How to grow rhubarb in your garden and where it's likely to thrive
Rhubarb is an ideal edible plant for many home gardeners, and another example of the few vegetable plants which are perennial, meaning that they regrow year after year after initial planting.
While rhubarb is considered a vegetable botanically, in the kitchen, it is used primarily as a fruit, many times in combination with another fruit such as strawberry or blueberry.
Strawberry-rhubarb pie, blueberry-rhubarb preserves and rhubarb crisp were common products of my grandmother's rhubarb planting.
Rhubarb (Rheum rhabarbarum) belongs to the Buckwheat family and is a cool-season hardy herbaceous perennial which grows from short thick rhizomes. A rhizome is a horizontal underground stem which stores nutrients and water.
Not only is rhubarb tangy and tasty, it is a good source of vitamins K and A, and is an excellent source of dietary fiber, which can help lower cholesterol.
Rhubarb was first cultivated in the Far East more than 2,000 years ago, primarily for medicinal purposes. In the 18th century, it was grown in Britain and America for culinary purposes.
Your climate will impact your ability to grow rhubarb, as it requires winter temperatures below 40 degrees Fahrenheit to break dormancy and stimulate spring growth and also needs summer temperatures averaging less than 75 degrees Fahrenheit for vigorous vegetative growth.
Planting rhubarb
Rhubarb is generally purchased as crowns or divisions, rather than propagated from seed, as it takes a very long time to grow from seed. Rhubarb crowns are sometimes available in early spring at garden centers or from seed catalogs and websites.
Common varieties that grow and produce well in the upper Midwest include MacDonald, crimson red, Victoria, Canada red, Cawood delight, Glaskin’s perpetual and valentine.
Rhubarb varieties vary in color and the number of seed stalks produced. Some varieties, such as valentine, are more likely to bolt than others and may not be the best choice for hot summer conditions experienced in Greater Columbus.
I have seen Chinese rhubarb (Rheum palmatum), also known as ornamental rhubarb, at local garden centers, but it is not edible.
Site requirements
Rhubarb will grow and flourish in most soils, but grows best in fertile, loamy, well-drained soil that has good organic matter content. Careful soil preparation will help rhubarb stay healthy and productive for many years. The planting area should be cleared of any weeds, especially tough, hard-to-control perennial weeds.
Choose a planting site for rhubarb which receives a minimum of six hours of direct sunlight, free from the shade of trees or buildings. Since rhubarb is a perennial, it should be planted to one side or at the end of a vegetable garden so as not to interfere with tillage and the production of annual vegetables.
The rhubarb plant grows in a large clump and has large distinctive foliage, and some gardeners find it suitable to include in a perennial flower bed.
Planting and care
Rhubarb crowns are best planted in early spring when the roots are still dormant, or the plants are just beginning to leaf out. Rhubarb can also be planted in the fall after dormancy has set in.
Individual crowns should be spaced 3 feet apart. Loosen the soil to a depth of 10 inches and add approximately 3 teaspoons of a complete fertilizer such as 10-10-10 per square foot of planting area.
Cover the crowns with no more than an inch or two of soil. Planting rhubarb crowns too deep will delay production. Press the soil firmly around the roots and water well. As soil and air temperatures begin to warm, new buds will push up through the soil.
Once the plants are up and growing, the addition of a 3-to-4-inch layer of clean straw, compost or similar mulching material will help control weeds and conserve soil moisture for plant growth and development.
Flower stalks should be removed as they appear, as they deplete nutrient reserves from the crowns which support vegetative growth. Rhubarb, like most vegetables, requires regular irrigation during dry weather. Keep the soil moist, but not soggy.
To maintain established rhubarb plants yearly, only fertilize with nitrogen (N). Apply N applications in the spring and again when active growth occurs. Side-dress 2 pounds of N and 2-3 inches of compost per 1,000 square feet of soil. Repeat after harvest as nutrients in the soil may be depleted. Do not work fertilizer into soil for established plants.
Harvest and storage
In order for the plant to become established, leafstalks should not be harvested the year in which they are planted, and only a few stalks should be harvested the second year. From the third year on, rhubarb can typically be fully harvested from late April through June in climates where it thrives.
Stop harvesting leafstalks when the plant begins to produce slender stalks, a sign that its nutrient reserves are low. Never harvest more than one-third to one-half of the plant’s stalks to preserve enough foliage to sustain the crown.
The stalks are most flavorful when young and tender, so harvest stalks soon after the leaf expands. Harvest by grasping each leafstalk near the base and pulling it slightly to one side.
Fresh rhubarb can be stored for two to four weeks at normal refrigerator temperatures and 95% to 100% relative humidity. Store in perforated polyethylene bags in the refrigerator crisper drawer for best results.
After the last harvest, the plants should be allowed to grow until killed by frost. After the tops are dead and the ground is frozen, the plants can be covered with 2-3 inches of straw mulch to reduce the risk of disease.
Remove mulch from the crown before growth starts in the spring, but leave the remaining mulch around the plants to control weeds.
Mike Hogan is Extension Educator, Agriculture and Natural Resources and associate professor with Ohio State University Extension.
hogan.1@osu.edu
This article originally appeared on The Columbus Dispatch: Rhubarb can thrive in these climates, here's how to grow it
