"It turns out that the good weather conditions that give us good wildflower seasons also favor the bastard cabbage," said Damon Waitt, senior director and botanist at the Lady Bird Johnson Wildflower Center.
"I've seen areas that used to be bluebonnet hillsides along roadways that are now bastard cabbage hillsides," he said.
Waitt said it's not known exactly when or where or how the invasive weed with the scientific name of Rapistrum rugosum got introduced to Texas, but it may have happened when the seed of the weed native to the Mediterranean area got mixed in with grass seeds.
He said bastard cabbage's proliferation in Texas has gotten worse in recent years. He said bastard cabbage -- which though part of the mustard family resembles broccoli or cabbage plants because of the flowers at its tips -- is growing everywhere this year from parks to front lawns, but is especially prevalent along the state's major roadways.
Waitt says most wildflowers grow as tall as 1 to 2 feet. Bastard cabbage grows anywhere from 2 to 5 feet tall.
"We've seen more of it this year than we ever have," Dennis Markwardt, director of vegetation management for the Texas Department of Transportation.
Markwardt said bastard cabbage was able to make headway across Texas because so much grass was lost last year in the drought. And its proliferation is also making it hard for the grasses to re-establish.
The same mild winter and well-timed rains that led to a good wildflower showing across parts of the state this spring also helped the bastard cabbage multiply.
"It's perfect growing conditions for them. And that's why you're seeing it just everywhere. In every over-grazed field, everywhere there's been soil disturbance," said Markwardt, adding, "It is uncommon to see it this thick, but it doesn't really surprise me."
He said they're researching now how to use herbicides to tackle the bastard cabbage problem in the fall when they will begin to grow again. And while that might kill off wildflowers germinating at the same time, he said the roadsides have a good enough seedbed to rebound with more wildflowers. And, he said, they can replant wildflowers where they need to.
"We going to make sure we can find a way to keep this under control," he said.
He said that they are currently doing spot mowing and herbicide treatments to get rid of bastard cabbage growths in places where they could cause traffic safety problems.
"If somebody's trying to pull out on a divided highway or cross a median and they don't have the sight distance, it can cause a safety problem," Markwardt said.
Waitt said that where it's feasible to put in the manpower, the bastard cabbage can also be eliminated by digging it up and throwing it away in a sealed trash bag.
Waitt said evidence of the good wildflower season that came as a result of well-timed rains in the fall and winter can still be seen -- especially if one gets off the main roads.
"There's some amazing, amazing shows in the less-traveled regions of the state," Waitt said. "You can still get out there and see good bluebonnet and Indian paintbrush displays."
He said bluebonnets usually peak by mid-April, though they may peak earlier. The wildflower season should last into June, with Indian blanket, coreopsis and sunflowers hitting their stride.
And, even with bastard cabbage causing problems in areas, Texas is still having a much better season that last year's, which was dismal as Texas endured it's driest year on record.
"In view of last year, how bad the drought was and how brown everything was, people are going, `Hey, this is wonderful compared to what we had last year," Markwardt said.
