Rhubarb Research Program

Rhubarb is a cool season, perennial plant that is very winter hardy and resistant to drought. Its crop is produced from crowns consisting of fleshy rhizomes and buds. Following a season of growth, the rhubarb crown becomes dormant and temperatures of -24C or below are required to break dormancy and to stimulate spring growth. Summer temperatures averaging less than -24C are required for vigorous vegetative growth. The first shoots to appear in the spring are edible petioles and leaves. These emerge sequentially as long as temperatures remain cool. As temperatures increase, top growth is suppressed, even appearing dormant in periods of extreme heat. With declining temperatures in later summer, foliage growth resumes.

Establishing a productive rhubarb crop takes a minimum of two years from planting. Crowns are planted in first year, fertilized, and left to establish. A selective cutting can be done in the second year, if growth shows promise. A good commercial yield is 15 tons (30,000 lbs.) per acre, while an exceptional yield is about 18 tons (36,000 lbs.) per acre. Once established, rhubarb plantings remain productive for 8 to 15 years.

Soil type

Rhubarb is tolerant of most soil types but grows well on fertile, well-drained soils with a pH of 5.5 to 7 with high organic matter. Lighter soils will produce an earlier crop but require more irrigation and fertilization. Fields to be planted should be plowed deeply and worked in the fall and/or spring. Established fields should be cultivated in the spring and following harvest.

Choose fields free of problem perennial weeds, or ensure effective control prior to planting. Weed control can be one of the highest labor costs if not effectively controlled, as there are no registered herbicides for use in rhubarb; therefore, herbicides are restricted during active growth of the crop.

Fertilizers

Rhubarb is a heavy feeder of fertilizer, especially nitrogen (N). A soil test is the most accurate guide to fertilizer requirements and is recommended on minimum bi-annual basis at minimum. The following recommendations are general guidelines, but growers can obtain custom recommendations from Knol Farms Ltd., upon request. Liming should be done if the pH is below 5.6. Manure may be applied in the fall or as early as possible in the spring. (Do not apply manure or fertilizer within 2 weeks of the lime application.)

In a planting year, apply the following:

• Prior to planting, broadcast and cultivate in 170 kg Nitrogen (N)/ha, with all Phosphorus (P) and Potassium(K) requirements (from soil test).
• Approximately one month after growth starts, side-dress with an additional 50 kg N/ha.

In subsequent years:

• Apply 100 kg N/ha with P and K requirements (from soil test) as a broadcast or sidedress just prior to bud-break
• Apply additional 100kg N/ha as a broadcast, approximately 1 week after harvest is complete
• Boron(B) may be applied if the soil level drops below 0.5 ppm at a rate of 2.5 to 5 lbs/ha or a foliar application of 1.25 lb/ha when plants are 6-8 inches tall.
• Nitrogen fertilizer applications can be split into 3 side-dressings; before growth starts in the spring, after growth starts and after harvest. Nitrogen rates may be reduced in the first two years with manure applications.
  * Note: If applying manure on farm an approved nutrient management plan should be in place on farm to balance fertility being applied through a combination of sources.

Planting

The crown pieces are planted 3 to 6 inches deep, and can be planted in a range of spacing depending on individual grower preference and harvest techniques. A recommended spacing is 2" to 3" apart, and rows about 4" to 6" apart. Another method of spacing would be in a 4" X 4" grid to allow for cross-cultivation, although we do not recommend this spacing due to the fact that it leads to higher incidence of weeds and a more difficult harvest.

Rhubarb intended for harvest using a harvest-aid trailer is planted 2\' apart in row 5\' apart. This spacing would require about 5,000 plants per acre.

Propagation

As much as possible, obtain planting stocks only from reputable nurseries. Plant crown divisions in March or April, or as soon as soil conditions allow. When rhubarb plantings are obtained from old fields, care should be taken to insure that crowns are free of disease.

Crowns may be dug in late fall and stored in a cool place for planting in spring, or dug in late winter or as early in spring as possible. Healthy, vigorous, three-year-old crowns can be divided, obtaining two or more buds per seed-piece, resulting in at least two crowns per plant for re-plant purposes. Five- or six-year-old crowns can yield 8 to 10 good quality pieces.

Irrigation

Maintain adequate soil moisture after the harvest season, to insure good re-growth. Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils needs more frequent water applications, but less water applied per application.

Growth enhancement

Rhubarb may start as early as mid-March, but often ends up being early June in the Maritime provinces. Do not harvest in the rain, fog, or heavy dew due to high incidence of rhubarb stalk brooming under these conditions. These will provide the reserves for the following year.

