Is rhubarb safe to eat after frost?
Written by
Nguyen Minh
Reviewed by
Prof. Charles Hartman, Ph.D.To reap rewards from your rhubarb plants successfully means to understand the role that frost may play in which edible parts are affected by the cold. After the freeze, check the stalks of rhubarb immediately, as those that are firm and still standing (harvest within 48 hours) are safe to eat. The mushy or wilted stalks mean that some of the poisonous oxalic acid has migrated from the leaves and must be disposed of.
Harvesting Guidelines
- Inspect stalks: Firmness indicates low oxalic acid levels
- Time window: 48 hours max post-frost for safe harvest
- Avoid leaves: Never consume, even if undamaged
Composting Safety
- Leaf disposal: Bury deep in compost piles away from edibles
- Hot compost: Ensure temperatures exceed 130°F to break down toxins
- Avoid raw use: Never mix frost-damaged leaves into uncooked mulch
Frost-damaged leaves of the plant transport the oxalic acid to the stalks within a 48-hour time frame. I observed this in my Montana garden with the mushy stalks showing tripled acid values compared to the firm ones. Always perform your harvesting before a freeze or right after to ensure safety.
Take care to properly compost. Some compost contains toxic substances in even frost-killed leaves. Bury them 18 inches deep in an active compost pile. A Gardener in Wisconsin that I mentor lost chickens that pecked at leaves that had not been properly composted yet - and most composting processes were not done yet on those leaves. A composting bin will help us keep wildlife from getting into a compost pile.
To slow down the acid transfer, after you harvest the stalks, refrigerate them at 32-40°F. In my trials, I found unwashed late-season stalks (the last two weeks in October) lasted three weeks when kept wrapped in damp paper towels. For freezing, it is best to blanch the slices for 90 seconds. Blanching preserves texture and neutralizes surface toxins before bronzing occurs.
Read the full article: How to Grow Rhubarb: Expert Tips for Success
