Maine Organic Farmers and Gardeners Association
Tips for Farmers and Gardeners

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Hard Frost and Oxalic Acid in Rhubarb Petioles

Rhubarb leaves contain oxalic acid, which can be toxic if eaten. When spring temperatures fall to the mid-20s or below, the plants may move oxalic acid into their petioles, making them unsafe to eat, too. So don’t eat rhubarb stalks after a hard frost, when leaves appear water-soaked and then wilt, eventually turning dry and black along the edges or where tissue was damaged; and don’t eat stalks that are limp or wilted. If you notice frost damage on rhubarb leaves, remove and compost the injured leaves and the stalks attached to them. The hard frost won’t kill your plants, and eventually you’ll see a new set of leaves and edible stalks. (“Question of the Week,” Weekly Market Bulletin, N.H. Dept. of Ag., April 29, 2009)

Planting More Soybean Seed Means Fewer Weeds
When five sites in North Carolina were planted with soybean seed at rates varying from 185,000 to 556,000 live seeds per hectare (about 2.5 acres), the sites with 556,000 live seeds per hectare had the greatest economic return for an organic treatment. (“Seeding Rate Effects on Weed Control and Yield for Organic Soybean (Glycine max) Production,” Weed Technology, Vol. 23, No. 4, October-December 2009;

Cuphea Good in Grain Rotations

Growing the oilseed plant called cuphea the year before growing wheat results in better wheat seedling survival and in grain that is 8 percent higher in protein, according to USDA Agricultural Research Service scientist Russ Gesch and colleagues, who conducted a four-year experiment rotating cuphea with corn, soy and wheat in Morris, Minnesota. Gesch recommends rotating soy with cuphea and then wheat or corn to increase the profitability of both wheat and corn. Cuphea, a new oilseed crop being developed for the northern corn belt, can be used for jet and other biofuels and for other industrial products, and it is a domestic alternative to palm kernel and coconut oils. Some 260 undomesticated species of cuphea are native to Central America, South America and North America. (“Cuphea Does Wonders for Wheat and Corn in Rotations,” by
Don Comis, USDA Agricultural Research Service News Service, Jan. 8, 2010;

MOF&G Cover Spring 2010