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It’s good to share, but beware. Plants and personal responsibility by Vicki Boxell

by Vicki Boxell — last modified Jul 23, 2014 02:23 PM
The double edged sword of super productive permie plants.

 

Plants are amazing things. They can fix most of the world’s problems if used correctly and are the source of a huge amount of what we need in our daily lives.

As permaculture folk we want to fix degraded land and create complex ecosystems and we do this with plants as they can do it quickly. Unfortunately their speed of growth can sometimes also be a negative thing. Thousands of dollars and volunteer hours go towards removing escaped vegetation; lots of poison, too.

Plant selection and use is a complex and controversial subject and is a reason why permaculture has sometimes been denigrated. Having studied and worked in both environmental restoration and permaculture I have some conflicted ideas about plants out of place aka exotics aka weeds. Some plants are brilliant, having multiple uses but some are just so good at propagating themselves they become rampant and have been banned from growing in certain areas, despite how useful they might be.

Tagasaste

Personal responsibility is a strong ethos of permaculture, so I am going to outline my concerns with the trend of sharing seeds without clearly considering the consequences.

Novel ecosystems

The term novel ecosystems (Hobbs, 2006) encompasses the many habitats on earth that have been altered in some way. Most habitats have been changed by the inclusion or removal of species, on purpose or accidentally; we can never go back to having pristine landscapes of purely indigenous species. Naturalised plants, that is introduced species which need no help to survive in a new place, have varying degrees of influence on bushland ecosystems, areas that are important repositories for endemic species including invertebrate populations. Earth care would have us protect remaining pre-settlement areas for health and wellbeing reasons.

Through clever design we can integrate a lot more food plants and other useful species into our environment but we need to be careful not to accidentally reduce biodiversity by letting many species be overgrown by one rampant one.

Using naturalised plants

There are many reasons to use existing ‘weedy’ or naturalised species in an area - biomass production, shelter and insect habitats, for instance. When trying to improve degraded sites the idea may be entertained that any plant that will grow in a place should be encouraged. If a site is degraded it needs any plant to grow there to protect and improve the soil. However some newly introduced plants can settle into an area too quickly, becoming costly to remove if they turn out to be a bit more voracious than one had hoped or expected.

Ideally, before planting, the permie designer would look around and see what is already nearby to fulfil their needs for vegetation before introducing new species to an area. If a plant is a declared or environmental weed in another place it is worth researching to make sure the same thing won’t happen on your site.  There are always plenty of choices for all but the most marginal of conditions.

While I agree with Holmgren in his “Weeds or Wild Nature” essay that there has been demonisation of certain species, we should be careful not to dismiss the fact that some plants do escape into otherwise healthy bushland, changing the ecosystem structure.  Many naturalised species are not encroaching any further than they have done since they settled in however I would suggest that there are some species recommended in permaculture readings that reproduce a bit too successfully where we are and as with all things, the better educated we are before we start, the less costly mistakes will be made.

Why are some plants more problematic than others

This depends on the plant’s life cycle, method of propagation and their self-defence mechanisms.

Self-seeding is good, sometimes.

Part of a good permaculture garden involves finding some edibles that will self-seed. For some plants this is fine, we water and look after the soil so it is good enough to support self sowing vegetables. Lettuces, rocket, parsley, and a range of other vegetables are a fantastic set of foodstuffs to happen on their own. Even parsley can take over a lot of ground space, which is okay if you love parsley and can share it around, but if you don't like weeding, all you will end up with is parsley (make friends with a kebab shop and give it to them for their tabboleh).

Other plants self sowing isn’t so beneficial for suburban gardens, though. This is due to their size, rate of reproduction or some other reproductive behaviour.  An example would be some extremely useful trees, Albizia lophantha and Acacia saligna. Both species kept coming up each year for a number of years in our garden and we would let them grow where they wanted. But only ever one at a time would come up and they are short lived and easy to prune. We knew we could manage them. Of course, in South Africa the Acacia saligna has become a big problem, changing ecosystem structure and fire regimes in the fynbos.  It grows better there than it does here.

Some of the more common fodder trees will self-seed very easily, too, such as Leucaena leucocephala and Tagasaste. In some areas the seeds will not be viable but where they can take hold and aren't being pruned regularly for fodder or mulching, especially while in flower, there could soon be thousands of shrubby trees popping up. Management of this biomass is vitally important, making a huge difference to the amount of shade or sun you have and how much mulch and sticks for firewood you can end up with.

 

Part two of this article (in the next enews) will give some examples of why some plants can be a bit too easy to propagate.