Rhubarb variety names are often confusing. Different names are often
assigned to the same variety in different regions or countries as people move planting material
from one location to another. An excellent source of information on rhubarb names is: A
Bibliography of Rhubarb and Rheum Species, Bibliographies of Literature of Agriculture, Number 62, 1988,
U.S. Department of Agriculture. A good on-line source of information on rhubarb (Rheum) species
as well as a wealth of other information and links on rhubarb is The Rhubarb Compendium.
Hothouse rhubarb is produced in Washington and Michigan with the total
U.S. production of hothouse production being about 175 acres. Total field and hothouse
production in the U.S. is about 1200 acres. This is produced mostly in the states of Oregon, Washington
Rhubarb varieties are classified as red or green. Green types are again
differentiated as green and speckled (pink).
Red stalk types:
Crimson (may also be called Crimson Cherry, Crimson Red, or Crimson
Wine). This is reportedly the only variety of consequence in Oregon.
It produces brightly colored red stalks with the unique characteristic of
being red throughout under normal temperature and moisture conditions of the Pacific Northwest.
Other vigorous red varieties are Valentine and Cherry Red
(Cherry, Early Cherry?) which is reportedly grown in California, producing
long, thick, deep-red stalks.
Speckled types (pink):
Victoria produces large stalks of excellent quality, long, round with
smooth ribs. It develops pink
speckling on a light green stalk with the pink color being more intense at the
bottom of the stalk, fading to a solid green near the top. Victoria is commonly used for forcing.
Strawberry is very similar to Victoria, and may be the same variety.
MacDonald is another "pink" type that produces well.
German Wine is similar to Victoria but slightly more vigorous and more
intense in color, typically with a darker pink speckling on a green stem.
Riverside Giant, a cold-hardy, vigorous producer with large diameter,
long, green stalks.
For more information on varieties, see the Varieties chapter of
The Rhubarb Compendium.
Planting stocks of the most desirable varieties are difficult to obtain
in large quantities. Limited
quantities of certain varieties may be available from:
Miller Nurseries, 5060 W. Lake Rd., Canandaigua, NY 14424.
St. Lawrence Nurseries, 325 State Hwy. 345, Potsdam, NY 13676.
Smith Nursery Co., PO Box 515, Charles City, IA 50615 (wholesale).
Territorial Seed Co., P.O. Box 157, Cottage Grove, OR 97424-0061.
W. Atleee Burpee, Warminster, PA 18974.
West Union Gardens, 7775 NW Cornelius Pass Rd., Hillsboro, OR 97124; 503-645-1592.
Rhubarb plants may be produced through tissue culture. Although more
expensive, rapid increase via tissue culture may be possible by contracting with plant propagators
having tissue culture capabilities.
Rhubarb seed is not normally used to establish production fields.
Healthy, vigorous 3 to 4-year
old crowns are divided to obtain two or more buds per seed-piece. Five or six
year old crowns
will yield 8-10 good quality pieces.
Both red and green petiole varieties are available. Only the red
varieties are important. As much
as possible, obtain planting stocks only from reputable nurseries. When
rhubarb planting stock is
obtained from old fields, care should be taken to insure that crowns are free
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. Plant crown divisions in March or
April or as soon as soil conditions allow.
Use a well-drained but moisture-holding soil with a pH of 5.5 to 7.0.
The 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. Choose fields free of problem perennial weeds.
A soil test is the most accurate guide to fertilizer requirements. The
are general guidelines:
Liming should be done if the pH is below 5.6.
Manure at 25 to 35 tons/acre 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.)
Fertilizer - In year of setting apply the following:
Nitrogen: 70-80 (N) 70-80 lb/acre
Phosphate: 70-80 (P2O5) lb/acre
Potash: 140-160 (K2O) lb/acre
In subsequent years apply the following:
Nitrogen: l40-160 (N) lb/acre
Phosphate: 70-80 (P2O5) lb/acre
Potash: 140-160 (K2O) lb/acre
Boron (B), Apply 1 to 2 lb/acre. A foliar application of 0.5 lb/A may
also be made in early spring when plants are 6-8 inches tall.
Nitrogen fertilizer applications should be split into 3
sidedressings: 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.
The crown pieces are planted 3-6 inches deep, 2-3 feet apart, in rows
about 4-6 feet apart or in a
4x4 foot grid to allow for cross cultivation. The most common spacing in Oregon is 2' x 6'.
About 3600 plants would be needed per acre.
Rhubarb intended for mechanical harvest is planted 18 inches apart in rows 4
feet apart. This spacing would require about 7200 plants per acre.
Irrigation is usually not necessary during the spring harvest of April
and May in the Willamette
Valley. Maintain adequate soil moisture after the harvest season, to insure
good regrowth. A
second crop may be harvested in early to mid July after which the field may be
regrown or not
harvested and allowed to go dormant through late July and August. If
harvested in July, growth
will be delayed the following spring.
Soil type does not affect the amount of total water needed, but does
dictate frequency of water
application. Lighter soils need more frequent water applications, but less
water applied per application.
Rhubarb requires a dormancy period of temperatures below 40 F to break
stimulate the production of leaf petioles. Winter conditions in the Pacific
northwest easily meet
this requirement. When temperatures begin to exceed 45-50 F, crown buds begin
Early growth may be enhanced ten days to two weeks by the use of clear plastic
row covers which may be applied in early February. Allow sufficient slack for stalk
growth. Gibberellic acid
may also be injected into the crowns at 0.0l grams of GA3 (Pro-Gibb) per
crown. Injection is accomplished by using a custom-built, pneumatically activated, hand-operated
injector wand that delivers the correct dosage when it is pushed into a rhubarb crown.
