Star Thistle.

A.V. Walters–

spotted knapweed 2

“Star Thistle”

See the lovely fields of purple flowers, rippling in the wind. Taste the delicate flavors, the floral back-notes in the honey from these “local” fields.

The real name for this heralded bloom is spotted knapweed, and it’s no local. Conservationists call it an invasive species, originally from Eastern Europe. Once it gets its roots into your soils, it never lets go. Nobody talks about eradication; they only talk about “management.” There was spotted knapweed on our property before I bought it, decades ago, so I shouldn’t complain. Only recently, though, have I learned about its evil and pernicious ways.

In a riff on Irish luck, Rick and I used to joke that it weren’t for spotted knapweed, we’d have no weeds at all. Little did we know we had that backwards. Sure, we have poor glacial soils, but the more potent force of our limited landscape is spotted knapweed. You see, not only is it a vigorous invasive, but it has the admirably devious survival mechanism of poisoning the soils around it so little else will grow. It is an expert in plant hegemony.

So that would explain our spindly vegetable garden! We have acres of knapweed.

Knapweed has a multifold program of engagement. First, it is a vigorous competitor. It sports a thick absorbent taproot that quickly captures and stores any available water (leaving its neighbors thirsty.) It is a rampant reproducer, colonizing both via ample seed production and from runners from its rhizome root system. If you try to remove it, and leave any part of the rhizome in the soil, it will sprout and flourish, like the cursed broom in Fantasia. Knapweed avoids predation by being the most bitter plant in the field. (Even goats avoid it; though I understand that sheep will eat it.) Back in California we used goats to clear poison oak from the hillsides, but even the goats are too picky to mess with the spotted knapweed. If that weren’t enough, knapweed generates its own phytotoxins, literally poisoning the soil around it. The mechanism of its catechin toxins aren’t well understood, but they prevent germination of competing seeds and poison the root zone. When a knapweed root comes in contact with the root tips of another plant, it sends a cascade of chemical messages to its victim, triggering apoptosis, or programmed cell death, from the roots, on up.

Presumably, back in Eastern Europe, spotted knapweed needed these strategies to survive. Plants from there have immunities that can withstand its chemical onslaught. Here, though, our native plants and crops have few defenses. It’s a problem from coast to coast—but especially so in the dry rangelands of the west.

But the bees love it. It’s one of the few flowering plants that continues to bloom and provide nectar in the dog-days of August. I have beekeeper friends who react with open hostility when folks discuss ways to eradicate knapweed. The honey produced from knapweed blooms is so delicious that “Star Thistle” is treated as a premium appellation product, like Locust Honey, or Tupelo.

I’m a beekeeper, but I’m also a gardener. Would a rose, by any other name, smell as sweet? A pest is a pest is a pest is a… (my apologies to Gertrude Stein.)

Star Thistle, my ass.

spotted knapweed 1

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