This photo shows the impact of late summer/fall mowing on Goldenrod. To the right, the headland of this field was mowed the previous year for hay in June. To the left, it was knocked down in late August, encouraging goldenrod to break dormancy and produce stalks. Note the dark green clumps of goldenrod clones emerging on the left side of the photo.
For years it was just part of the scenery, a minor weed loitering in ditches and headlands. But of course, that’s what goldenrod wants you to think.
The truth hit me one day in the back pasture, when, glancing over my shoulder, I thought ‘Hey, where did all this goldenrod come from?’
Suddenly it was as if the yellow-headed hordes were mounting a slow-motion takeover, closing in
The villain: Canada Goldenrod
with grasping, claw-like rhizomes, and . . . Yikes! Maybe this is the pasture version of a B grade horror flick, and I’m the hapless victim.
If goldenrod isn’t a problem on your farm, chances are you have your own zombie weed − one that eats your profit and refuses to die. As the weed shuffles across the pasture, will you be the hero who survives until the credits, or the guy who, early in the flick, goes down into the cellar without a flashlight to check out that “odd noise”?
Read on to defend yourself:
- All seems quiet, and then . . . they’re everywhere!
Canada goldenrod (Solidago canadensis) doesn’t just parachute downy seeds onto bare soil. It spreads underground, fed by roots that can reach 3.5 metres deep in a tall grass prairie. Most clumps of goldenrod are actually clones of a single plant, able to persist for decades and in some cases, more than a century.
In short, this member of the aster family may be underground, but . . . it’s not dead. Goldenrod’s “rhizomes can stay dormant under the soil for a very long period of time,” says Ontario Ministry of Agriculture, Food and Rural Affairs weed specialist, Mike Cowbrough “But as soon as you disturb the area and then leave it fallow, one of the first species to populate the area is goldenrod.”
- You can’t kill them! (At least, not in the first half of the movie.)
Like Hollywood monsters, Canada goldenrod is not only tough to kill, it’s endowed with special powers. Because it produces chemical compounds that suppress the growth of other plants (and make its own leaves and stem unpalatable) it has a sort of “force field” to fend off competing plants and deter some grazing animals. And in case you want to come after it with torches and pitchforks, it actually likes fire.
Equally scary, when you hack it down, it grows better. Late summer and autumn mowing reanimates dormant rhizomes, encouraging them to turn skyward, emerge from the soil and sprout a cluster or “rosette” of leaves. The next spring that rosette will launch a new stalk, and you get just what you didn’t want − more clones.
- Wait, maybe you’re the bad guy.
Plot twist folks: what if the people are bad and the monster is good? (Or at least misunderstood?)
Leaving aside its debits as a forage for livestock, goldenrod is a major source of nectar and habitat for insects including pollinators. In 1948 a researcher counted insects using a goldenrod patch during the course of a year and catalogued an astounding 241 different species. (Also in the plant’s favour: it doesn’t trigger allergies.)
“Goldenrods are one of the components of tall grass prairies in Ontario,” says Wasyl Bakowsky, a vegetation ecologist with the Ontario Ministry of Natural Resources. Unlike the bromes, Timothy or bluegrasses farmers have introduced to Canada, native grasses have evolved to coexist with goldenrod. That’s why the perennial “never forms massive clumps or spreads in tallgrass prairie,” Bakowsky adds. “I only see large spreads in uncultivated fields, which have a high component of introduced species present.”
- Help! You need the advice of a scientist! (Or at least an actor in a white coat.)
If there’s one benefit from a misspent youth watching old movies, it’s realizing that whenever zombies, aliens or giant lizards go on the rampage, you need a scientist to provide a tidy explanation. Maybe nuclear testing has created giant mutant ants, (Them!) or the aliens want our water (Battle: Los Angeles) or a returning space probe has blown up in the atmosphere, bringing the dead to life. (Night of the Living Dead, and okay, that one strains credibility.) By analysing the cause of the problem, the scientist usually pinpoints the invader’s weakness.
In my case, the guy in the white coat is Jack Kyle, grazing and pasture specialist with Gallagher’s Passion for Pasture program. Kyle noted the fields with the biggest goldenrod problems were also ones where I’d changed my management, as part of an effort to fight sheep parasites (and that, by the way, is another horror movie).
When I went from relatively intense production (cutting or grazing fields two or three times per season) to a single cut or grazing pass, the goldenrod was set free. To make things worse, a couple of wet years forced me to delay the first hay cut until late August, fueling goldenrod’s expansion by forcing rhizomes out of dormancy. Within a few years, it was a regular goldenrod apocalypse. Even the neighbours started to notice.
- Only you have the antidote.
It’s tempting to nuke the invaders, but another movie lesson is brute force can backfire. (As in Independence Day, maybe you’ll just flatten Houston and make the aliens really mad.)
Instead I’m taking a less costly (and admittedly less cinematic) approach: cutting and grazing more often. As Manitoba Agriculture’s Weed Control in Pastures recommends, allowing goldenrod “to regrow to 8 to 12 inches between mowing will eventually kill these plants.” To boost competition against the weeds, I’ll also be looking for ways to improve soil fertility and pH, and add more friendly legumes by frost-seeding.
Why not use tillage or herbicides? That may be an option on your farm, especially if you have a regular crop rotation. In my case the problem fields are hilly, with deposits of sand and gravel that make for tough ploughing and easy erosion. And I lack a sprayer, so if weed control requires more than spot-spraying or hand-pulling, the default option is grazing and cutting.
“I think you could do a fair bit of control with grazing management. With really high stock density you might be able to trample it down. Over a period of time it will vanish on you,” Jack Kyle predicts. “Between hay cutting and grazing and maybe spraying and frost seeding, in three years I think you’d be ahead of where you’d be with ploughing, at a lower cost.
As Alexander “Sandy” Smart, a South Dakota State University rangeland specialist says, ranchers tend to get worked up about goldenrod because it often looks worse than it really is. But when Smart looked closely, he found Canada Goldenrod may not be a significant yield robber. Thanks to its deep roots, it may get most of its water and nutrients from deeper soils, rather than thieving from its grassy neighbours. “It might look bad, but it could be that goldenrod is really only covering one per cent” of your pasture, Smart says. Rather than ponying up for an aerial herbicide, “you’d be better off at buying some hay.”
So I’m not out to kill every last goldenrod − just reduce it to a level the neighbours won’t mention. (I hope.)
But to avoid future problems, vigilance will be the key. After all, most of the bad things that happen in monster movies happen to folks who aren’t paying attention in the first 15 or 20 minutes. If you’re really serious about heading off a zombie weed apocalypse, your best weapon is − you got it − your brraiins.
— Ray Ford