bark is quickly scraped away revealing the green layer where the plant transports the nutrients around

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It is then painted with the herbicide. Once the plant is cut, the vascular system shuts down very quickly. It is in this time that poison must be painted on to be effective.

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This particular species is on a government list that controls the most noxious weeds. Land owners are obligated by law to control it on their property.

The permaforest trust is on a 100 acre title, only the top 10 acres are certified organic where plants are controlled by hand. The remaining 90 acres are controlled with the use of Round-up (Glycosulphate) a relatively benign, short lived and extremely widespread herbicide produced by Monsanto.