How to Grow Rhubarb: Diseases, Harvesting and Recipes
Discover the Joy of Growing Rhubarb for Summertime Recipes
By Teresa Flora – In much of North America, spring is welcomed with the tart and tangy taste of fresh rhubarb. Rhubarb is one of the easiest and most rewarding perennials. There are just a few rhubarb diseases and pests to consider. It is technically a vegetable; however, it is used as a versatile fruit. For this reason, early settlers called it “pie plant.”
The earliest records of this easy-to-grow perennial date from about 2700 B.C. The Chinese used it for medicinal purposes then (and still do). It was much later that rhubarb was introduced into Europe. Records show cultivation at Padua, Italy around 1608. Twenty-five years later, seeds were obtained for planting in England. It was the 1770s before it was definitely recorded as a food there, used for making tarts and pies. A gardener in Maine got rhubarb from Europe about 1800 and introduced it to market gardeners in Massachusetts. In 1822, it was generally grown and marketed in Massachusetts. It was listed in an American seed catalog in 1828. As the pioneers moved westward, rhubarb went with them. “Pie plant” was easy to move and quicker to establish in a new location than fruit trees.
McDonald, Valentine and Victoria are popular varieties today. However, a friend or relative who has rhubarb will probably be glad to divide theirs with you. Hills should be divided every three to four years. Slender stalks show a need for division or feeding.
Rhubarb can be divided in the spring or fall. Use the shovel to cut the old root into pieces with two or three buds at the top. Plants that are divided in the fall should be heavily mulched for winter protection. Plant in well-drained, fertile soil. Set roots in holes six inches deep and two feet apart, with crowns just below the surface. If you live in an area with hot, dry summers such as we have here in central Kansas, you can plant rhubarb where it will get partial shade. You must live in an area where the ground freezes to a depth of several inches in the winter in order to grow rhubarb.
Rhubarb should be harvested only lightly the second and third years, until the roots are well established. An established patch will often last 25 years or more. Rhubarb stalks should be pulled instead of cut. Cutting encourages rhubarb diseases and insect infestations. Use only the stalk as food. Rhubarb leaves contain oxalic acid, which is poisonous. Never use them for food. (Ed. note: Don’t feed the leaves to animals, either.)
Top dress with a heavy application of organic matter in either early spring or late fall. Organic matter applied over the hills during early spring hastens growth by forcing the plant. Remove seed stalks as soon as they appear to prevent them from draining the plant. You can expect a yield of three to five pounds per plant. If established plants receive plenty of moisture, they can be harvested until late summer.
If you are adventurous and have no use for the divisions you make in the fall, you can keep them for forcing indoors. After digging the roots in the fall, put them in a box filled with peat moss or sawdust. Store in a dark place in the cellar. In January, soak the peat moss or sawdust with water. Keep the box cool and dark. In a few days, the rhubarb will send out little stalks. They look a little like asparagus shoots, because they have no leaves. They taste great! Thaw some frozen strawberries, mix in the rhubarb shoots, and make an easy pie recipe for strawberry-rhubarb pie. Roots that are forced indoors will not produce well if planted outdoors in the spring.
Rhubarb Diseases and Rhubarb Pests
When growing rhubarb, diseases and insects shouldn’t be a major concern, but there are a few that should be mentioned. Crown rot is a rhubarb disease for which there is no cure. The plant begins to yellow and then collapses. Dig and burn the roots, being careful not to scatter infected soil. Do not plant rhubarb back into the same location.
Anthracnose attacks all parts of the plant above the ground. Examine stalks for watery spots which enlarge as the rhubarb disease progresses, Leaves will wilt and die. As soon as you spot this rhubarb disease, apply a fixed copper or sulfur-based fungicide every seven to 10 days. Do not harvest for three to four weeks after application.
Leaf spot has symptoms similar to anthracnose. Spots first appear water-soaked and then grow in size and take on a brownish or purplish-gray color. It cannot be cured. Plants affected by leaf spot should be removed and destroyed.
Plants with verticillium wilt are often affected early in rhubarb season with yellow leaves. The beginning of this rhubarb disease is often mistaken for a nutrient deficiency. Then as the rhubarb disease progresses, the yellowed leaves wilt and the edges and veins of the leaves die. Remove and destroy plants.
