Feeding rhubarb & other rhubarb care tips
As a hungry perennial plant, rhubarb benefits from some extra nutrition. Discover how and when to fertilise rhubarb for a bumper harvest.
Grown for its edible stems, rhubarb (Rheum x hybridum) is generally easy to care for. However, as a hungry feeder, it is important to provide the essential nutrients to support its growth during the growing season. Read on to find out which fertiliser to use and when to apply it to ensure that you have a bountiful rhubarb crop come spring.
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Feeding rhubarb
As a perennial vegetable, rhubarb dies back in the winter before putting on strong new growth come spring. When mature, rhubarb plants are large and some rhubarb varieties can grow more than 1m high and wide. Hence, it is no surprise that they use up a lot of energy producing their large stems and foliage. To support their growth and help provide the nutrients required, you can feed rhubarb with a fertiliser, especially if the soil is poor. If you grow rhubarb in a pot, applying a fertiliser is particularly important because, due to the limited quantity of soil, the nutrients can quickly run low or leach out of the pot when watering.
When to feed rhubarb
The best time to feed rhubarb is in spring or early summer to support the new season’s growth. Slow-release fertilisers or organic matter tend to break down slowly and can feed plants for around 2 to 3 months, meaning that one application may be enough for the year. If your rhubarb appears to be struggling, you can apply a second dose in early summer. However, it is important not to fertilise rhubarb with a nitrogen-based fertiliser after the end of June, as this may encourage new growth when the plant wants to enter its dormancy in the autumn.
You can also fertilise rhubarb at the time of planting. Before planting rhubarb, you can prepare the ground by removing any weeds and adding around 40L per sqm of well-rotted manure, garden compost or a balanced granular fertiliser to the soil to enrich it.
Best feed for rhubarb
Along with the right timing, applying the correct rhubarb fertiliser is key to supporting its growth. When it comes to fertilising rhubarb, you can either apply organic matter, such as homemade garden compost or well-rotted manure, or an organic concentrated fertiliser in granular form to the soil. Garden compost and well-rotted manure generally contain low levels of nitrogen, phosphates and potash (NPK). However, they also have the bonus of increasing the percentage of organic matter in the soil, adding good bacteria to the soil and improving soil structure.
Along with organic matter, you can apply an organic concentrated fertiliser in late spring or early summer to support the growth. You can use a general-purpose fertiliser like our Plantura All Purpose Plant Food to feed rhubarb. It is made from 100% natural ingredients and will feed the plant for up to 3 months.
- Perfect for a variety of plants in the garden & on the balcony
- Promotes healthy plant growth & an active soil life
- Long-lasting fertiliser that is free from animal products - child & pet friendly
You can also use spent coffee grounds to fertilise rhubarb. Coffee grounds generally contain the key essential nutrients of nitrogen, phosphorus and potassium but can increase the acidity of the soil when added in large quantities. When fertilising rhubarb with coffee grounds, a handful or two spread around the base of the plant and gently worked into the soil is generally sufficient and should not affect the pH levels of the soil adversely.
Homemade garden feeds, such as nettle (Urtica) tea, which is high in nitrogen, can also be used to feed rhubarb in spring or early summer. You can make nettle fertiliser by steeping chopped-up young nettles in a large bucket of water for around 3 to 4 weeks. Once ‘brewed’, you can dilute the solution at a ratio of 1 part nettle tea to 10 parts water and apply it to the soil around the plant.
How to fertilise
Here are our recommendations for feeding rhubarb:
- Enrich the soil with well-rotted manure or garden compost prior to planting
- In spring, apply a generous amount of organic matter around the plant and carefully work into the soil, avoiding the crown and roots
- In late spring or early summer, you can apply a general fertiliser or nettle tea to support growth throughout the summer
Rhubarb care
Rhubarb plant care is generally straightforward if it is planted in the right place and receives enough moisture and nutrients during the growing season. However, if you grow rhubarb in pots, more care is needed to ensure that the soil does not dry out or run out of nutrients. As such, regular watering and following a fertilising schedule are important care measures for rhubarb in pots.
Watering
Rhubarb prefers a moist but free-draining soil and regular watering is required during the warmer months. However, rhubarb does not tolerate saturated soil, so any sites prone to waterlogging or overwatering should be avoided. When watering rhubarb, it is important to water to the base of the plant avoiding the foliage, as this can help prevent fungal diseases from occurring.
Mulching
Mulching is a great way of feeding the soil, suppressing weeds and conserving moisture during the summer months. March is the ideal time to mulch rhubarb, as the spring rains will direct the nutrients down towards the roots. You can apply bark chippings, garden compost, leaf mould and well-rotted manure as a rhubarb mulch. To apply a mulch, simply spread a layer of the organic matter 5 to 7cm deep around the base of the plant. When mulching, it is wise to leave some space around the plant, as covering the crowns can lead to crown rot.
Tip: for an earlier and even sweeter crop, you can try forcing rhubarb under a pot.
Small rhubarb stalks
If you find that your rhubarb stalks are small or weak, this can be for several reasons. If a lack of sun or nutrients is resulting in poor growth, you can try moving any container-grown rhubarb to a south-facing position or fertilising the rhubarb. Incorrect picking of the stems can also lead to reduced vigour. It is important when harvesting rhubarb that any picking ceases after July at the latest to allow the rhubarb to recuperate before winter. As rhubarb plants age, their vigour can also decrease. It is advisable to propagate rhubarb plants by dividing them every 5 years to encourage strong and healthy plants. Finally, allowing rhubarb to flower and go to seed can also use a lot of the plant’s energy and lead to poor yields. If flower stems appear on your rhubarb, remove the whole stalk swiftly to divert the energy back into the plant.
Rhubarb diseases and pests
Generally, when given the right growing conditions, rhubarb grows problem-free. However, as with most other crops, rhubarb can fall prey to some diseases and pests. Perhaps the most common rhubarb pest is slugs and snails (Gastropoda). Slugs and snails love to devour the soft new foliage and will even eat larger leaves. You can help prevent slug and snail damage by encouraging predatory wildlife into your garden, picking them off by hand and laying barriers around the rhubarb crowns.
Crown rot can be an issue when growing rhubarb in heavy or compacted soils and those that are prone to waterlogging. Causing poor growth and the crowns to rot, there is no control measure for crown rot apart from digging up affected plants to dispose of carefully. Preventative measures against crown rot include growing rhubarb on a free-draining soil, avoiding overwatering and leaving the crowns clear when applying a mulch.
To ensure that your rhubarb continues cropping for several years, it is important to harvest rhubarb in the correct way. Learn more about how and when to harvest rhubarb in our separate article.