Yields of rhubarb depend on the variety, number of picking, the age and the condition of the field. True red varieties tend to yield less on average than non-red types. A yield of 20,000 to 25,000 lb/acre is most common at the first harvest. Green varieties tend to yield more. A well-maintained field may remain productive for 13 or more years.

Rhubarb is all harvested by hand; however, Knol Farms Ltd. is in the process of developing a more mechanized harvest system. At present Knol Farms Ltd. has two harvest aid trailers with trimming stations; for more information on these trailers and the development project, contact Teresa Pauley at Knol Farms office in Collingwood.

For processing, both ends of the petioles are trimmed so that no leaf tissue remains. Keeping with appropriate food safety procedures, fresh produce should always be handled in the utmost hygenic manner possible. Freshly harvested rhubarb should not be washed prior to shipment. All harvested rhubarb must be transported in clean pallet boxes, labelled with grower code, harvest date and a pallet number. Rhubarb must be transported to the processing plant within 24 hours of harvest due to the high risk of splitting in storage and therefore loss of product.

Storage

Store at 0 to 1^oC and 95 to 100% relative humidity. Fresh rhubarb stalks in good condition can be stored 2 to 4 weeks at 0^oC and high relative humidity, yet it is preferred by Knol Farms that all product to be processed is received within 24 hours of harvest. Rhubarb can be hydro-cooled or air-cooled, and the temperature of the stalks should reach approximately 0^oC within 1 day of harvest. The topped bunches or loose stalks should be packed in crates, and the crates should be stacked to allow ample air circulation; otherwise there is danger of heating and mold growth. Moisture loss in storage will be much less if the bunched or loose stalks are packed in crates lined with perforated polyethylene film.

Packaging

Rhubarb is packaged in both 16-lb. plastic pails as well as 4.4-lb. polyethylene bags, sold in cases of 6 by Knol Farms Ltd.

The RRP has research platforms in the following areas:

• canopy regulation
• crown management and propagule enhancement
• clonal diversity and adaptation
• bioactives and bioprocesses
• eco-physiology
• production physiology

Research partners

• Knol Farms (Teresa Pauley, Collingwood, NS)
• The Faculty of Agriculture (Kevin Sibley, associate professor, Dept. of Engineering, Truro, NS)
• Nova Scotia Department of Agriculture and Fisheries

Program director

Dr. Rajasekaran R. Lada
Professor, Plant Physiology
BSc (Horticulture)(TNAU, Coimbatore) – Horticulture
MSc (Agriculture)(TNAU, Coimbatore) - Horticulture-Olericulture (Abiotic Stress)
PhD (Adelaide, Australia) - Plant Physiology (Stress physiology and metabolism)

Email: raj.lada@dal.ca

Other collaborators

• Azure Adams, scientific officer
• Usha P. Rayirath, graduate research assistant
• Samantha Feltmate, graduate research assistant
• Andrea Munroe, NSERC research assistant

Portion size: 100 grams

Vitamin content

• Ascorbic Acid 8 mg
• Thiamin 0.02 mg
• Riboflavin 0.03 mg
• Niacin 0.3 mg
• Pantothenic acid 0.09 mg
• Vitamin B6 0.02 mg
• Folate 7 mg
• Vitamin B12 102 ug

Mineral content

• Calcium86 mg
• Copper 0.02 mg
• Iron 0.22 mg
• Magnesium 12 mg
• Manganese 0.2 mg
• Phosphorus 14 mg
• Potassium 288 mg
• Sodium 4 mg
• Selenium 1.1 mg
• Zinc 0.1 mg

Rhubarb has a long history in traditional Chinese medicine for treatinga variety of illnesses and diseases.

Bacterial infections

Rhubarb contains anti-bacterial compounds that control Staphylococcus aureus infections. Root decoctions of rhubarb were traditionally applied to wounds and pustules for arresting bacterial infection.

Constipation

Rheum palmatum contains a laxative compound that stimulates strong muscular contractions of teh bowel wall and hastens bowel movements.

Urinary tract lesions

Experimental data suggests that Chinese rhubarb is effective in preventing or at least partially reversing various kinds of kidney lesions.

Cholesterol

Chinese rhubarb extract was found to lower total and low-density lipoprotein cholesterol levels and increase high-density lipoprotein cholesterol and albumin levels in patients with chronic renal failure, when compared with untreated patients.

Courtesy of Mrs. Yvonne Burke, Newfoundland

Rhubarb Lemonade

Ingredients

• rhubarb - 8 cups
• sugar - 3 cups
• water - 3 cups
• lemon zest - 3 tbsp.
  

Procedure

Cook all this together. Put through a sieve and when it is cooled add 1 1/2 cups of fresh-squeezed lemon juice. To serve, use 1 part concentrate to 3 parts water.

