In the United States and Canada, 210 kinds of orchids grow in climates as diverse as Hawaii's lush tropics and Canada's forests. Half are native to Florida.

Of these 210 varieties, 41 are endangered or critically threatened, according to the Center for Plant Conservation in St. Louis. An endangered species is one that is in danger of becoming extinct, while a threatened species is rare and may become endangered.

Little is known about orchids; only a handful of researchers worldwide study the delicate-looking plants, says Lucile McCook, horticultural taxonomist at the Missouri Botanical Garden in St. Louis. One reason is that they are difficult to work with.

"We know so little about trying to grow them, reintroduce them," she says. "We are lacking in basic natural history information so often, and that's true with all the plants, but it's triply true with the orchids."

In addition, many people don't specialize in orchids because of the time it takes to complete a research project. "If somebody gives you money to do research, they want results in a couple of years, and these are long-term projects, in some cases lifetime projects."

Botanists in the US are closely watching the Kew (Royal Botanic Gardens near London) efforts to reintroduce the yellow lady's slipper and other orchids, Dr. McCook says.

In the US, several varieties of yellow lady's slipper exist. While certain varieties are endangered in some states, the lady's slipper is not on a national list of endangered orchids.

All plants on public land that are threatened or endangered in the US are protected under the Endangered Species Act. States also have their own lists for plants that are in danger of extinction.

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