One of the most wonderful (and peculiar) things about gardening is the seemingly universal desire to defy climate to create landscapes that would be impossible in nature. While Singaporean gardeners flock to see cherry blossom trees flown in from the temperate regions of China and held in chilled glasshouses each “spring”, here in Blighty many of us pay absolute fortunes for exotic palms, which Singaporeans would wander past without a second look. Yet perhaps the most fascinating thing to me are the plants that we seem convinced are impossible to grow in our climate because of their “exotic” appearance when, in fact, they are really quite resilient.
A classic example is the Tasmanian tree fern, Dicksonia antarctica. These pricey specimens look so jungly that it is, indeed, hard to believe they could ever grow on our blustery north Atlantic islands. However, in their native habitat they experience winter temperatures that are largely comparable to the UK, and can often be even lower. Nine times out of 10 when I am shown tree ferns that have been proclaimed to be victims of winter cold, they show all the classic signs not of frost damage but severe and prolonged drought stress: thinning trunks, stunted canopies, desiccated growing points. Rainfall in their Tasmanian habitat can be as much as six times that of the levels in, say, southeast England, so without generous watering from gardeners I promise you it’s almost always thirst that spells doom for them, not cold.
At the other end of the spectrum, there are a range of exotic species like cacti and succulents that, despite being incredibly cold-hardy, cannot handle our comparatively higher levels of rainfall. Much like alpine plants, many bunny ear Cacti Opuntia sp regularly experience months in sub-zero temperatures in their native habitat, where any rain falls as snow. Despite having evolved a number of strategies to handle the frost, they are simply not used to their roots sitting in soggy soils during their dormant period, where they can quickly succumb to rot. So in the UK planting these in a really free-draining mix, and preferably in porous pots sited in a rain shadow, is an easy way to grow “impossible” plants surprisingly easily.
There are a huge range of plants we don’t even try to grow due to the assumption that they are not cold-tolerant. Most of us still follow Victorian advice that assumes species like dahlias and even cannas are not hardy, despite the fact that they will happily spring back up from their undergrowth tubers across most of the country even after a particularly cold winter, especially if given an insulating layer of mulch. These misconceptions have only been gradually overturned by horticulturists carefully observing their plants’ behaviour and paying close attention to how conditions affect their growth. So this winter, keep an eye out and you may find you can grow many plants you might have assumed impossible.
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