After our region’s recent spring cold snap, there have been many questions about rhubarb plants that were exposed to freezing temperatures. Many homeowners’ rhubarb was up and growing, and there’s a rumor that circulates every spring about the dangers of eating rhubarb after frost. Is this true?
Rhubarb leaves contain oxalic acid, which can be a toxic substance if consumed in large enough quantities. That’s why we do not eat the leaves of rhubarb. When rhubarb plants are exposed to freezing temperature, some of the oxalic acid can travel from the leaves down into the stalks, but there are obvious clues when this happens.
So how do you know if oxalic acid has traveled downward, and how do you know if the stalks are ok to harvest and eat?
Many universities have studied this, issued recommendations and agree on the following:
- If stalks become limp after frost, don’t harvest them. Instead pull and discard.
- If leaves show damage from frost, such as blackened edges, watersoaked frost injury, etc., pull and discard the stalks, even if the stalk itself is firm.
- If stalks and leaves appear normal after a frost, the rhubarb is safe to eat.
- If stalks and/or leaves are damaged, resulting in needing to pull the damaged stalks, all future regrowth is safe to eat.
- If in doubt or you’re hesitant, just don’t use it.
- Any time rhubarb is harvested, the stalks are better gently pulled, rather than cut.
Rhubarb usually begins to grow in late April in the Upper Midwest. And because our region’s final frost is often mid-May, rhubarb plants have been getting frosted since pioneer days. And unless it’s obviously damaged, rhubarb stalks have been making pies and sauce each spring, even after the common spring frosts.