Invasive flower threatens Texas bluebonnets from wide swaths of the state

POSTED: Sunday, April 1, 2012 - 6:30pm

UPDATED: Sunday, April 1, 2012 - 6:34pm

A quarter of a mile west of the gate of the Lady Bird Johnson Wildflower Center in South Austin, invasive plant expert Damon Waitt steps on a small shovel.

He's showing a TV news crew how to dig up a plant loaded with small but pretty yellow blooms on the side of the road.

As he pushes with his foot, the shovel handle breaks off.

Everybody laughs, including Waitt.

That, as it turns out, is the only thing funny about bastard cabbage.

"What happens," Waitt said, "is that in the fall when these plants germinate, they form a rosette close to the ground, and that rosette actually takes up space and blocks out the bluebonnets that should be coming up in that area."

The result is a slow-but-steady vanishing of Texas bluebonnets from wide swaths of the state.

"I've noticed," Waitt went on, "over the last few years, large patches of bluebonnets succumbing to bastard cabbage. It is literally out competing the bluebonnet and our other Texas wildflowers for resources. This is not just an Austin problem; I've seen this everywhere. I just drove back from Port Aransas a couple of weekends ago. It was all along the highway from Port A to Austin."

So how did this happen?

"We call it bastard cabbage," Waitt explained. "It's also known as Mediterranean Mustard. It's actually native to the Mediterranean region: Northern Africa, Central Europe.

"How it actually came to the United States is a little bit unclear, but we do know how it spreads. It's spread when it goes to seed; mowers chop it up and spread the seed. But then also, the seed is very small like a rye grass seed, and so it actually gets distributed along with rye grass seed."

So what's to be done?

The answer to that question is complicated.

"The best way to get rid of it is to manually remove it," said Waitt. "You can hand-pull it if the ground is soft enough. Otherwise, use a small shovel.

"The plant has a nice robust tap root and you want to make sure you get that because if you don't get that, the plant will continue to grow and reflower."

Even if you do get the tap root, the bastard cabbage can still come back.

That's because seeds from previous growth lie in the soil below, ready to sprout and start new plants.

That explains what researchers discover when they experiment with herbicide treatments.

The poison does kill the plants, but the seeds in the ground resprout and the infestation comes back stronger than ever."

At the Wildflower Center, Waitt and other researchers have had some luck with a more organic approach.

"We tried over-sowing the bastard cabbage field with vast quantities of wildflower seeds," he said. "We were actually able to show that Indian blanket, if there's enough seed out there, can actually compete with bastard cabbage.

"So that's a very natural way that we can try maybe to deal with this situation," he said.

A successful program, though, will take far more than that.

"I encourage universities to start doing research on the best ways to manage and control this," Waitt said. "I would encourage our highway department to think about establishing a control and management program for it. And I would encourage citizens to get out there and start pulling it."

Waitt is clearly worried.

"On a scale of 1-to-10," he said, "I'm at about 9.5 right now. If we don't do something about this, we're going to have to say goodbye to our Texas wildflowers, including bluebonnets. We're not going to lose every bluebonnet. I don't think people would ever let that happen in the state of Texas, but I am saying that among all of the invasive plant species problems that we're facing in the state, things like giant salvinia and hydrilla , the bastard cabbage should be up there in the top 10 invasive species we really need to be thinking about how we're going to deal with."

Meanwhile, back at Waitt's office, the phone rings regularly.

"We get calls from people asking, 'Where can I buy seed for that beautiful yellow wildflower?'"

Clearly, there is lots of work to do.
 

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