Tuesday, November 24, 2009


The above graph nicely illustrates what we're up against when it comes to invasive plants. A few species of highly adapted superweeds are being transported across oceans at unprecedented rates. The California Invasive Plants Council estimates that CA spends a minimum of $82million a year on attempting to control these runaway armies of leafy terrorists with very limited success. The plants continue to spread and new species are regularly introduced despite valiant efforts to intercept these illegals at CA's borders ("Any fresh fruits, vegetables, or living plants with you today?")

The top dozen most wanted weeds in california?

Aegilops triuncialis - barb goatgrass
Bromus madritensis ssp. rubens - red brome
Centaurea maculosa - spotted knapweed
Centaurea solstitialis - yellow starthistle
Cortaderia selloana - pampasgrass
Cytisus scoparius - Scotch broom
Delairea odorata - Cape-ivy, German-ivy
Euphorbia esula - leafy spurge
Foeniculum vulgare - fennel
Genista monspessulana - French broom
Hedera helix, H. canariensis - English ivy, Algerian ivy
Lepidium latifolium - perennial pepperweed

in urban areas these are the plants the colonize the cracks and margins where maintenance is minimal. Once established, these plants can be impossible to eradicate. Many of the plants will readily grow in the rugose spaces of architecture and infrastructure, often at edges, seams, or material transitions where an interruption in the impermeable cap creates a micro-swale for collecting nutrients and water. As the plant grows the expansion of roots, stems, and leaves act like small hydraulic jacks slowly and inevitably pushing aside the built environment to increase the potential for growth, survival, and reproduction. The forces at work are enormous, the sun pump driving massive disintegration of urban spaces through the microscopic multiplication of meristematic tissue. If we stopped our constant hacking, poisoning, mowing, pulling, and burning a handful of feral plants would quickly engulf our homes and cities, attacking walls, roofs, rafters, roads, bridges, skyscrapers, freeways, gardens... a smooth green skin appliqued to the city's

so how do we stop them?

A few options:
manual control: expensive, time consuming, hard, and effective
fire control: dangerous, many invasives surive or are encouraged by fire
chemical control: cheap, fast, easy, and completely ineffective.

broad spectrum herbicide applications for the control of invasive plant species poses the same risks overreliance on antiobiotics does; namely the inevitability of breeding resistance into the target population. This is readily observed in the proliferation of Roundup resistant weeds in areas that rely on Monsanto for their genetically modified herbicide resistant crops. (another reason to buy organic... less risk of GMOs)

the good folks at grist bring us this:

"In the U.S. alone, glyphosate use jumped by a factor of 15 between 1994 and 2005, CFS claims. And this herbicide gusher has given rise to a host of "superweeds" -- weeds that tolerate heavy doses glyphosate. How do farmers deal with superweeds? By jacking up the dose of glyphosate"

Glyphosate... (key ingredient in Roundup) better than atrazine right? Sure, but that's like saying a Hummer is better for the environment than a Hummer limo, not inaccurate but not entirely true. Wikipedia summarizes.
I'm most interested in this paper which suggests that glyphosate may inhibit the ability of soil microbes to protect plants against pathogens, causing higher incidence of plant diseases in fields treated sprayed with Monsanto's magic SAFE weed killer.

uh oh...

There are now confirmed cases of herbicide resistant weeds in 13 states, reporting a total of 63 different weed species. At this rate Roundup ready crops will be completely useless despite the millions of gallons of glyphosate saturating our soil. This points to a larger problem of herbicide resistance in invasive plants and suggests that it's only a matter of time before English Ivy, pampas grass, and japanese knotweed figure out our chemical tricks.

I imagined a sort of high-tech government facility deep in the Ozarks where top-notch plant breeders are hard at work developing the most virulent and unstoppable weeds imaginable. The vigor of Arundo donax, the taproot of knapweed, the rhizome of bamboo, the seeds of a thistle, the thorns of himalayan blackberry, the roundup resistance of Monsanto's weeds, and the speed of kudzu.
Weaponized weeds.

So what can we d0?
biomass production seems like an obvious solution. these plants can be converted into compost or energy (or both via biochar) and used to increase soil fertility in the degraded zones that often have both the absence of maintenance and competition that incubate these over-zealous castaways.

(example showing Jean Pain's biomass experiments)

This requires, like always, a ton of maintenance and given the tendency for machines to make the problem worse via incomplete removal and meristem shattering, it will probably have to be done the old fashioned way, by hand. This, of course, is radically expensive and would seem to encourage more creative incentives for invasive control, such as exchanging space for time (the homestead approach).

There is the possibility that the proliferation of exotic invaders that destroy our human-made environment are a sort of built-in mechanism for biosphere regulation. Invasive plants are the land's attempt at fighting back against the suffocating cap of impervious surface, a bioclimatic reflex. Combined with crazy rasberry ants: eating electrical devices throughout the southern U.S.(!), H1N1, and zebra mussels it would appear that the control we believe we have over our environment is a wayward delusion persisting from the mechanistic roots of enlightenment science. Maximum control only pushes the inherent energy of the system into other channels (why fences are always hopped). We exist at the mercy of our fellow lifeforms and rather than fighting them we need to focus more of our energy towards developing complex probiotic solutions to our abiotic actions.


Forge Ahead Puppet {BUILDING} Productions said...


it's been years since i read this article in full, but i must pass it on to you now in case you haven't read it before, i think it's get some things stirred up: http://www.wired.com/wired/archive/8.04/joy_pr.html


Anonymous said...

ew. and now there's the environmentally friendly "glyphomate," with residual fungi-killing formaldahyde.

aren't "weeds" just whatever we decide to be "unwanted plants." putting these plants to good use is key. compost, pest distraction, subsoil mineral transport, root mass fungal life, food, medicine!

have you read "Weeds: Guardians of Our Soil?" it's oldschool. can be read online here http://www.journeytoforever.org/farm_library/weeds/WeedsToC.html

Nathan R. Hodges said...

yeah, i talked about the cultural aspects of weed in "on weeds" a while back, and while i agree that many of the plants we commonly call weeds are invaluable resources in the healthy productive biotic landsape, there might be some weeds that are too powerful, too aggressive, and too allelopathic to be a positive force without constant vigilance & lots of labor. by lumping all weeds as either good or bad i think we miss an important point about the fundamental changes humans have created in their environment and how traditional views on ecosystem management might be ill-equipped to deal with some of the potentially game-changing developments, that is after a system has gone through collapse and reorganization into a functionally different state do the old, pre-collapse rules still apply?

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Milan Young said...

Our Oregon farm is infested with spotted knapweed (northern cousin of star-thistle). On steep slopes we were able to control it by covering the area with a tarp for a couple years followed by a well timed planting of an aggressive cover. This takes the area out of "production", but it holds wildlife benefiting the farm in other ways.

On larger flat areas, we found tillage, propane burning, and cover crops worked well. But it's expensive, and I'm having second thoughts on whether this level of fosile fuel usage should be classified "organic".

The approach I like the best, is to "join 'em". Turns out knapweed contains about 18% protein, and animals can be trained to graze it during the winter season. Add to this the fact that it's hardy and self seeding, and you have almost the perfect crop for winter paddocks.

One last comment before I end my weed discussion. I've noticed in recent years an explosion of the number of weevils in our fields. At first I thought it was pollinating the knapweed, but I now realize that it is attacking the young flowers. These are the simple sort of solutions that nature produces if we just give it time and stay away from chemicals. It's not that I'm totally against chemical warfare, but it needs to be viewed as a tool rather than the solution.