They are the perfect tropical plant for cool climes
It’s a question I always dread: what’s your favourite plant? With an estimated 400,000 species to pick from, talk about a tough choice. But if I absolutely had to grow just one group of garden plants, it would be the hardy banana.
Despite finding their centre of diversity in the lowland tropics of south-east Asia, there are several banana species from the northerly (and especially high-altitude) edges of their range that experience significant levels of frost, and a climate on a par with that of many areas of Britain. The classic example of this is the Japanese hardy banana, Musa basjoo, which actually hails from Sichuan in China and has been recorded as being “root hardy” to as low as -20C if kept dry. So even when the above-ground section of the plant is turned to mush by freezing temperatures below -5C, it is capable of regenerating from energy stores in underground corms the following spring.
Planting young plants on a 20cm-thick layer of gravel or pebbles will help ensure the corms they later develop do not sit in sogginess when dormant over winter, as the bacterial and fungal infections this can trigger can be more damaging than the cold. A 10-15cm layer of mulch, such as chipped bark, will provide an insulating blanket to keep out the worst of the frost.
One important consideration is rarely mentioned: wind. Growing up to 5m tall with leaves 2m long, the beautiful silhouette of this plant is ruined by winds that tear the leaves to ribbons. Bananas work best in urban courtyards, woodland planting schemes and walled gardens – anywhere protected from strong gusts.
M sikkimensis is from the chilly highlands of north-east India, has an allegedly similar level of hardiness to M basjoo (although in my experience it is a touch more tender), and looks even more exotic, with bright burgundy splodges across its glossy olive leaves. As they are grown from seeds, not cloned like M basjoo, there is a great deal more genetic variation in this species, with some having far more colourful leaves, for example. This may also explain why hardiness reports vary, so it is worth testing out seed from a range of suppliers to see what you get.
If you are after something smaller, try the closely related Golden Lotus banana, M lasiocarpa. Like other hardy bananas, it hails from high-altitude locations in China, making it as a good third place in terms of hardiness (roots will probably handle lows of -10C for short periods if well mulched). What it lacks in terms of extreme cold tolerance it makes up for in spectacular, canary-yellow flowers in the shape of lotus buds. Growing a maximum of 2m high, with silvery, glaucous leaves, this means in really cold areas they could be lifted and treated as beautiful conservatory specimens in the chilliest parts of the country.
Aside from that, all you really need to do to ensure the best summer display possible is to know that it is essentially impossible to over-water (or over-fertilise) an outdoor banana in full growth. So if you are generous with the watering can, these botanical beauties will return the favour tenfold with some of the most dramatic leaves possible on our chilly island chain.