The Agriculture Department rule change on its own did not help. “They understood that hemp was removed from the federal Controlled Substances Act but because of the paperwork that was involved, a lot of them were just like, yeah, it’s just not worth it,” she said.

Rob Nichols, the president of the American Bankers Association, a trade group, said his members had been pushing for the change for some time.

Last month, the association surveyed 1,800 agriculture-focused banks in the country and found that almost half had gotten questions from their farmer-customers about whether they would still do business with them if they started growing hemp.

“We appreciate the steps regulators have taken today to clarify regulatory expectations for banks, and we look forward to working with them as they develop additional guidance,” Mr. Nichols said.

While the change will help businesses making clothes and other hemp products, it does not affect the legal marijuana businesses dealing with the same problems. The federal government still considers marijuana to be illegal, and even local banks have been too worried about getting in trouble to deal with them.

But banks large and small have come together to support a bill in Congress, the SAFE Banking Act, that would legalize marijuana banking by stipulating that the proceeds of a state-sanctioned marijuana business would not be considered illegal under federal anti-money-laundering laws.

The House of Representatives passed a version of the bill, and the banking industry is pushing the Senate to take it up. If it were to become law, it would let banks dive into a lucrative new industry that has been plagued by security concerns and is desperate for even the most basic services, like checking accounts and credit card processing.