As a child growing up in the tropics I used to envy British gardeners. They got to grow all the amazing temperate plants outside that were impossible to keep happy in the relentless equatorial heat. They would also grow species indoors from the world’s rainforests, giving them the best of both worlds. Thirty years later, my opinion hasn’t really changed, but there is something odd about this indoor/outdoor divide. Many plants sold in the UK as houseplants are happier outside.
This is partly due to our perception of the plants’ “exoticness”. When camellias first arrived on these shores, British aristocrats constructed elaborate glasshouses to grow them, assuming their Far Eastern origins must also make them vulnerable to frost. It was only when some of these glasshouses fell into disrepair and the plants still thrived, that they realised the error of their ways.
The same reasoning may explain why wonderfully weird carnivorous species such as Sarracenia pitcher plants and Venus flytraps are still sold in the houseplant section of garden centres. Despite their otherworldly appearance, these species hail not from the tropics, but from the bogs of North America and require a cool, dark period of winter hibernation to keep healthy, They can easily handle lows of -15C. Without this, they lose vigour, not to mention the fact that the extra light and humidity they get out of doors will give them a boost. So for best results plant them by the margins of an outdoor pond or in large, water-filled dishes with no drainage holes.
It’s the same with bonsai, where you will find a jumble of temperate and tropical tree species populating the houseplant shelves. Japanese maples, pines and elms are extremely unlikely to get the light they need indoors, and will start to show it within just a month or two, and without a cool rest in winter rarely survive at all. If you do want an indoor bonsai, pick a Ficus or a Podocarpus (confusingly sold as “Buddha Pines”, even though they aren’t pines) and you will be fine.
Social media can sow confusion, too. When a leading influencer posted about olive trees in her living room, garden centres reported an uptick in demand for these as indoor plants. Unless you have a high-ceiling glasshouse that’s kept cool in the winter, with fans and vents for lots of air flow, olive trees are best kept outside. Most living rooms have the low light and winter warmth that far more closely mimics tropical rainforest floors than the scorching summer sun and cool winters these Mediterranean species need.
The same goes for most temperate species. Many “houseplants” of temperate origin that are notorious for being tricky to grow indoors can be suddenly rendered relatively trouble-free just by sticking them outside. Not a bad deal, really.
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