Rhubarb
can be propagated by several means: Dividing the root mass, growing rhubarb from seeds, or
by Tissue Culture. Of course, you can always purchase rhubarb plants or
rhizomes ready to plant in your garden. See the list of
sources for a few of the mail order companies that sell rhubarb.
Rhubarbcan propagated by planting pieces
obtained by dividing the crown. Pieces are taken from 4-5 year old crowns. You can divide
earlier if you desire more plants. Dividing can be done either in the spring or the fall
with equal success, but I have found early spring is best. I wait until early growth is
just starting so I can see where to best divide the root mass. Dig up the crowns and roots
being careful not to damage the crown. Cut the roots into 4 to 8 pieces. It is recommended
to split dormant crowns between large buds or "eyes" so that at least a 2-inch
cross section of storage root is left with each bud. Be careful of is not to break off the
delicate buds which are easily broken, but otherwise the roots are quite tough and will
tolerate quite a bit of rough handling. Very small buds will give small plants for the
first few years after planting, while four to ten new roots can usually be obtained from
crowns that have been grown a few years. Root pieces should be protected from drying or
freezing if they are not to be planted immediately. When dividing crowns for re-planting,
it is important to mark the vigorous plants in June and use them as planting stock the
following spring. Crowns should not be divided from diseased plants.
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| This is the original plant last summer (1996). It
is 4 years old. It doesn't really need to be divided but I want to move it to a different
location so I will take the opportunity now. As shown here the plant is over 3 feet (90
cm) in width and the leaves are about 1 foot (30.5 cm) across. This plant is the Victoria
variety which produces very green stalks and grows rather vigorously and quite large. |
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You can divide rhubarb with equal success in either
early spring or late fall. Shown here is the plant in early spring (mid March) 1997.
Spring came early to Maryland this year so the rhubarb is growing already. This makes it
easier to divide but I think its more stressful on the plant. Next time I will divide them
in the late fall. The early growth shown here is about 6 inches (15 cm) tall.  |
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| Dig up the root ball being careful to not destroy
too many roots. Shown here is the same plant as immediately above. Notice that some of the
roots extend from the rhizome for 16 inches (40 cm) or more. You can't help but break some
of these, but that's ok. Here I show you where I plan to make the first division. This
plant has two major clumps of "buds". You can see this by looking at the clumps
of petioles (stems). There are 8-10 possible plants here if I divide carefully. |
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| For the first division I simply use a shovel to cut
through the root/rhizome cluster between the "buds" of new growth. Careful study
of the cluster will reveal old, rotten, rhizome and roots. This is a good area to cut
through. After I separate the 2 clumps I repeat this several times. Each new plant will
have a small rhizome, some roots, and a "bud" of new growth (because its
spring). |
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| I have now divided this into eight new rhubarb
plants. Some are large chunks of rhizome, others are just little root/rhizome/bud slivers
about 3 inches (8 cm) in length. All of these will grow into mature, healthy plants if
properly re-planted. |
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| Before I re-plant the divisions I examine the
rhizome/root area for excessive rot and decay. If there is a significant amount I would
discard this division. Here there is very little rot and I cut that off. There will
usually be some rot as this is part of the normal growth of the plant. You can also see
how large the rhizome/root mass is. Some old (10 years old more more) plants can have root
masses that are 3 feet (90 cm) in diameter and 1 foot (30 cm) deep. This is a young plant
by comparison. |
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| Here is one of the divisions in its new home. Notice
that I have planted it in a mixture of garden soil and compost (50%). Rhubarbs like
compost! Be sure to water well and check frequently. I will cut off the largest leaves on
this division as they will only drain the strength from the plant and they will probably
wilt and rot anyway. The new plant needs its strength for developing new roots. |
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Rhubarb plants may be started from seed. Plants started from seed typically take
2 years to get a harvest, although in the proper climate one can get satisfactory results
in one growing season. Also, propagation of rhubarb from seed is not recommended, as
rhubarb seedlings do not retain the characteristics of the parent plants
(see comments on Varieties).
