Rhubarb and Asparagus

Recommended rhubarb varieties for North Dakota are Valentine, Ruby, MacDonald, Canadian Red and Sunrise. Unnamed heirlooms from farmsteads or family gardens can also be prolific producers.

Deep and fertile loamy soil high in organic matter is best suited for growing rhubarb. Composted manure added in the fall will benefit most rhubarb beds. Yields will be increased with clean cultivation and added organic matter. Rhubarb is often planted to one side of the garden, where it will not be disturbed if the main garden is plowed or rototilled in the fall. The end of an asparagus row is a suitable location, as rhubarb also requires full sun to grow successfully. If more than one row is planted, rows should be spaced 5 feet apart, with plants spaced 3 to 4 feet apart within the row. Plant crowns about 4 inches deep.

Rhubarb is typically propagated by division of the crowns formed during previous seasons. Divide crowns in late fall or early spring taking care to leave as much root as possible with each eye or bud. Plants from such crown divisions are preferred to plants raised from seed. Plants grown from seed seldom equal the production or quality of the named rhubarb varieties, and growing them from seed is not recommended.

Divide and reset plants about every fourth year to keep the bed in vigorous condition. Use a sharp spade or shovel to divide the crown, leaving three to four buds undisturbed in the old location. Portions removed may be used to enlarge the bed.

Renewal work should be done in the fall or early spring. Plants not divided in this manner become large and the stalks become more numerous than what is desirable. When seed stalks appear, remove them promptly as they reduce yield and affect the vitality of the plant.

Select firm, crisp stalks at about 8-15 inches long. Remove stalks from the base of the plant by firmly pulling and twisting. Do not overharvest. By July, rhubarb is finished producing for the season.

There are not many cases of rhubarb disease or pests in North Dakota. Occasionally leaf spot diseases, Ascochyta rhei and Ramularia rhei, are detected. To treat these diseases, remove infected stalks and remove and destroy all leaves after the first hard frost. Pesticide use is often not necessary.

Some varieties are a hybrid of the male and female plant. Recommended varieties for North Dakota are Millenium, Jersey Giant, Jersey Knight, Jersey Supreme and Purple Passion. Most recommended varieties are male, as the female plants will put more energy into flower production.

To grow asparagus successfully, choose a site with full sun and well-draining soil. Avoid sites that may become waterlogged during spring rains. Site preparation should be started a year or more in advance of planting. This preparation aids in complete control of hard-to-kill perennial weeds, such as quackgrass and Canada thistle.

In the fall before planting, incorporate organic matter, such as compost, into the soil; this will enhance growth and establishment. If compost is not available, a cover crop can be planted and plowed down the preceding year. The goal is to add as much organic matter as possible. With careful selection, an asparagus bed can last 15 or more years.

Asparagus may be started from seed. However, if only a few plants are needed for the home garden, purchasing the crowns from a seed company or nursery usually is best.

Plant year-old asparagus crowns in early May by digging a trench 10 to 12 inches deep in sandy soils or 6 to 8 inches deep in heavy clay soils. Keep the soil from the trench nearby to cover the plant as it grows. If planting rows, space them 4 to 5 feet apart.

When planting, lay crowns from “head to toe” along the trench and cover with 2 to 3 inches of soil. Water immediately to prevent crowns from drying. Once the ferns have emerged and grown, add remaining soil.

Asparagus should not be harvested before its third season of growth, no earlier. Shoots are best when cut at 6-10 inches high. To harvest, push a knife into the soil close to the shoot and cut it just below the soil surface or simply snap the shoot off. Do not harvest beyond June, as asparagus needs the time to store energy for the next season. For best quality, harvest in the morning.

Because harvest may begin when frost is still possible, do not allow emerged shoots to become frosted. Frost damage to shoots will inhibit the crowns from yielding at the optimum level.

Asparagus responds to annual applications of fertilizer. Composted manure or compost can be applied in the fall. One annual application of commercial fertilizer can be broadcasted over the row at the rate of 1 to 1.5 pounds per 100 square feet. A soil test is recommended for exact fertilizer recommendations. Fertilizer may be applied in late fall, very early in the spring or after the harvesting season has ended in late June.

A good indicator for a high yield in the following season is vigorous top growth. Hand weeding during the first year is a necessity as herbicide use may damage plants. Herbicide use should be minimal. Use only those labeled for asparagus.

Allow the tops to stand through the winter to catch and hold snow. This may help prevent deep freezing and sudden changes in soil temperature. Also, the added moisture provided by melting snow is important to the crop of shoots produced in the spring. Before growth starts in the spring, remove the dead tops.

Few diseases and pests impact asparagus production in North Dakota. Asparagus beetle can be an issue to home gardeners leading to hook-shaped ends. Treatment often includes hand removal of adult beetles and larvae, removal of plant residue and pesticide treatment for heavy infestations.

This publication was originally authored by Ronald Smith, former NDSU Extension Horticulturist.