Growing Rhubarb in Tasmania
Rhubarb, a close relative of swiss chard and beetroot, is grown for its edible stalks. The leaves contain oxalic acid, poisonous to humans and dogs, although they can be composted, or boiled to make an aphid spray. It’s a hardy perennial, so it can survive the cold Tasmanian winters and will provide you with many years of juicy stalks which are perfect for pies and desserts. It needs plenty of water and feeding and will produce the best harvests in the temperate spring and autumn weather. There are green and red-stalk varieties available, they taste very similar, but most people seem to prefer the look of the red stalks.
Expecting red rhubarb? Not all varieties yield red stems, in fact many produce only green ones! These are just as tasty as the red ones, but green rhubarb usually becomes dormant in winter, while red varieties produce all year round. Consider this when selecting your plants.
Rhubarb can grow into a very big plant, so don’t overcrowd your plants. Give them enough space to spread and grow.
Rhubarb needs some shade in the afternoon to protect it from the harshest afternoon sun.
Dig the soil over (break it up) a month or so before planting, if possible. Then prepare the soil with lots of organic matter and spread a 10 cm layer of manure and then dig that in. A week before planting, dig the soil over again, adding some blood and bone. All this will help the soil to drain better; a well drained soil will ensure that the rhubarb does not rot at the roots. Eliminating weeds will minimise competition and improve yields.
Plant seeds once all danger of frost has passed and its consistently warm.
Soak in warm water for a few hours before planting.
Rhubarb can be started from seed quite easily, but the plants take up to 3 years to become established and reach a size that you can harvest from. So, it’s more common for rhubarb to be planted from crowns. If you want to plant a large patch, seeds are definitely a cheaper way to go. Plant seeds into trays or well-prepared beds. They should take 2-3 weeks to sprout and the soil needs to be kept moist right through this time. Once they are established thin them or transplant into the garden at their final spacing.
Plant crowns during winter or early spring while they are dormant (or at least growing slowly)
When you plant the crowns, leave the ‘eye’ (where the leaves emerge) at ground level and press the soil around the roots in firmly. Rhubarb has a voracious appetite; sprinkle some blood and bone at the base while planting, or even better, feed with some liquid blood and bone which will be fast acting and much more easily absorbed in the cool August weather.
Try to avoid harvesting the stalks for the first year, to give the plant the opportunity to establish; this will give you bigger yields in subsequent years.
Clumps can be divided in winter. Lift the crowns and separate them to make new plants. Separate the crowns at the three year mark to keep the plants healthy and productive.
Flowering spikes will appear if the plant is stressed, break them off as soon as the appear and treat the plant with regular deep waterings, a liquid fertiliser and a good mulching. Flowering spikes also suggest that crowns need to be divided; do this in July. Cut away any black roots, these are dead, and divide into pieces with three shoots on each piece.
Leafy rhubarb thrives with regular watering. Give the plants a regular thorough soaking, at least weekly in summer, in the cooler evening weather. If the stems are flopping over, or there are flowering stems, the plant is suffering heat stress; make sure that the plants are watered regularly, and mulch well to keep them cool and the roots moist.
Potash will improve the yield and potentially the colour of the stems, although many varieties only yield green stems, which cannot be forced but are just as tasty. Choose your variety carefully if colour is important to you. Regular liquid fertiliser should also be applied.
Organic matter, such as straw and grass clippings, should be spread around the plants, keeping close to the base; soak this in liquid manure or fish emulsion to provide lots of nitrogen to feed the stems and suppress flower production.
Give your rhubarb a good mulch to keep the soil cool and moist through the hot summer months. Remember to keep topping up your mulch as it breaks down into your soil.
Mulch well with straw or any available organic matter, and wet with liquid manure or fish emulsion to keep roots moist and also suppress weeds. Keep mulching throughout summer to prevent heat stress.
Rhubarb can be harvested at any time of the year. Just make sure the stems are big enough to use. Rhubarb usually produces most abundantly during autumn and grows very slowly during winter. A severe frost may cause your plants to die back in winter, but don’t worry. Rhubarb is incredibly hardy and will bounce back as soon as the weather warms up again.
Once your stalks reach a useable size (usually about the thickness of a finger) you can harvest them. Hold the stalk firmly and pull it down and away from the plant. Leave some stalks on the plant so that it keeps growing vigorously. Remember, the leaves are poisonous to people and animals, so discard them and only eat the stalks.
Thin and weak stems are a sign the plant is struggling to maintain production- stop harvesting and give a boost of liquid fertiliser to give the plant a chance to recover.