A rhubarb pest known as curculio is a 1/2 to 3/4- inch long yellowish beetle with a sucking snout. They bore holes and lay eggs in the stalk and cause black spots to appear. Hand pick them off as sprays do not seem to control the. Destroying dockweed near rhubarb may be helpful in controlling curculios.
Leaves of plants affected by spider mites become yellow and dry, or have pale yellow spots caused by mites sucking chlorophyll out of the leaves. They also inject toxins into the leaves, which discolor and distort them. When you suspect this problem, look at the undersides of the leaves. If you see what appears to be a tiny red, brown, or black speck of dirt, touch it. If it moves, it’s most likely a mite. Spray plants with a forceful spray of water three times, every other day, to knock mites off. If that doesn’t do the job, spray the undersides of leaves with insecticidal soap at least three times at five- to seven-day intervals.
Plants infected with whitefly appear to have dandruff falling off when shook. The plants will be weak. The result of whitefly damage is yellow leaves that eventually die. Honeydew from whiteflies drops on stalks and encourages fungal growth. As a result, stalks are undersized and poorly colored. Spray with insecticidal soap every two or three days for two weeks. As a last resort, spray with pyrethrum two times, three or four days apart.
These pests are uncommon in rhubarb and unlikely to cause you trouble. Soon you will be having an abundance of rhubarb. Any surplus that you are unable to use now may be frozen or canned for future use. There are several successful methods of freezing. Food preservation of rhubarb via freezing begins by washing the stems and cut in one-inch pieces. Freeze the pieces on baking sheets or shallow pans. After the pieces are frozen, they should be packed into airtight containers or plastic bags. The advantage of this method is that you can remove the exact amount that the recipe calls for. Rhubarb may also be sugar packed by mixing one cup of sugar with four or five cups of rhubarb. Let stand until sugar is dissolved. Pack into containers leaving 1/2-inch headspace. Freeze. Another method is to syrup pack. Place rhubarb into containers. Cover with cold, 40-50 percent syrup. Leave 1/2-inch headspace. To make 40 percent syrup, dissolve 3 cups sugar in 4 cups water. To make 50 percent syrup, use 4 cups sugar to 4 cups water.
Rhubarb can also be canned. Wash and cut into 1/2 to 1-inch pieces. Add 1/2 to 1 cup sugar for each quart. Let stand until juicy — about 3 or 4 hours. Bring to a boil slowly in a covered pan. Pack into clean jars. Adjust lids. Process them (pints or quarts) in boil- ing water bath for 10 minutes. Rhubarb can be used in a variety of ways from refreshing drinks to marmalade to Jell-O to pies.
4 cups diced rhubarb
1 cup granulated sugar
1 box strawberry Jell-O
1 white cake mix (homemade, preferably)
1 cup water
1 stick butter, melted
Preheat oven to 350°F.
Grease 9 x 13 cake pan. Place rhubarb in pan. Sprinkle with sugar and Jell-O. Sprinkle cake mix evenly over top. Pour water and melted butter over cake mix. Bake for approximately 1 hour. Serve with ice cream or whipped cream.
In a 4 qt. pot, fill half full of rhubarb and fill up with water. Bring to a boil. Let stand 1⁄2 hour, drain. This can be canned. To make drink:
1 small can frozen lemonade
1 small can frozen orange juice
2 qts. rhubarb juice
3-1/2 qts. water
1 pkg. raspberry Kool-Aid
2 cups sugar
Mix all together. Add ice cubes.
Rhubarb Refrigerator Dessert
1 cup sugar
3 tablespoons cornstarch 1/2 cup water
4 cups chopped rhubarb
2 cups graham cracker crumbs 1/2 cup butter (or margarine)
1 cup whipped cream
1-1/2 cup miniature marshmallows 1/4 cup sugar
1 pkg. vanilla pudding
Filling: Stir sugar and cornstarch together. Stir in water. Add rhubarb. Boil until thick. Set aside to cool.
Crust: Combine graham cracker crumbs and melted butter. Reserve 1⁄4 cup for garnish on top. Press remainder of crumbs against sides and bottom of 9-inch square baking dish.
Topping: Spread rhubarb mixture over crust. Top with sweetened whipped cream combined with marshmallows. Prepare pudding according to package directions. Spread over top. Sprinkle with reserved graham cracker crumbs and refrigerate.
Originally published in Countryside March / April 2013 and regularly vetted for accuracy.