Missouri Botanical Garden preserves, restores local plant life
This article first appeared in the St. Louis Beacon, Nov. 5, 2009 - When we think of rare and endangered plants, many of us tend to assume they are all in tropical rain forests. Not so. Rare plants from our area -- and indeed all over the United States -- are in danger of disappearing forever.
Sometimes housing developments destroy a plot of plants that grow only on a rocky outcrop called a glade. The white-haired goldenrod grows only under cave-like overhangs in Kentucky and Tennessee. Rock-climbers and hikers tend to trample it. Climate change may already be having a profound effect on plant survival.
Matthew Albrecht, assistant curator of conservation biology at the Missouri Botanical Garden, collects and preserves seeds from 27 of these rare and endangered species in the lower Midwest. Seed-banking is part of his work as Garden liaison to the Center for Plant Conservation, an independent national network of 34 botanical institutions dedicated to preserving threatened plants.
Seeds are stored both at each regional center and at the USDA seed bank in Fort Collins, Colo. Collectively, this National Collection of Endangered Plants is the largest living (seed and material) collection of endangered plants in the world. It preserves material from about 700 species.
The Garden takes a two-pronged approach to conservation:
- Preserving plants in their native habitat is termed "in situ."
- Preserving plants off-site is called "ex-situ."
Seed banking is "ex-situ."
Ex-situ conservation involves not only collecting and storing seeds, but learning how to propagate them, working with land management agencies to conserve natural populations and reintroducing them back into the wild.
Collecting and preserving these plants over an 11-state area is a daunting task. The collection has to be timed precisely. If Albrecht and co-workers get to a site too early, the seeds won't be ripe. But if they are too late, all the seeds might already be eaten or dispersed. Then of course, the plants might be rare simply because they don't produce much seed. Collecting is a multi-year process.
Once back at the Garden, seeds have to be cleaned, dried, sealed into labeled waterproof packets and frozen. This is hand work.
Collecting seeds is just the beginning of Albrecht's work. Since one of his obligations is to propagate seeds, he goes to the lab. Most native Midwestern seeds are dormant when dispersed from the plant and require some sort of environmental jolt to break their dormancy.
Many seeds have a coat that is physically impermeable to water or gas. Before a seed can germinate, the coat must be broken down.
- Scarring the seed with sandpaper breaks the coat.
- Repeated extreme temperature fluctuation may stimulate a breakdown.
- Fire breaks the dormancy of many prairie plants; hence the profusion of flowers the season after a controlled burn.
- Other seeds are sensitive to light, and need to be exposed to the red end of the light spectrum to germinate. If they are buried in the soil, they won't sprout until the soil is disturbed and the seeds are brought to the surface.
- Still others need a specific temperature cycle.
Albrecht gives the example of bloodroot, a Missouri native that blooms in the early spring. Its seed matures and disperses in June. It won't germinate until fall, however, because it needs a hot cycle followed by cooling. Even then, it will only form roots. It can't send out shoots until the spring, because first it needs to be exposed to winter cold. In other words, bloodroot is a plant of all seasons.
Because of all this variety, the Garden seed bank has incubators where seeds are rotated through different temperature, moisture and light conditions to find their germination requirements.
When Albrecht finds out how to get seeds from these endangered plants to germinate and make seedlings, the next step is reintroduction into the wild. Success can be elusive.
Pyne's ground plum, is known only in five locations. In 2001, about 100 seedlings grown in MoBot greenhouses were planted in a cedar glade in Stones River National Historical Site in Tennessee. After three years, everything seemed great; the ground plums were sexually reproducing, and naturalists even observed a seedling. But that was the last year the plants made seeds, and by this summer only three plants remained.
Albrecht is hoping for better success with another rare species he has learned to grow. Claytonia ozarkensis grows only in the cracks of limestone and sandstone bluffs. Always rare, it has been made rarer still by dam construction that put its habitat under water.
He plans to transplant some of his seedlings to bluffs in Shaw Nature Reserve. Because it is very closely related to the common Spring Beauty that grows everywhere, he will transplant some seedlings into the woods to try to figure out why it is so limited in its habitat.
Perhaps this lovely flower will grow in Shaw Nature Reserve. Almost 1,000 species of native plants do. The only endangered species are experimental plantings by Albrecht and his associates.
The Nature Reserve is dedicated to returning the land to its condition before European-style agriculture, according to James Trager, restoration specialist. Formerly known as Shaw Arboretum, these 2,500 acres in Gray Summit housed many of the Garden's specimen trees.
It was established in 1925 when coal smoke polluted St. Louis so badly that plant collections were threatened. Today, thanks to vastly improved air quality, the Reserve is not needed as a refuge. It is an educational and recreational facility dedicated to habitat restoration.
The biggest tool in restoration of forest, prairie and glade is fire. Native Americans used annual fires for landscape control and hunting, said Trager.
With regular burning, the fires don't get too hot, and the trees are unaffected or just mildly scorched. The resulting oak-hickory forest is open, with lots of mixed native species growing under the trees. Most Missouri forests are second-growth forests with a dense overhead canopy under which nothing can grow and about a foot of leaf litter.
Fire also lays the groundwork for prairie restoration and maintenance. To restore some acreage into prairie, Trager and his associates bulldozed the invasive native cedars and burned the fields. Then they sowed a mixture of about 60 native grassland species on the bare ground and let them grow. When the prairie restoration began, they had to use some purchased seeds. Since then, all mixes are made with seeds hand-collected within about an hour's drive. They are matched habitat for habitat.
"Little bluestem, the most widely distributed grass in North America, grows in more than one environment. So when we are restoring a prairie, we collect little bluestem grass from prairie," said Trager. "When we do glade restoration, we collect little bluestem from glades."
Glades are the "crown jewels" of habitat preservation at the nature reserve. Glades are sunny areas where rock is at the surface, so the land can't be used for crops. In the glades are a great diversity of plant species, most of which are not found elsewhere in the reserve. Glades can be grazed, and overgrazing creates opportunity for the cedar to move in.
Trager pointed out that as you drive the highways in the fall, and see dark green patches among the reds and yellow, they are probably overgrazed glades in which cedars have crowded out the true glade flora.
Shaw Nature Reserve is a living museum of native plant associations. These associations include animal life like the birds and insects that live with and use these plants. When any plant species becomes endangered, diversity is lost and it is impossible to predict the effect of that loss.
Both the restoration and preservation research work toward the same goal of maintaining ecological equilibrium.
Jo Seltzer is a freelance writer with more than 30 years on the research faculty at the Washington University School of Medicine and seven years teaching tech writing at WU's engineering school.