Hemp is not marijuana, but its resemblance to its cannabis cousin has kept the plant banned in the United States for decades despite many uses for textiles, food, cosmetics and other purposes.
Now, hemp is getting support from US lawmakers and others who argue legalization of industrial hemp would have broad economic benefits.
The plant provides seeds rich in protein and nutritious Omega-3 fats. Its oils are useful for cosmetics and cleaning products, and its fibers are used for rope, clothing, auto body panels and building materials. Hemp also has potential as a biofuel to replace petroleum.
But hemp's future has been clouded by the movement to legalize marijuana for medical purposes, which has succeeded in several states, even though hemp advocates argue that the two issues are unrelated.
Some say the marijuana effort has hurt the movement to legalize industrial hemp, which is a member of the cannabis sativa family but without the active narcotic ingredient that characterizes marijuana.
"The biggest misconception is that if you allow hemp farming you are allowing marijuana farming," said Adam Eidinger, a spokesman for Vote Hemp, the lobbying arm for the US hemp industry, and owner of a store in the US capital selling hemp products.
"This is an agricultural issue ... We think there is a billion-dollar crop being kept out of the hands of farmers by the government."
In Congress, some two dozen lawmakers are sponsoring a bill to reverse the ban on industrial hemp. The measure was introduced by Representative Barney Frank, the powerful head of the financial services committee, and Ron Paul, a libertarian on the other end of the political spectrum.
Paul said recently that US policy mistakenly lumps hemp with marijuana even though the former contains less than 0.3 percent THC, the psychoactive chemical found in marijuana.
"Nobody can be psychologically affected by consuming industrial hemp," he said.
"Unfortunately, because of a federal policy that does not distinguish between growing industrial hemp and growing marijuana, all hemp products and materials must be imported. The result is high prices, outsourced jobs, and lost opportunities for American manufacturing."
The Hemp Industries Association, a trade group involving US retailers and makers of hemp products, estimates that hemp food, vitamin and body care product sales to be in the range of 113-129 million dollars for 2009.
Adding in other uses, the total hemp industry may be worth as much as 400 million dollars in the United States, the group says.
Because hemp products can be sold legally but hemp plants cannot be grown in the US, most of the plant materials are imported from Canada, France, China and other countries, the association says.
The industry group, which won a lawsuit in 2005 against the government on the legality of hemp products, now wants the administration of President Barack Obama to clarify that hemp plants are legal as well.
The group declared the week of May 17-23 Hemp History Week, to draw attention to historical uses of hemp over thousands of years as well as its future potential.
Members point out that the plant has been cultivated for 10,000 years and among its early uses was canvas -- a word derived from cannabis -- for fabric and sails.
The Declaration of Independence was printed on hemp paper, and the first American flag was made with hemp fiber. American founding fathers George Washington and Thomas Jefferson grew hemp.
During World War II, the US government ended the ban and encouraged farmers to produce hemp for the war effort, before effectively outlawing it again under the 1970 Controlled Substances Act.
It is possible to grow hemp with a permit from the US Drug Enforcement Administration, but in practice the government rarely grants these, say hemp advocates.
David Monson, a farmer in North Dakota who is also speaker of that state's House of Representatives, filed an appeal in US court alleging that the DEA delayed the approval an application for more than three years. DEA declined to comment on the case, citing ongoing litigation.
"We want to them to clarify that growing hemp is not a crime," said Eidinger. "Right now medical marijuana is more legal than non-drug hemp."
But Eidinger said hemp backers are optimistic about getting support from Congress and possibly from Obama, who backed hemp when he was a state lawmaker in Illinois.
"Legalizing industrial hemp is a no-brainer," he said. "This is a sustainable crop. It's an environmentally minded, healthy industry. It's not a drug industry. I'm betting that this is the year."