When your rhubarb plants start throwing up flower spikes all is not well in the vegie garden, our resident green thumb PETER CUNDALL advises
Top tips for growing your own rhubarb
When long-established clumps of rhubarb start throwing up flower spikes, it’s usually a distress signal. The cause may be lack of water during summer, or extra-poor growing conditions, especially lack of sunlight.
However, the most common reason for persistent flowering and increasingly poor quality or sparse rhubarb sticks is old age. Clumps need to be lifted from the ground and root masses divided every five or six years to keep plants growing strongly.
The best time to do the job is when plants go into a form of dormancy in late autumn and winter.
There are several varieties of rhubarb, but they can be generally divided into two main groups, those with red stems and others with green stems.
The most popular green-stemmed variety is Victoria and is widely grown because it is vigorous and productive. The best red-stemmed rhubarb varieties are Sydney Crimson, Wandin Red and Ruby Red Dwarf, a compact form, ideal for growing in large containers
It’s impossible to make greenstemmed varieties of rhubarb turn red, al- though extra-cold conditions during winter can give some green sticks – which are always fairly thick and long – a pale, reddish base. Green varieties die back to the ground every winter.
Red-stemmed rhubarb tastes the same as green but looks nicer. The stems are shorter and not as thick, but are better year-round value because they continue producing light crops through winter.
Lifting an old, exhausted clump can take a fair amount of effort. The root masses – known as ‘crowns’ can be enormous. It is still well worth getting as much crown as possible from the ground.
I drive a sharp spade deeply around a
Red-stemmed rhubarb tastes the same as green but looks nicer ... and is better yearround value
clump, then use it to lever the entire root mass from the soil.
It can be a revolting sight of black, gnarled roots surrounded by enormous amounts of old, dead materials. Use a hose to blast off all soil and this isolates the healthiest, living divisions, easily identified by large, green buds at the tips.
Use the spade to cut up old crowns and get rid of all useless, half-dead material and old soft, partly-decomposed roots. An old clump can yield up to 20 or more new divisions, each with at least one healthy bud at the top.
Each of these divisions will create a new, highly-productive, healthy clump within two years – with even a light harvest during the first summer. The secret of success with rhubarb is lots of old, wellrotted manure.
I’ve had fantastic results simply by digging in two big bags of sheep manure into a square metre, adding half a bucket of pelletised poultry manure and a bucket of enriched biochar.
This make the soil extremely rich and fertile. After all, it is impossible to overfeed rhubarb. Just bury two divisions on either side of the enriched spot, leaving the buds just sticking up from the soil. Water in and leave to settle over winter.
The first shoots and unfurling leaves will appear in early September and with regular summer watering and added welldiluted fish emulsion every couple of weeks, growth will be extraordinary.
Red rhubarb clumps can be also divided, but it helps if older stems with large leaves are removed. Sometimes, newlyplanted rhubarb sends up the odd flower spike the following summer, but this is during the initial settling-in period.
Always remove these spikes as fast as they appear by giving each coarse, thick stem a good twist so it snaps off cleanly at the base.
Remember, rhubarb leaves are too toxic to eat, but if boiled in water for 20 minutes and liquid strained off and collected, it can be mixed with a few soap flakes to make an excellent aphid killer. And all toxicity disappears within hours.