Rhubarb is a popular home-grown vegetable. Unlike most vegetables, Rhubarb is a perennial. This means the same plant will return a crop for many years (around 10 to 15 years).
Growing Rhubarb is relatively simple in cool climates. Rhubarb is quite a hardy crop and can withstand lack of water. Rhubarb will survive and produce good yields with little tending apart from the application of fertilizer.
Preparation
Rhubarb is a crop for which it is definitely worth the effort to prepare the soil before planting. This is because Rhubarb will rely on the soil for many years to come, not just this year.
Dig the soil to a good depth and introduce a good amount of organic matter into the soil. Common forms of organic matter include well rotted manure or garden compost. This organic matter will provide soil nutrients improve the soil structure. Dig the organic matter in a month before planting to allow time for the soil to consolidate.
Rhubarb doesn’t like its roots disturbed once established. To avoid heavy weeding at a later stage, remove as many weeds from the soil as possible before planting.
Sowing
Rhubarb is best grown from rhubarb crowns rather than growing from seed. Plant Rhubarb in early spring. It requires low temperatures (around 40 deg F) for it to break its winter dormancy and renew growth.
Plant the Rhubarb crowns about 10 cm below the soil surface. The crown bud should be about 5 cm below the soil surface. Any young shoots that exist should just break the soil surface.
Spacing of the crowns will depend on the variety. Around 60-80 cm spacing is right for many varieties such as the popular Victoria.
Position
Rhubarb will grow well in part shaded areas. Rhubarb does not grow well in high temperatures.
Avoid positioning in frost pockets. A severe frost will have a damaging effect on Rhubarb. It may cause the oxalic acid from the leaves to enter the stalks. For this reason you should remove any stalks that have been affected by a hard frost. Place them on the compost heap where they will decompose. The decomposition that occurs in your compost heap breaks down the oxalic acid.
Soil type
Rhubarb can be grown in acidic soils down to about pH 5.0. It grows best in slightly acidic soil of about pH 6.0-6.8.
Rhubarb likes a well-drained, fertile soil that contains a good amount of organic matter such as well-rotted manure or compost.
If the soil is not well drained, then water logging can result in the crowns rotting.
Tending
Rhubarb requires little tending, but with just a little effort, you will achieve a much better quantity and quality of crop.
You can bring the growing season of Rhubarb forward by covering the crowns with a cloche in early spring. A cut clear plastic bottle will act as a cloche or you can get one ‘made for the job’ from your garden center.
If flowering seed stalks develop then cut them as soon as possible. Seed and flower production will reduce the stalk yield. This is because the plant diverts its energy into flower and seed production.
Make sure to weed around your rhubarb plants regularly as weeds can have a damaging effect on plant growth. Do not hoe too deeply and disturb the roots. Remove any leaves that have turned yellow or have fallen to floor level (such as in the picture below).
Adding fertilizer such as well-rotted manure each year will increase your rhubarb yield significantly. Fertilize in early spring before plant growth and also before the end of autumn. The fertilizer will:
- increase the availability of nutrients in the soil
- act like a mulch
- improve the water retention properties of the soil
- reduce weed growth.
If adding manure / compost be sure not to cover the Rhubarb crowns as this can lead to them rotting.
Do not use fresh manure as this can burn the crop.
After the first hard frost of winter, you should remove any remaining stalks and add them to your compost heap.
Dividing Rhubarb
You may want to thin your crowns every 4-5 years if they are getting overcrowded. You may also wish to use part of the crown to start another plant. When the stems of the plant begin to become thinner and they are looking crowded it is a sign that the plant is ready for dividing.
To divide the plant dig up the crown and then divide the crown into sections. Ensure that you have at least one bud and two inches of root on each section. You can often get about 4 to 8 new root sections from a crown. Divide Rhubarb crowns in early spring when new growth is just visible.
Harvesting
Harvest rhubarb either by cutting the stems at soil level or by pulling up the stems. You can harvest about 3 or 4 stems at a time per plant. Leave some stems remaining so the leaves can generate the plant’s energy and growth reserves.
Do not harvest the plant in the first year as the nutrients produced by the leaves should be channeled back into the roots. This will ensure a strong root system for stem production in the following years growth. In the second year harvest a couple of stalks per plant and after that you can harvest as normal.
DO NOT eat the Rhubarb leaves as they contain high levels of poisonous oxalic acid.
To promote more vigorous growth, in the next growing season, do not harvest all the leaf stalks.
Forcing Rhubarb
The harvesting season can be extended by ‘forcing’ the Rhubarb. Force Rhubarb in winter by covering the crowns with large pots which prevent light reaching the crowns. Forcing can be helped by adding straw or heat producing fresh horse manure inside the pot. Do not place the manure directly on the crown.
The pots pictured below are attractive terracotta forcing pots. You can however use any container that will prevent light reaching the Rhubarb such as an old bucket, box, trug etc.
Many people sing the praises of forced Rhubarb since it tends to produce very sweet and tender stems. It also produces a crop many weeks ahead of unforced Rhubarb. When you have picked the tender stems, take the container away. This lets the plant grow as normal, harnessing the sun’s energy to help it to replenish its energies. The next year, choose different crowns for forcing. This rotation of the forcing duties ensures that each plant has time to recover from the extra strain put on it from forcing.
Varieties
Rhubarb is available in both red leaf stalk and green leaf stalk varieties. Common varieties include
- Victoria – produces Green stems and is easy to grow
- Champagne – considered one of the best varieties for forcing – pale pink stems
- Goliath – thick stalked, high yield crop that is great for forcing.
How to use Rhubarb
Eat it with sugar – in crumbles, yogurts, pies, trifles, fool or just with custard.
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