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U of I Extension Specialist Warns Against Eating Frost-Damaged Rhubarb

This article was originally published on April 14, 2007 and expired on May 6, 2007. It is provided here for archival purposes and may contain dated information.

"Rhubarb should not be harvested when the leaves are wilted and limp after a hard freeze," warns Elizabeth Wahle, University of Illinois Extension horticulture specialist. "Not only do the leafstalks acquire a poor flavor and texture, but the leaves and eventually the stem may become toxic."

Wahle says rhubarb leaves should never be eaten, and petioles (the part you eat) should be harvested ONLY from plants that have suffered no frost damage. Rhubarb leaves contain oxalic acid, a toxic substance that may move into the petioles after frost damage. When consumed, the oxalic acid can crystallize in the kidneys and cause permanent damage to the organs.

All petioles that have been exposed to freezing temperatures should be removed and discarded. The re-growth is safe to eat. As normal harvest begins, always leave at least one-third of the petioles un-harvested to sustain the plant.

Asparagus harvest has been interrupted by the recent cold weather as well. Unlike rhubarb, asparagus does not become toxic after exposure to freezing temperatures. In fact, rhubarb is one of the few crops that have this characteristic.

"As asparagus starts to re-grow, expect to see some frost damage on the tips of the first spears," says Wahle. "The spears are still edible but most likely will have a softer texture which results in an even shorter shelf life."

Harvest can continue until spears become thinner, appearing somewhat spindly. This thinning is a signal from the root system to stop harvesting and allow the ferns to grow.

Source: Elizabeth Wahle, Extension Educator, Horticulture, wahle@illinois.edu

Pull date: May 6, 2007

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