Getting to know rhubarb
Rhubarb is also called "pie-plant" because the chopped stalks are often cooked, sweetened, and used as a pie filling, often with strawberries. It can also be used in breads and cakes, sweetened and used as a sauce, or cooked with sugar, strained and drunk as a refreshing juice. Few people can eat much rhubarb as a raw vegetable; while juicy and crisp, it is very sour.
Different varieties have varying levels of sourness and fibrousness, and they also vary in color from almost pure green to almost pure red. The flavor does not correlate with the color of rhubarb. Redder varieties are particularly desirable for pies because the color of the fill is more attractive than the grayish color of cooked green varieties. However greener varieties are more vigorous and have longer stalks than red varieties.
Only the long, thick leaf petioles, the "stalks," are edible. Rhubarb leaves are toxic and must never be eaten. The stalks do contain high levels of oxalic acid, (also found in spinach) which can tie up calcium and make it unavailable in the body. However eating an occasional dish containing rhubarb does not pose a serious nutritional threat. People with gout, kidney disorders, and rheumatoid arthritis may want to avoid such foods and consult their physician.
Rhubarb plants are very large, and a single plant usually provides enough for any family. Each plant should be allowed a three-foot by three-foot area in the garden that will receive sun all day. Rhubarb is hardy in USDA Zone 4 however it seems to survive in Zone 3 with a little extra care. Rhubarb plants are considered heavy feeder. Producing its large stalks and leaves requires that the plant take in large amounts of nutrients and water from the soil. Make it an annual practice to supplement the soil with either a balanced commercial fertilizer or rich compost and manure, or both. Proper watering will enhance good production. Soak the soil thoroughly when watering, to a depth of at least one inch each week during the growing season, especially if there is a severe drought.
To pick rhubarb, hold the stalk firmly, pull, and twist. Using a knife to cut the stalks from the plant is not recommended. The knife can carry diseases from plant to plant, and the remnant of the stalk serves as a point of entry for other pests. Immediately upon harvesting, use a knife to trim the leaves from the stalks and discard. Leaving them on can speed wilting of the stalks.
You can harvest rhubarb until the end of June. However it is best if you do not harvest more than half the plant. Than allow the plant to keep all of it leaves and stalks to build up its reserves of energy for the next season's crop. A common myth is that the entire plant becomes toxic later in the summer. This is not true: If a few stalks are pulled on one occasion later in the summer to prepare a special dish, plant health and vigor will not be affected although the stalks may be tougher than spring-harvested rhubarb. Also when seed stalks emerge from the plant, cut it off as soon as you notice it. If a plant is allowed to flower and set seed, it will use up food energy that should go back to the roots as reserves for winter and next year's crop.
Rhubarb plants are often neglected once the harvest season is over, but it is a good practice to continue watering and weeding all summer long. The plants can live 15 or more years with good care.
Kyle Schulz is a Wadena County Master Gardener from Sebeka, and the regular gardening columnist for the Wadena Pioneer Journal.