my rhubarb got frost bite is it safe to eat
Cottonwood County Minnesota rhubarb
Like many plants, rhubarb contains oxalic acid in its leaves. Oxalic acid can be poisonous in large amounts. Freezing, which doesn't occur unless the temp drops to the mid 20s, causes the acid to move from the leaves into the stalks. If the damage is severe - the stalks are mushy or floppy and the leaves look black - remove those pieces and wait for the replacement stalks to grow. Not only would they have an excess of oxalic acid but they would taste awful. It can take a couple of days for the damage to show.