When to Harvest Rhubarb

The first three years

Restraint in the early years pays off for a decade or more. The sources agree on the first year: harvest nothing. They differ on the second. Arkansas allows one or two weeks of picking, Ohio State says a few stalks, and Oregon State suggests just 3 or 4 stalks per plant. Utah State takes the cautious line and recommends no harvest at all for two full years, then 3 to 4 weeks in year three. Wisconsin says to wait until the second or third year. Weak plants are better off with Utah State’s approach.

From the third year on (Utah State says the fourth), you can take a full season. Arkansas gives 8 to 10 weeks, Oregon State about 8, and Utah State 6 to 10 weeks or until the plant starts losing vigor.

Signs a stalk is ready

Look for stalks that are firm, crisp and roughly 8 to 15 inches long; Wisconsin gives 8 to 15 inches and Utah State 10 to 15. Ohio State notes that flavor is best when stalks are fairly young, so pick soon after the leaf has unfolded rather than waiting for the largest stalks. Arkansas says color, flavor and tenderness peak in early spring. Texas A&M’s Aggie Horticulture adds that younger, darker pink, slimmer stalks are sweeter and more tender than long, thick green ones.

Color is a poor guide: it depends on variety and night temperatures, and Wisconsin notes that red stalks are not necessarily sweeter.

The harvest season

The season opens as soon as stalks reach usable size in spring. In Ohio that means from late April through June, with the last picking in early July. Oregon State describes a main picking in May and another in early to mid July. Ohio State and Oregon State both say to let the plant grow unpicked after that, and Oregon State sets late July as the cutoff, because harvesting in late summer delays the next spring’s crop and can cut yield and vigor. As the leaves decline in August and September, the roots store the food that fuels next spring’s growth. Wisconsin adds that young plants should be picked only in spring, while vigorous established plants can take light picking through summer.

In central Texas, where rhubarb is grown as a winter annual from seed, harvest runs from about March through May (Texas A&M AgriLife, Travis County).

Arkansas advises against fall harvest unless you plan to remove the plants the following season.

How much to take

Never strip a plant. Utah State says to leave a third of the stalks at all times, Ohio State to take no more than a third to a half, and Wisconsin no more than a third of the leaves in a year. Oregon State’s rule of thumb is to keep about half a dozen stalks on the plant. The leaves left behind are what refill the crown.

The plant will tell you when to stop. When new stalks come up slender, its reserves are low, and Ohio State says to end the harvest there even if the calendar says otherwise. A healthy plant yields roughly 4 to 12 pounds of stalks a year, depending on age, variety and growing conditions (Utah State).

How to pick

Take hold of the stalk low down, near the crown, and pull it up and to one side with a slight twist. It should snap cleanly. Oregon State stresses doing this gently enough not to damage the bud at the base, since each bud produces several stalks. Utah State says never to cut stalks, because the stub can become an entry point for disease; Ohio State calls cutting debatable for the same reason, while the Travis County office in Texas says cutting is fine. Pulling is the safer habit.

Trim off the leaf blade right away and leave it in the garden or compost pile. In hot weather, the Travis County office suggests picking in the morning because the leaves wilt quickly in the heat.

Leaves, frost and safety

Only the stalks are eaten. The leaf blades contain high levels of oxalic acid, which Utah State says can cause serious illness and kidney failure, and Oregon State notes they are toxic to animals as well as people. The stalks contain very little. Composting the leaves is safe; the acid breaks down in the pile.

A hard freeze after the leaves are up complicates things. Ohio State says stalks that stay firm and upright can still be used, but any that turn soft or mushy should be thrown out, because severe cold can move oxalic acid from the leaves into the stalks. Oregon State gives the same warning. Arkansas and Wisconsin go further and advise not harvesting stalks after a severe or hard late freeze at all. When in doubt, compost the damaged stalks and wait for new ones.

Storing the harvest

Cut off the leaves, then refrigerate the stalks in plastic bags. Utah State and Ohio State give 2 to 4 weeks, Aggie Horticulture 2 to 3 weeks, and Wisconsin up to two weeks for unwashed stalks. To freeze, Utah State recommends blanching cut stalks in boiling water for 1 minute, chilling them in ice water and packing them tightly, with or without sugar. Wisconsin says frozen rhubarb keeps about 6 months.