Permaculturing in Portugal

One family's attempts to live in a more planet-friendly way

Invasive weeds or Earth healers?

After posting about nettles and docks, I got to thinking about brambles (Rubus fruticosus) and bracken (Pteridium aquilinum) as well. Also mint (Mentha arvensis) which we have in abundance and which spreads in a similar fashion, and mimosa (Acacia dealbata) which we don’t have on the quinta but which is another “problem” plant in Portugal. All these plants are vigorous, resilient and quickly outcompete most other herbaceous species. The primary means of their rapid spread and apparent monocultural tendency are their extensive creeping rhizomatous root systems.

Urtica dioica, Rubus fruticosa, Pteridium aquilinum, Acacia dealbata

Nettles, brambles, bracken and mimosa

What I was thinking about was what do all these plants have in common besides these characteristics? What’s their role in nature? Is there an analogous process we can easily relate to that’s more useful and true to the state of things than this notion of “noxious weeds”?

The first thing that’s apparent is that invasive species are responses to disturbance: to the soil itself, or to its chemical/mineral balance (nettles grow in response to nitrate pollution as much as to ground disturbance; bracken, brambles and mimosa grow on impoverished and exposed soils). These species very quickly form a dense network of fibrous roots over a disturbed area like nothing so much as the strands of fibrin in a blood clot forming across an open wound. Their vegetative growth above the surface becomes equally thick and impenetrable, deterring further disturbance by sheer physical presence, thorns, stinging hairs, or toxicological agents (like bracken’s cyanogenic glucosides which precipitate rapid respiratory failure in grazing animals).

While doing their utmost to prevent further disturbance, these species work hard below the surface to heal and condition the soil. Rhizome growth rapidly breaks up compacted ground (bracken, brambles, mimosa) or forms a particle-accumulating mat in waterlogged areas (mint). Depleted soils have their fertility restored by nitrogen fixation (mimosa, gorse, broom and other members of the Fabaceae/Leguminosae), mineral accumulation and copious amounts of rich humus (nettles, bracken, mint). Their leaf litter also helps restore soil structure and provide a protective mulch preventing excessive moisture and mineral loss, and allowing the recolonisation of the soil by all the various invertebrate species that help break down the litter, creating and maintaining a healthy soil ecology.

Urtica dioica, Rubus fruticosa, Mentha arvensis

Mint, brambles and nettles coexisting on our middle terrace

As time passes and soil vitality and health is restored, species diversity increases. Deep-rooted herbaceous species which can penetrate the thick rhizomatous layer take hold, trees grow, and these ‘clotting’ species become less dominant, to be succeeded eventually by the natural climax vegetation of the area.

There’s a widespread tendency to see these plants as “invasive”, “destructive”, even “evil”, “monstrous”, something to be waged war on, battled, exterminated. That’s a nonsense — rampant (Jungian) projection on the part of humankind. It’s not the plants that have these qualities so much as the human assault on nature which creates the conditions requiring their intervention. And as for “taking over”, as David Theodoropoulos writes, “the fossil record is clear – invasion increases biodiversity (Cornell & Lawton 1992), and the experimental record indicates that the greater the rate of invasion, the higher the diversity of the resulting assemblages (Robinson & Edgemon 1988). As Turner (1996) stated, “life evolves at the edge of chaos, the area of maximum vitality and change.””

How to work with them rather than against them when their very nature is all about keeping the likes of us well away? Well there’s the challenge. Don’t wound the soil in the first place would be the obvious conclusion.

Back to Masanobu Fukuoka: “If we throw mother nature out the window, she comes back in the door with a pitchfork.” His no-till methods are something I’m becoming more and more convinced about and intending to follow.

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  1. John Peter Thompson May 29, 2009

    Your description of invasive plant species is how I present them in my talks: the band-aids of nature. Of course there are natives that do the same, but they can be crowded out by the more efficient non natives. Great essay…wonderfully written. I hope to write a follow up @Invasive Notes shortly.

