Farmers dread it, but ironweed is prized at garden centers


By Ted Manzer

Friday, September 15, 2017

My father-in-law would turn over in his grave. Ironweed is now a highly promoted ornamental perennial plant in many garden centers. He spent much of his life trying to get rid of it.

Ironweed is a tall perennial plant with bright purple flowers. It got its name because of the toughness of its stems. Some farmers might actually admit ironweed is a pretty plant if it didn’t take over pastures like it does.

The biggest problem with ironweed in pasture fields is that livestock won’t eat it. It’s not especially harmful to animals. It’s simply not palatable. Ironweed contains chemicals called lactones, but they must be consumed in large quantities to pose a problem.

Consequently, over time it spreads and that means ironweed plants take up more space in pastures. There’s less room for desired species that are constantly being grazed.

For dozens of decades farmers have fought this weed. They’ve clipped it. They’ve tried to grub it out. They’ve sprayed it. All methods have limited success.

There are broadleaf pesticides that will kill ironweed, but they also kill desirable pasture plants like clover and other legumes. Often reseeding of preferred forage crops is necessary.

Spot treating this weed can be effective and often eliminate the need for reseeding. However, it’s time consuming and often can’t be done while sitting on a tractor.

Ironweed spreads by seeds, so mowing plants before they go to seed can help. Plants also spread by underground stems called rhizomes. Ironweed also has an extensive fibrous root system. That makes it very tolerant of drought. In short, ironweed is one tough customer.

Ironweed is tolerant of just about every soil type. It even thrives in poorly drained and acidic soils. It grows in sun to partial shade as do most forage crops.

Unlike many problematic weedy plants, ironweed is not exotic. It’s a native plant. That’s one reason it’s gaining popularity as an ornamental. Plant breeders are developing more compact strains. Natives are all the rage right now.

I think this weed, I mean plant, has great potential for perennial gardens. I wouldn’t plant it near pastures, but it’s pretty and durable. Invasiveness is gradual, so gardeners should be able to keep it under control on a small scale. A small flower garden isn’t forty acres.

On the plus side, ironweed is a great attractor of pollinators. Bees and butterflies flock to it. Monarchs, painted ladies and tiger swallowtails are just a few of the butterflies you can see gracing the flowers.

Additionally, since livestock won’t touch it you might suspect deer and rabbits would follow suit. You’d be right. I’ve yet to see evidence of deer damage to ironweed, regardless of grazing pressure.

As is the case with many native herbs, ironweed has been used medicinally for centuries. Root concoctions have been used to regulate menstrual blood flow.

Herbalists have also prescribed ironweed to treat stomach pain and general bleeding. Root infusions supposedly help firm up loose teeth. Few side-effects have been reported. Allergic reactions causing skin irritations are possible though.

Ted Manzer teaches agriculture at Northeastern High School.