May 14, 2010

Dakota Gold: a Texas Superstar 'weed-to-riches' story

Science marries a common roadside weed and produces a 'princess'

By: Robert Burns, 903-834-6191  
COLLEGE STATION -- Dakota Gold helenium had a tough childhood. Cast into life as a common weed, it had to survive abusive Texas summers, frequent and brutal right-of-way mowings, trompings in over-grazed pastures and abandonment in empty lots.

Worse, it just got no respect, having been stuck with the ignoble name of "yellow bitterweed," said a Texas AgriLife Research horticulturist.

But along came science. One day in the mid 1990s, that same AgriLife Research horticulturist, whose name was Dr. Michael Arnold, mentioned to some of his graduate students that bitterweed, with its lovely yellow blooms, would, with a little tender, loving care, make someone a good environmentally friendly ornamental.

"In typical student fashion, they suggested we do just that," Arnold said.

Arnold and his students' work eventually resulted in Dakota Gold being named a Texas Superstar, one of five for 2010, Arnold said. After rigorous testing, AgriLife Researchers and Texas AgriLife Extension Service horticulturists designate plants as Texas Superstars that are not just beautiful but perform well for Texas consumers and growers.

Arnold's rationale for yellow bitterweed's potential was along the lines of what doesn't kill something makes it stronger. In the case of yellow bitterweed, the glaring sun and heat of Texas summers had already begun a natural selection process. Bitterweed needed little water or other resources, making it a potential low-input plant for cultivated landscapes, he said. And the frequent mowings along College Station roadside rights of way had already constituted a sort of 'un-natural' selection process for a shorter, more compact plant.

The first stage of the process was to collect a variety of plant materials.

"We basically just went around and got seeds from along different street locations where it had been mown as a roadside weed," Arnold said. "The idea was it kept the plant at a lower height so it would tend to help us get to our selection of wanting plants that had a compact low-growing habit analogous to traditional bedding plants."

Arnold and his students used a plant breeding method called "open pollination recurrent selection." This pretty much involves what the term sounds like if you give it a little thought, Arnold explained. Selected plants are grown outdoors and are allowed to be cross-pollinated by natural means, by insects or birds or the wind, bees being the most common mechanism. Crosses with favorable traits are kept; unfavorable ones rejected. The selection process is done for several seasons, about 10 years in the case of Dakota Gold.

The process has advantages and disadvantages, he said. One advantage is that it doesn't require a lot of labor. A disadvantage, particularly when the plants are grown outdoors in the region where there are plants of a related genotype, is the selections may be contaminated with the pollen of plants that have unwanted traits.

"Problem is, you'll make selections for the characteristics you want, and then the bees will bring in pollen of other plants," Arnold said.

The alternative is controlled pollination, which is usually done within a greenhouse, where bees can be excluded and the contamination prevented.

"(Controlled pollination) requires a lot of hand pollination to do that, and I didn't have the resources to do that," Arnold said.

After years of the open pollination, Arnold and his students selected plants with the low-growing, spreading habit commonly preferred for bedding plants. They also selected plants that had more flowers, another important feature for landscaping.

At this point, however, their protege was ready to graduate and make its debut into the outside world. To do so, it needed opportunities that Arnold and his students couldn't give it at the campus breeding sites, so Arnold and Texas A&M licensed the improved breeding lines to Ball Horticultural Co., an international company that does business in 20 countries.

Ball Horticultural further improved the lines, and did so in only two years. The company could do this, Arnold said, not only because it had more resources, but because it had breeding sites far removed from the plant's native habitat of Central Texas. This meant there was little danger of the improved breeding lines being contaminated by the pollen of wild cousins.

Ball also found, Arnold said, that Dakota Gold did quite well outside of Texas. It was grown successfully as far south as Florida and as far north as Chicago.

Another requirement for Texas Superstars is that they be easy to propagate. The rationale for this is if AgriLife Research and s AgriLife Extension horticulturists are going to promote a new cultivar to the general public, there must be enough plants at a reasonable price to meet the demand, Arnold said.

"For greenhouse and nursery producers, it is important to grow Dakota Gold in a light substrate with good drainage that does not contain large proportions of peat moss," Arnold noted in his official report.

For home landscapers, it is just as important not to overwater. Because of its beginnings, the plant likes lots of sunshine and tolerates heat very well.

"So pick a sunny spot for her," he said.

Unlike its roughshod cousins, Dakota Gold helenium will initially grow as "a tight, flattened rosette of coarse foliage," Arnold said. Later, it becomes more erect and the foliage more "highly divided and finely textured" as it puts up flower stalks.

As it matures, Dakota Gold helenium turns into a real 'princess' of a bedding plant, with a gown of dark, green circular foliage 12-18 inches in diameter, and crowned with bright yellow flowers that are reminiscent of daisies, he said.

Texas Superstar is a registered trademark owned by AgriLife Research.

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