  2. Quinta do Vale May 29, 2009

    Thanks John. I’ll keep an eye out for that.

    Of course, it’s never quite so simple is it? The fact is that the human race is a part of nature too, irrespective of how we perceive ourselves, and we have our role to play whether we’re conscious of it or not. One thing that caught my attention in David Theodoropoulos‘s piece that I quoted is this:

    “Ecosystems often are attracted to disequilibrium and are intrinsically unpredictable. Modern ecological theory indicates that many ecosystems self-organize towards critical states that are susceptible to catastrophic events which in turn are essential to the maintenance of biodiversity.”

    and he recommends Jack Turner’s The Abstract Wild for more on this.

    Taking this statement together with my preceding one, it becomes entirely conceivable that man’s ignorant messing with nature is as much part of nature’s self-organisation towards critical states as anything we observe happening independently of man’s intervention, so a minimal interventionist attitude on our part may be equally inappropriate. As ever, it seems to be a matter of getting the balance right. Clearly it isn’t at present or we would have vibrant healthy ecosystems rather than increasing destruction, pollution and desertification. But who’s to say that our progressive and rapidly increasing collective consciousness of this isn’t equally nature’s way of bringing this all back from the brink?

  3. mike May 30, 2009

    stunning! and even at the early stage of soil recovery, these plants are useful of course: mint and nettles quite edible… bracken makes a soft bed, brambles of course are good for the goats and produce excellent fruit, and mimosa… well it’s beautiful and here is some info about the plants possibilties:

    now dock….arggggggh!

  4. Quinta do Vale May 30, 2009

    Ahhhh … same common name but different plant. I was writing about Acacia dealbata not Mimosa pudica. :-) It’s another Australian import.

    But yes — it has its uses. Great for the bees.

    Right … off for a glass of nettle and carrot juice …

  5. Mark Krueger May 30, 2009

    What wonderful insight, Wendy. What would we do without our dear scabs, even if we do pick at them.?Friends of fibrin unite! Years ago, I realized that my farmer uncle’s corn/soybean fields in midwest USA were essentially dead by this nitrate poisoning ploughitis. The soil was like concrete. I’d tag along in the hand hoeing weeding process. It was dreadful work, but especially in its absurdity. I could tell things were not well. You’ve humbled my personal knee jerk response to dear weeds.

    I was inspired by Rodale in the mid 1960’s. He’d speak of tilth and divine composition; it made whole sense. I’d tell my ag relatives, and they thought me a pariah, and still do. Ruth Stout and her heaps o mulch made so much sense, too. Soil loves company, and that ain’t misery. Ag is agonizing, sterile in it’s dysconception, death unto dearth. Thanks for your, and their, dirty vast mindfulness.

    Rodale spoke of the natural deep mining of nutrients of those bedeviling, going to hell, deep rooting weeds. It made sense, and still does. As others mentioned, likely the weeds are more nutritious than the hybrittle species of pyramided carbo monoiacal enslaved plant buddies. Bring the soys back home! Mend the dyscorntinuity!

    Question though……. What of these extreme alien species that parachute in from half of a planet away and take over like a plague? Google: morgellons. This appears to be beyond fibrin, more like a dread creepy crawly. I reckon that that’s all well and eventually good, but it sure seems like madness, just like what I recently described as global swarming by humanity. It sure looks and feels like a dieaspora fungus amongus nasty invasion of the ipod people nightmare.

    In North America, there are now drastic shifts of critters that are two to four hundred miles farther north than their near historic territory, and the shift happened in a decade or two. It seems to be hard on the invaders and those invaded.

    I once spoke to a Native American in the know who was Nez Perce and married a Navajo. He told me of how the Navajo, a tribe highly revered in its usefulness to white America, some centuries ago invaded the locals, like Anasazi and Hopi, and destroyed or intensely warped their cultures. So, it happens all the time everywhere and seems to be in the scheming of it all. But I do wonder, in dumb sentience, if aliens, like ourselves, or invasive botanical species like kuzu et al, are aberrantics too toxic to bear.

