A short while ago I wrote a blog post about how happy I am that my cows and sheep are finally running in a big enough group to do appreciable damage to the burdock and parsnip stands in various parts of my pastures. This post is about about two other members of the Asteraceae (Aster family). This morning I moved the flerd (sheep FLock + cattle hERD) into a daily allocation of grass with a good size stand of thistles. These spiny warrior plants are aggressive colonizers of bare ground. On my farm they follow the pigs by a season or two and they also sometimes get a strong foothold where I feed hay to the cattle. Cows are heavy and can break grass roots apart if they're concentrated around a bale for hours under certain conditions. They'll cause enough damage to the sod that the thistles can become a dominant plant. Since I have a nice size herd of pigs that like to root things up and feed plenty of hay during the winter, I have several places on my farm with concentrations of thistles. Bull thistles (seen to the right of the steer above) don't stress me out at all. They're biennial which means they have a two year life cycle and then they're dead and gone. Year 1 they grow with a lower rosette form and then in year 2 they send up a 6, 7, or 8 foot tall stalk with flowers and branches. They're gnarly to walk past at this stage. Even the thick hided cattle tend to avoid them for the most part once they've built a stalk and have their million points at the ready. But I don't worry about them because a thick patch typically reverts to grass the subsequent year. And they have big, deep reaching roots that scavange minerals and nutrients from far down in the soil profile. And they're clearly amazing bee plants. Every time I walk past bull thistles in bloom I hear an incessant buzz of bees.
With all the negative news I hear and read about colony collapse disorder, mites, and other problems facing honey bees, I like to feel like I can do something to create habitat they need. If I were a row crop farmer I'd probably have different opinions about the relative merits of letting bull thistles grow on 1/10,000 of my total acerage, but I keep livestock not corn and don't see any reason to mow the bull thistles at this time.
Canada thistle is more of a mystery to me. It's perennial, and rhizomatous (spreads by roots), so allowing it to really take over a given piece of ground is more vexing than bull thistles. With bull thistles' short life cycle I know it doesn't mean a long-term loss of production from the area I give over to bug habitat. The thing I can't figure out about Canada thistle is what prompts it to grow vigorously year-over-year in one place, and then 200 yards away another near monoculture of the stuff one year will be virtually gone the next. It might be mowing at an opportune time that stunts it (I've mowed some during flowering), but I kind of doubt that is the primary signal for the plant to senesce. I had an invading patch by the garden in 2016 & 2017 and this year there's almost none of it left. I planted some Jerusalem Artichokes in amongst the thistles to see if the chokes could over-top the thistles, and they sure have. I can barely find a prickly leaf anywhere. In the pasture I've observed similar things. Strong stands this year will be virtually gone the next in one place while another patch comes roaring back in full bore + 30% year over year. If any of you dear readers have further information for me about Canada thistle I'd love to be educated more fully on the growth habits of this plant.
Maybe I just need more pigs to solve my Canada Thistle conundrum. These pigs didn't need any training at all to eat up. They took it upon themselves to first graze the leaves down and then dig up the roots and eat them too. Note this video is from June when the thistles had more leaf relative to stalk. But still, if you watch closely you'll see the pigs don't like chewing on the leaves very much. There must be some good feed value in them though or they wouldn't bother at all.
Photo and Video Credits - Edmund Brown