Four Maine farmers will join dozens of others in Washington, D.C., on Thursday to hear oral arguments in a federal court case pitting organic farmers against the chemical giant Monsanto.

The U.S. Court of Appeals for the Federal Circuit is expected to rule within three months on the farmers’ appeal in a case concerning genetically modified seeds.

The case questions Monsanto’s legal basis for patents for genetically modified seeds and seeks blanket protection from patent-infringement lawsuits for farmers, should their crops be contaminated by unwanted pollination by Monsanto’s genetically altered plants.

By law, certified organic crops cannot contain genetically modified material.

While most of the plaintiffs in the case are organic farmers, some are conventional farmers who farm with seed that isn’t genetically modified and face the same risks of contamination.

Genetically modified seeds are protected by patents. Farmers who grow genetically modified crops must buy new seeds each year, and cannot use traditional seed-saving practices.

In February, U.S. District Judge Naomi Buchwald of the Southern District of New York dismissed the case brought by the national, nonprofit Organic Seed Growers and Trade Association, which is based in Washington, Maine. The lawsuit was originally filed in March 2011.

Traveling from Maine will be a potato seed farmer, Jim Gerritsen of Wood Prairie Farm in Bridgewater, board president of the Organic Seed Growers and Trade Association; a garlic seed farmer, Aimee Good of Good Dirt Garlic in Monticello; Margaret Liebman of South Paw Farm in Unity, who will represent Fedco Seeds of Waterville; and Holli Cederholm of Proud Peasant Farm in Washington, general manager of the Organic Seed Growers and Trade Association.

Cederholm said more than 30 farmers from across the United States and Canada who represent some of the 83 plaintiffs in the lawsuit will also be in the courtroom. They will be joined by other farmers with an interest in the case.

The nonprofit Public Patent Foundation is representing the farmers.

To coincide with the 10 a.m. start of the hearing, supporters of the farmers plan a rally in Washington’s Lafayette Square.

Staff Writer Avery Yale Kamila can be contacted at 791-6297 or at: akamila@pressherald.com

Twitter: AveryYaleKamila