Harvest may start as early as mid-March. At the end of petiole harvest (May or June) new shoots will emerge.
These will provide the
reserves for the following year's crop. If growth and moisture reserves are
adequate, a second
harvest may be made in August or September, but stalks must be firm and not
Rhubarb crowns may be harvested for "forcing" indoors to obtain stalks
for market earlier than
would be possible from the field or during the off-season. This involves the
digging of entire
crowns and selecting the largest to place in a "forcing house" at a later
date. Harvest of forcing
rhubarb usually begins in early January.
Crowns used for forcing are usually two or three years old. Large
crowns with a few large buds
are preferred. Crowns from fields that have been harvested for outdoor
production are not
recommended for forcing, due to the poorer yields that result.
Structures used for forcing vary considerably in size and type.
Consideration needs to be given if
equipment will be used inside the house, and method and cost of heating.
Rhubarb crowns in the field must be allowed to go into dormancy and
exposed to a certain rest
period before any forcing is possible. This requires exposure to temperatures
between 28 and 50
F for 7 to 9 weeks at the end of the growing season. Exposure to temperatures
below 28 F
reduce yields, while temperatures above 50 F contribute nothing to the
required rest period. The
amount of cold required before forcing can be started is referred to as "cold units." Cold Units
are the accumulated number of degrees below 49 F (and above 28 F) as recorded
Varieties such as Victoria and German Wine will require about 470-500 cold
units to force
Crowns may be subjected to cold treatment for accumulation of the
required cold units either in
the field, or in the forcing structure. In Oregon and western Washington
where soil conditions
allow, crowns are most commonly allowed to reach their rest period in the
field, then plowed up
for placement in forcing structures and forcing in mid-December. In other
areas, where fall
temperatures are more extreme, crowns may be dug in October or November and
left in the field
until excessively cold temperatures require their removal to the forcing
acid may be used to substitute for a possible lack of cold induction and to
increase uniformity of
At the appropriate time, crowns are plowed out of the ground and placed
on the earth floor of the
forcing structure as close to each other as possible. This requires about 1
square foot per crown.
The spaces around each crown is filled with soil, leaving walkways where
needed. At the time
forcing is desired the soil is wetted and temperature raised to 56 F. This
temperature has been
found to produce the best yields. Temperatures between 50 F and 56 F produce
more intense red
color but slower growth. Temperatures below 50 F may reduce yields, and those
above 60 F
result in pale stalk color, a faster growth rate, and also may result in lower
yields, especially if
exceeding 65 F. Regardless of the temperature, stalk color becomes less
intense as the crowns
Forcing rhubarb is usually picked about twice a week for about 4-6
weeks. Separate forcing
structures may be sequenced, by starting forcing at different times, to
provide forced rhubarb into May when field rhubarb becomes available.
It is important to maintain good, but not excessive, soil moisture around
the roots in the forcing
structure. Production drops off dramatically when the soil becomes dry.
Yields of rhubarb depend on the number of pickings, and the age and
condition of the field. In the
Pacific Northwest yields may range from 6 to 12 tons per acre for red
varieties. A yield of 8-10 tons/acre is most common at the first harvest. Fields may be
harvested a second time with yields generally reduced by 50 percent from the first harvest.
Green varieties tend to yield more. A well-maintained field may remain productive for 15 or more
Rhubarb in Oregon is all hand harvested. For processing, both ends of the petiole
are trimmed so that no leaf tissue remains. For fresh market a small amount (1/4 inch) of leaf tissue
is usually left attached to the petiole and the basal end is not trimmed. Splitting of the
petiole will be more serious if the entire leaf is removed.
A machine has been developed by USDA
Agricultural Engineers and may be available through the Wilde Manufacturing
Co. of Bailey,
Michigan. Fields intended for machine harvest are planted at much higher
in-row populations than fields for hand harvest (as noted above).
Stalks should not be pulled during the first year of growth. Stalk
color is best after the field is 2
to 3 years old. In subsequent years, harvesting can be expected to start in
March and to end in
June. This will vary with management practices, with the variety being grown,
and is somewhat
driven by market demand.
Plants should not be over-pulled at any time, as a certain amount of
foliage is required for the
development of the present crop as well as next year's crop. A well-cared-for
field will last for l0-15 years or longer.
In the Willamette Valley, early rhubarb is harvested for processing from
April 25 to May 25. The
prime harvest period is from April 25 to May 15. Late rhubarb is harvested
from June 25 to July
25. The prime harvest period for late rhubarb is June 25 to July 7.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Store at 32 F and 95 to 100% relative humidity. Fresh rhubarb stalks in
good condition can be
stored 2 to 4 weeks at 32 F and high relative humidity. Rhubarb can be
air-cooled, and the temperature of the stalks should reach 32 or 33 F 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
Moisture loss in storage will be much
less if the bunched or loose stalks are packed in crates lined with perforated
Fresh rhubarb cut into 1-inch pieces and packaged in 1-lb perforated
polyethylene bags can be
held 2 to 3 weeks at 32 F with high relative humidity.
Rhubarb is commonly packaged in 20-lb cartons, place pack; or, 1-lb film
bags, in cartons containing 10 bags each.
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