Rhubarb and Asparagus After a Frost-Can I Eat It?

Rhubarb and Asparagus After a Frost – Can I Eat It?

With the very chilly temperatures experienced in Northeast and Northern Wisconsin for the past several weeks and most recently, the overnight temperatures dropping to or near freezing, you may have questions about the safety of eating rhubarb and asparagus. Please see the information below prepared by the University of Illinois Extension.

Growing rhubarb is fairly easy as long as Mother Nature keeps temperatures above freezing once the leaves have emerged.  Rhubarb should not be harvested when the leaves are wilted and limp after a hard freeze.The part that we consume is the petiole or the leaf stalk.  Rhubarb leaves should never be eaten since they contain a toxic substance called oxalic acid.  Under normal harvest the leafstalk is cut at the base and the leaf blades are trimmed off.  After a hard frost oxalic acid may move from the leaves into the leafstalk.  When consumed the oxalic acid can crystallize in the kidneys and cause permanent damage to the organs.

In addition to the potential toxicity, the rhubarb leaf stalks will be of poor texture and flavor.

All rhubarb leaf stalks/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 insure the plant will return next season.

Asparagus harvest also is affected by cold temperatures – but it does not have the toxicity issues like rhubarb.  You can expect to see frost damage to the exposed spear tips.  These are edible but they are off flavor and will have a softer texture.

Asparagus will start to re-grow as the temperatures warm up.  A mature planting can be harvested until spears become thin and spindly.  This thinning is a signal telling you to stop harvesting for the year and allow the ferns to grow.

Source: Martha A. Smith, Extension Educator, Horticulture, smithma@illinois.edu