Rhubarb Jelly

Ingredients

• rhubarb - 4.5 cups
• Certo - 2 pouches
• sugar
  

Procedure

Put rhubarb in a blender and let drain in a jelly bag overnight. To 3 1/2 cups juice, add 7 cups of sugar. Bring to a boil for 1 minute. Add Certo. Bring to a full boil for 1 minute. Remove from heat and remove foam. Pour into sterilized jars. Boil in boiling water for 10 minutes.

Rhubarb Cake

Ingredients

• mini marshmallows
• white cake mix
• rhubarb - 3 cups
• sugar - 1 cup
• strawberry Jell-O - 1 pkg
• water - 1 cup
  

Procedure

Put a layer of mini marshmallows on bottom of a 9 x 11 bake pan. Mix cake mix as per instructions on box. Pour over marshmallows. Cook Rhubarb, and add 1 cup of water and bring to a boil. Add Jell-O and spoon on top of cake mix. Bake 350 degrees for 30 minutes. Enjoy!

Rhubarb Relish

Ingredients

• rhubarb - 1 quart
• onions - 1 quart
• vinegar (malt preferred) - 2 cups
• brown sugar - 4 cups
• cinnamon - 1 tsp
• ground allspice - 1/2 tsp
• ground cloves - 1/2 tsp
• pepper - 1/4 tsp
  

Procedure

Wash and cut rhubarb into 1-inch pieces. Peel and chop onions quite finely. Combine all ingredients and boil gently until fairly thick. Pour into hot sterilized jars and seal.

Rhubarb Carrot Marmalade

Ingredients

• shredded carrots - 4 cups
• diced rhubarb, ¼-inch thick pieces - 4 cups
• 2 oranges, cut into very thin slices and cut in half
• 2 lemons, cut into very thin slices and cut in half
• sugar - 6 cups
• water - 1 1/2 cups
  

Procedure

Peel carrots, shred. Wash & dry rhubarb, oranges and lemons and cut up. Combine all ingredients and bring to a boil, stirring to prevent scorching. Boil for 1 hour. Pour into hot sterilized jars and seal.

Rhubarb Raspberry Sauce

Ingredients

• sliced rhubarb -1/2 inch slices fresh / frozen - 2 1/2 cups
• sugar - 1/2 cup
• water - 3/4 cup
• grated rind and juice of 1 lemon
• cinnamon - 1/4 tsp
• fresh raspberries - 2 cups OR frozen unsweetened raspberries - 1 cup
  

Procedure

In a saucepan, combine rhubarb, water, sugar & lemon rind; bringing to a boil over medium heat. Reduce heat; stir in lemon juice, cinnamon and raspberries. Let cool. Serve warm or cool over vanilla ice cream. Makes about 3 cups of sauce.

Strawberry Rhubarb Pound Cake

Ingredients

• fresh rhubarb -1-inch slices - 1 lbs.
• halved strawberries - 2 cups
• sugar - 1/3 cup
• frozen pound cake, thawed cut into 10 slices
• Cool Whip, thawed - 1 1/3 cups
  

Procedure

Toss rhubarb and strawberries with sugar in a large saucepan. Stir in 2 Tbsp. water. Cover and cook on medium heat 5 min. or until rhubarb is desired tenderness, stirring occasionally. Remove from heat; cool slightly. Refrigerate at least 2 hours or until ready to use. Place 1 slice of pound cake on each dessert plate when ready to serve. Top each cake slice with about 1/4 cup of the rhubarb mixture and about 2 tbsp. of whipped topping. Serve immediately.

Rhubarb Catsup

Ingredients

• rhubarb - 12 cups
• brown sugar - 5 cups
• chopped onions - 3 cups
• white vinegar - 1 1/4 cups
• salt - 1 tsp
• cinnamon - 1 tsp
• ground cloves - 1 tsp
• pepper - 1/2 tsp
  

Procedure

Cut rhubarb into small pieces. Wash and drain. Add sugar to rhubarb and let stand for 2 hours. Then add the chopped onions, vinegar and seasonings. Boil for 30 minutes or until thick. Stir occasionally to keep from sticking.

Nurseries

• Cornhill Nursery, New Brunswick
• Gurney's Seed and Nursery (online shop)
• Blake Nursery
• Boughen Nurseries
• Briar Patch Nursery
• Hortico Nurseries Inc.
• Nourse Farms Inc.
• Indiana Berry and Plant Co.
  
• Strawberry Tyme Farms Inc.

Institutions/organizations

• Agriculture, Fisheries and Aquaculture, Prince Edward Island, Canada
• University of Illinois Extension, United States
• Horticulture Nova Scotia, Canada