It is best to propagate with planting
divisions obtained from splitting the crowns as described in the next section.
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| Figure 8.1: A Rhubarb Seed
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Rhubarb seeds can be purchased mail order from a number of
companies (see Sources). The seeds are encased in a
rather large paper-like shell. Soak the seeds in water for a few hours before planting.
Plant the seeds in a suitable planting mixture. These seeds were sown in a commercially
available mixture, 2 seeds per pot. I planted them in peat pots to making transplanting
them easier and then put them in a sunny window. A heating cable will help speed the
germination if the room temperature is below 70 degrees F.
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Rhubarb seeds
germinate quickly. Shown here is a tiny rhubarb seedling at 10 days after planting (March
1997). At this point I will pinch off all but one seedling (I planted 2 seeds per pot,
expecting the germination rater to be 50%). If I had wanted to grow these as annuals
I would have started them sooner, like in the fall of the previous year, so I could plant
them outside in early April. |
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As the weather turned warmer (45 degrees F
during the day, near 32 degrees F at night) I transplanted the rhubarb seedlings outdoors.
I planted them in a mixture of 50% compost and 50% garden soil. |
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Protect the seedlings from the bright sun.
Rather than harden off the seedlings by gradually increasing their exposure to sunlight, I
fitted the rhubarb plants with tiny little paper hats. These only lasted for about a week
but that was long enough. |
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Shown here is the same seeding shown above but
in 60 day since planting (30 days after being transplanted outside). The plant is finally
beginning to look like a rhubarb plant. At the end of the growing season these
plants were about 12 inches () tall and had about 15 leaves each. Not quite enough
for a harvest. Next year maybe. |
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Rhubarb can be grown as an
annual from seed in areas that have a cool season (like a cool winter in the southern
parts of the US). Plant seeds in nursery pots, transplant outside when the plants about
3-4" tall. Harvest stalks as they mature. Be careful to not over water it as rhubarb
can get root rot if the ground is too wet.
ECHO
("Educational Concerns for Hunger Organization") has
claimed good luck with planting rhubarb seed in August and harvesting in March-May. Seed
grown rhubarb will have fewer plants with the intense red color stems we are used to, but
tasting a pie grown from subtropical rhubarb can help one overlook that quickly! You will
probably get a mix of plant colors ranging from green through pink with a few plants with
red or partly red stems. The variety Victoria is extremely productive. Seeds can be
purchased from Park Seed Co. Greenwood South Carolina, USA.
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| Figure 8.2: Rhubarb Seeds
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Rhubarb is often commercially propagated by tissue culture. The Kentville Research
Center has been the site of research on propagation of rhubarb. The current interest in
growing rhubarb on a commercial scale has been stimulated by increasing demand for it, but
growers are faced with two difficult decisions: What are the best varieties? Where can
healthy planting stock be found? The Kentville Research Center is providing assistance
through the technique of micropropagation which consists of starting test tube cultures
from minute growing tips (meristems). These meristems are dissected out of buds and when
provided with proper nutrients and plant hormones will grow and multiply. The benefits of
this propagation technique include disease free plants and year round rapid
multiplication. Rhubarb micropropagation techniques are now available for commercial
tissue culture labs to exploit and rhubarb growers can look forward to a secure supply of
healthy plants.
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For more information:
Tissue culture in the Home Kitchen - http://www.labs.agilent.com/botany/public_html/cp/slides/tc/tc.htm
Readers of The Rhubarb Compendium may be interested in...
TheComplete Book of Plant Propagation
Graham Clarke
Detailed text covers the history of plant propagation, a study of recent developments,
and specific instruction on techniques such as seed sowing undercover,
raising plants from spores, through to grafting, budding, and micropropagation.
About half the book comprises plant entries with specific techniques
detailed.
[b10]
Footnotes: