weeds and permaculture Amanda, the interaction between impoverished soils and weeds is very interesting. Where I’m living, the original rainforest recycled nutrients from the subsoil to the leaf litter layer. This cycle was broken when the rainforest was cleared. Nutrients – especially alkaline minerals – were leached beyond the shallow root zones of the pasture grasses that replaced the rainforest. Yes, the soil became more acidic – down to an average of pH 4.5 (but I’ve seen as low as pH 3.9). Undoubtedly, the most sustainable way to reestablish the health of this former rainforest soil is to reestablish the deep-rooted trees that catch and recycle minerals from deep in the subsoil back up to the litter layer. There are native rainforest pioneers that can handle the acid soils (i.e grow out of sub-soil road-side embankments) and can initiate the regeneration process: blackwood, Commersonia, native raspberry, sandpaper fig etc. Unfortunately lantana suppresses the regeneration of the rainforest – including competing with re-colonising pioneers - by forming very dense thickets that trees can’t grow through. Therefore the tree mineral recycling system can’t reestablish, and therefore the soils can’t repair. So in the case of lantana, it’s the opposite of what you’re suggesting. This shrubby weed is actually maintaining a degraded soil state by not allowing a soil regenerating forest system to reestablish. Some people have argued that the topsoil under lantana is good, and useful for cropping once you clear it. Superficially the soil texture under lantana appears ok with a humus layer from leaf drop. But soil tests indicate a high acidity and low levels of alkaline minerals, especially deficient in potassium. This dovetails into this absence of deep roots to bring-up nutrients from the subsoil - lantana is comparatively shallow rooted. It appears to be a similar situation with invasive blackberry in temperate Australia where it can invade undisturbed forest - forming an understorey that prevents the regeneration of the sclerophyll trees (which require sunlight for regeneration). By preventing the regeneration of the forest the blackberry is also disrupting the trees deep-rooted mineral recycling system. Some people believe that somehow weeds are correcting the damage caused by people. But the reality is that we have pioneer native plants that are in context with the local ecology. Rampant introduced weeds appear to be contributing to degradation by destroying the structure of the native ecosystems. Introducing a rampant weed to a native ecosystem is the ecological equivalent of introducing a killer flu to an indigenous people with no previous exposure. Native ecologies have no resistance to many rampant weeds. Also many weeds are often toxic to native wildlife with no evolutionary exposure. Lantana, croften weed, moth vine are just some of the more toxic plants that native wildlife here generally don’t eat. This in turn puts more pressure on the surviving native plants. The native rainforest grasses that manage to find a weed free space are over-grazed by native herbivores like pademelon wallabies, which are hard-pressed to find their original food due to the weed wipeout. So weeds have a cascading impact on the native ecology. While I know permaculture isn’t responsible for these particular weeds, the network still needs to be cognitive of weed risks, and show maturity if we are to successfully provide a total systems approach. We have many lessons on what not to do with plant introduction - so why risk repeating the mistakes of the past? As McMinn pointed out, there are many introduced domesticated food plants that are not a significant weed risk, and their use should be encouraged. However, with rampant self-regenerating plants, it's better to use natives which have native herbivores that can keep them in check. It should be basic permaculture principle. Cheers.