    I do hope we wake up soon and begin soiling ourselves, in a really wellthful way. Go permaculture!

    Thanks Wendy and all of you who care for earth and veg,
    Mark Krueger

  6. Quinta do Vale May 30, 2009

    Hey Mark!

    Question though……. What of these extreme alien species that parachute in from half of a planet away and take over like a plague? Google: morgellons. This appears to be beyond fibrin, more like a dread creepy crawly. I reckon that that’s all well and eventually good, but it sure seems like madness, just like what I recently described as global swarming by humanity. It sure looks and feels like a dieaspora fungus amongus nasty invasion of the ipod people nightmare.

    I think you just answered your own question. The bigger the wound, the bigger the scab needed to cover it. The state of the ‘States soiled self calls for it. We’re in ER territory: drama! speed! intensity! OTT acting! It’s about treating like with like. Native species aren’t up to it because they’ve been well and truly subjugated. It has to be something “alien” that’s going to get in there fast and furious (you get my Tokyo drift?) and freak us out in the process. If humans are insanely out-of-control destructive in what they’re doing to the natural world, then we invite the response of something insanely out-of-control constructive to repair the damage, and of course we’re the agents of our own undoing every time. Kudzu/kuzu is a nitrogen fixer and mineral accumulator, halts soil erosion, produces high quality nutritious forage (hence humus), and may even be a good treatment for alcoholism.

    I last visited the ‘States for Thanksgiving 2007. Flew to Colorado over the midwest. I could hardly hold back the tears all that vast interminable distance between the east coast and the Rockies. At that time of year, the veneer of plant life left clinging to the surface was so pitifully thin and sickly it felt like I was looking at land just one teetering stagger away from annihilation. It was heartbreaking. That experience was one big log on the fire of what finally got me to the point of burnout with this way we live and determined to try and do something to change it.

    And I think this notion about “alien” and “native” species is a bit of a red herring. Species have always migrated about the planet one way or another. No ecosystem is static. Everything came from Pangaea originally.

  7. Mark Krueger June 1, 2009

    Thanks Wendy.

    Makes sense. I’m just auld fashioned, going extinct. It’s all too ripped and roaring for me. When young, I skewed away from critters toward botany, cuz the veg didn’t move; it was a peaceable kingdom. Alas, and now a lack, I’ve been alienated. The green symphony of millimillennium harmonic now sounds like a kuzu. And Susan Boyle has gone nutters! I feel like such a loamer at times like these. My man chester beats disunited and I go to the bars alone, aaahhhh.

    Yours erodedly,
    Mark Krueger

  8. andy June 23, 2009

    great article. pioneer species are amazing and do a great job of preparing the area for succession.

    unfortunately most people in this death culture are so used to seeing denuded ecosystems, not healthy ones, they think that is normal.

    and europe is encouraging countries to enforce legislation against invasive species – which should really be called opportunistic – which portugal seems to have embraced beyond what europe was proposing. the list of species to be banned is immense and includes the wonderful robinia pseudoacacia, dynamic accummulator and drought tolerant trees….
    which i plan to use in our forest makeover….

    oh well, not worried about something being illegal before, and too old to start now :)

  9. Quinta do Vale June 23, 2009

    They’re banning Robinia pseudoacacia?!! Por que? I’ve just bought a whole load of seeds from Agroforestry Research Trust, including some Black Locust. I’d heard several parts of Europe were experimenting with growing this tree as a crop (for all it’s obvious merits) and it’s a damn sight less flammable than Pinus pinaster or Eucalyptus globulus.

  10. andy June 24, 2009

    thats the link on expats… with a link near the beginning to the document.

    a big list of banned plants in anne 3. inc euca globulus and all acacias – mimosa. its unenforceable really, but worrying.
    robinia is a dynamic accumulator too. we plan to use lots, with chop and drop policy, to draw up and add nutrients and nitrogen to swaled hillsides.

    we recently got geoff lawtons movies – wanna come watch them? water harvesting and establishing food forest. the intro to permaculture is out soon. great stuff.

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