Cotoneasters are the 'super plant' of 2021, so how do you grow them?

A new RHS science paper found that Cotoneaster franchetii is the latest ‘super plant’ to help boost the environment and improve human health

Morgan Lawrence 18 February 2021 • 9:34am

Cotoneasters are the 'super plant' of 2021, so how do you grow them? — Cotoneaster is so common that it can easily be overlooked, but recent research suggests it has more benefits than expected Credit: Alamy

Thanks to findings from a recent Royal Horticultural Society study, Cotoneaster franchetii is being hailed as the latest 'super plant' of 2021.

While investigating the effectiveness of hedges as air pollution barriers, researchers discovered that in traffic hot-spots, cotoneasters (a genus of flowering plants in the rose family) are at least 20 per cent more effective at soaking up pollution compared to other plant species.

In November 2018, the British government announced that poor air quality was the largest environmental risk to UK public health, and that the cost of health impacts of air pollution was likely to exceed estimates of up to £20 billion. Findings from another RHS survey of more than 2,000 people found that air pollution affects one in three Brits.

"On major city roads with heavy traffic we’ve found that the plant species with more complex denser canopies, rough and hairy leaves, such as cotoneaster, were the most effective," said Dr Tijana Blanusa, RHS principal horticultural scientist and research lead for the study.

Commonly found in gardens across the UK, the Palaearctic native is a tough, evergreen shrub displaying small and oval-shaped leaves on arching branches. When flowering in May and June, the five-petalled flowers are tinted light pink and cream; while in autumn, the branches are laden with deep orange-red berries.

These useful shrubs can vary in size and height. There are evergreen, semi-evergreen and deciduous varieties; some are prostrate ground-covers, while others grow to be substantial shrubs, or even small trees. Many can make useful hedging plants, while others can be trained flat against a wall; a few can be grown as weeping standards.

Matthew Pottage, curator of RHS Wisley and shrub expert, was happy to hear the news. "Cotoneaster is such an easy plant group and can be spotted in gardens across the UK," he says. "They're unfussy. I find that planting them in full sun yields the most flowers and berries but I've known some to tolerate part-shade, too. You can leave the shrub to do its thing most of the time; if you're struggling with a cotoneaster, you're probably gardening on concrete!"

Pottage recommends planting the shrub in spring or autumn although you can also plant them in summer. If you do the latter, "simply keep the roots watered through a dry spell," he says. When pruning, which you only need to do if the plant has outgrown its space, he advises cutting the main branches right back to the centre of the plant. "Don't be afraid of causing damage. It will grow back perfectly fine."

Cotoneaster salicifolius 'Pink Champagne' is a favourite of his for its small white and pink flowers in spring and peach-coloured fruit in autumn. "It has a lovely spread and branch structure," he says. "Often the fruit hangs on until the end of autumn and early winter." While Cotoneaster lacteus, with its silvery white underside to its leaves and bright red berries, is another popular choice.

Val Bourne's guide to growing Cotoneaster lacteus

Cotoneaster lacteus fit to bust with berries Credit: IStockPhoto

Cotoneasters are hardy and tolerant of both of pollution and of windy positions. C. lacteus can survive in shade, but it will only set lots of berries in a sunny situation. The mature shrub makes a wide mound that can measure 20ft across and 12ft high, so it is not suitable for a small garden.
It is rugged enough to be grown on a boundary or as a 6ft to 10ft hedge, in which case leave a 2ft to 3ft gap between each plant. Trim back any vigorous shoots after flowering and shape in late February.
Propagate by semi-ripe cuttings. Pull away vigorous, healthy side shoots in July or August. Trim these off below a leaf joint, using a sharp knife, and remove the lower leaves, then insert the cuttings into gritty compost and place them in a cold frame. These should root by the following spring.
Cotoneaster lacteus comes true from seed. Gather the berries in late spring and sow them in compost, using chicken wire to protect the seeds from mice. Place the pots in a cold frame and the seeds should germinate, after a period of stratification (exposure to cold), the following spring.
Cotoneasters are generally robust but, as with other fruit or pome-bearing members of the rose family, they can suffer from fireblight. This bacterial disease is carried by wind, rain splash, pollen and insects. The leaves turn blackish-brown, then shrivel and die on the stem. There is no chemical control. Remove the whole plant or cut back to clean wood and burn the diseased debris.