Growing Rhubarb

Rheum rhabarbarum, a member of the buckwheat family, is a native of Manchuria. Several closely related species, brought back by plant collectors from various parts of Asia, are grown for their spectacular ornamental leaves. But rhubarb is the only member of the family that is used for food.

Because rhubarb is so hardy and will survive almost total neglect, it is often left to it's own devices in preference to other more demanding vegetables. This is a pity, because with minimal treatment at the correct time it will flourish and provide you with delicious stalks at a time when little else is cropping in the garden.

Rhubarb requires temperatures below 40­ F (5 C) to break dormancy and to stimulate spring growth and summer temperatures averaging less than 75­ F (25 C) for vigorous vegetative growth. The Northern U.S. and Canada are well suited for rhubarb production.

One word of warning - do not eat the leaves of rhubarb - they contain oxalic acid which is definitely poisonous to humans.

Site Location

If possible, it's best to grow rhubarb in full sun, but is fairly tolerant of partial shade. They will remain in the same position for up to 10 years and the soil immediately surrounding the plant cannot be dug, so position it with this in mind.

Soil Preparation

Tolerant of most soil conditions, rhubarb grows best in a neutral soil which has been dug to a depth of 60cm (2 feet) or more. Incorporate as much organic matter as possible during the digging because it must last the life of the plant - rhubarb will not tolerate soil disturbance once established. The site should be prepared about 4 weeks in advance of planting to give it time to settle.

Rhubarb is tolerant of soil acidity but does best in slightly to moderately acid soil. The crop can tolerate soil pH as low as 5.0; however, maximum yields are attained at a pH of 6.0 to 6.8. Liberal quantities of fertilizer are needed and your yield will significantly increase with the addition of a general all-purpose fertilizer (10-10-10).

The best way to increase soil health is to incorporate organic matter and compost directly into the soil and till well before planting. This will also help to maintain soil moisture during hot periods. Be careful to use organic material free from weed seeds.

Be especially careful to remove all weeds at the preparation stage - once rhubarb is planted, it will be very difficult to get rid of them. No herbicides are registered for use on rhubarb. Small areas of perennial weeds can quickly build up to serious proportions. To prevent this, all perennial weeds should be killed the year before planting.

When to Plant

Rhubarb can be grown either from seed or as plants purchased from your garden centre. The problem with rhubarb grown from seed is that it takes a year longer to produce stalks and even then, the plants are not guaranteed to be true to type - it's a gamble which takes three years before you know if you have succeeded or failed. For this reason, we do not recommend the 'seed' route.

Rhubarb plants are available all year round at some garden centres, although by far the best time to plant rhubarb is late autumn to early winter - December is a good month.

How to Plant Rhubarb

Rhubarb is normally sold in garden centres as one year old plants (known as 'crowns') of a particular variety. Rhubarb five years or more old can be lifted and split into three or more 'crowns' - see the later section on 'how to divide rhubarb'. Both types should be planted in the same manner.

Prepare the soil as described previously, and dig a hole a little bit wider than the plant. The depth should be such that the top of the plant is 2.5cm (1 inch) below the soil surface. Fill in around the plant with soil, gently firming it down to ensure no air pockets remain. Space rhubarb roots 24 to 48 inches (30 to 60 cm) apart in rows 3 to 4 feet (1 m to 1.3 m) apart.

Water well if the conditions are dry. Spread a mulch (garden compost or other well-rotted organic material) around the plants, but not directly above where the crown will emerge in a month or so.

Three plants should be sufficient to meet most needs - the spacing between plants should be about 75cm (2ft 6in) for varieties such as Cawood Delight, Victoria, Ruby and Canada Red. However, some varieties such as 'The Sutton' need a spacing of about 1.2m (4ft) - ask at your Garden Centre when buying any other varieties.

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