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2022 Midwest Vegetable Guide

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Rhubarb – Diseases 248 Midwest Veg Guide 2022 emerge. Use with another herbicide. Some varieties may be sensitive to Zidua. REI: 12-hour. HRAC 15. Rhubarb – Horticulture Major update by Ben Phillips, Liz Maynard – Oct 2020 Reviewed by Liz Maynard – Aug 2021 Crop Description Rhubarb is a plant of unknown European origin, but most commercial varieties are hybrids, Rheum x hybridum, that will not produce true from seed. Variety names have been lost, confused, and rebranded over the years. There are only a handful of varieties that can be sourced in the United States, and the varieties most grown commercially are Canada Red, MacDonald, Sutton, and Victoria – all red-stalked varieties. There are more productive varieties that produce green stalks, but red-stalked varieties are more popular at market and are more amenable to a process called "forcing". After two years of unharvested growth, plants can begin to be annually harvested in the field for 3 to 8 productive years. Alternatively, after three years of unharvested growth, plants can be dug in late fall or early winter and stored in dark indoor facilities where they are sprouted early for a lucrative late winter and early spring harvest, after which the roots are exhausted and discarded. Victoria is the most reliable forcing variety, and the most widely available. Planting and Spacing Use only young, healthy crowns having preferably 2 or 3 buds. Rows 5 to 6 feet apart. Set crowns 3 feet apart in shallow furrows so crowns will be 2 inches below surface. Break off flower stalks to maintain a strong root system year after year. Infertile soil, extreme heat or cold, drought, or long days that expose plants to too much light may cause bolting, and older plants bolt more. A productive planting can be maintained for 3 to 8 years. For forcing, crowns are placed in a dark room with about 1 square foot per crown on an open dirt floor, or in apple crates, and a few inches of soil is piled around each crown. Plants can be held dormant with temperatures below 40 degrees. Fertilizing pH: Maintain a soil pH of 6.2 to 6.8. New plantings: Before planting, apply 50 pounds N per acre, 0 to 150 pounds P 2 O 5 per acre, and 0 to 200 pounds K 2 O per acre based on soil test results and recommendations from your state. Apply an additional 25 pounds P 2 O 5 per acre directly in furrows when setting crowns. Sidedress with 50 pounds N per acre after growth starts in the spring. Established plantings: Each year before emergence, apply 50 pounds N per acre by broadcasting and incorporate by lightly tilling. After harvests conclude, apply 30 pounds N per acre. The total amount of N from fertilizer should be 80 pounds N per acre. No P 2 O 5 is necessary if adequate fertilization was achieved prior to planting. Every fourth year apply up to 120 pounds K 2 O per acre if a soil test recommends it. Harvesting Harvest no longer than 4 weeks, beginning with the third season of growth. Harvest for about 8 to 10 weeks after the third season. Do not remove more than two-thirds of the developed stalks from any plant at one time. Rhubarb is forced by wetting the soils around the crowns and maintaining a temperature between 50° and 65° F. The plants then produce many bright pink stalks for about one month and are usually picked twice a week. After experiencing a forcing process, crowns are generally too weak to produce well again. Rhubarb – Diseases Reviewed by Dan Egel – Sept 2021 Recommended Controls Leaf Spot of Rhubarb - Ascochyta Fungus Non-Pesticide Fertilize in the fall for growth in the spring. Improves rapid, strong plant growth and uniform establishment, and enhances competitiveness. Remove older yellowed leaves or leaves with lesions in the fall. Phytophthora Blight of Multiple Crops - Phytophthora Oomycete Non-Pesticide Use disease-free plants. Plant only on well-drained soil.

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