Tropical plants in Europe don’t need ice cubes – whatever social media might say

About 10 years ago, I went to a truly amazing horticultural show just outside Amsterdam. It was an exhibition by the very best houseplant growers of their newest creations all displayed on ultra-glossy stands. Right at the centre of the event space was what looked like an enormous music video set with theatrically oversized 1950s-style fridges on podiums. Between these were huge faux ice sculptures, and metre-high martini glasses filled to the brim with plastic ice cubes, all in Miami Vice lighting in shades of pink and blue. You might wonder what this all had to do with horticulture, until I explain that pouring out of all these props were the most immaculate Phalaenopsis orchids with a giant neon sign saying: “Just add ice”. The idea was that the easiest way to water orchids is to simply add three ice cubes to their pot once a week and presumably, by extension, demonstrating how simple these plants were to care for.

More than a decade later, the message of this campaign still echoes over social media, magazines and in overheard conversations at garden centres. But where does the idea that tropical plants should be watered with ice come from?

Perhaps surprisingly, this is a traditional horticultural technique that goes back years before this particular marketing campaign, and at least back to 1980s Singapore where my grandmother taught it to me. But this wasn’t a method of ensuring a slow drip feed of a measured amount of moisture. It was more about the cooling effect of ice on the plant. It was used to coax plants from the tropical highlands, who crave a fresh, spring-like climate, to somehow be happy in the sweltering heat of the lowlands.

Phalaenopsis orchids at the time, alongside azaleas and some unusual begonias, were exotic new introductions to lowland horticulture and, frankly, the only way to keep them happy – prior to the advent of chilled glasshouses – was to cool their root systems with daily applications of ice. As so much of Phalaenopsis culture made its way to Holland via southeast Asia, I can only imagine this would be the most logical origin, with Dutch growers learning of the technique, but not the reason why.

Yet what makes perfect sense in the stifling 32C heat of Singapore is not directly transferable to the 18C of the European living room, which is ironically already at the perfect temperature to mimic tropical highlands. Despite the fact that a small, short-term study at the University of Ohio found the ice to have no adverse effect on orchid flowering at all, I can’t imagine that the chilling effect is beneficial, especially over the long term. Even if it were, is constantly making and doling out ice for your orchids much easier then pouring on a splash of water once a week? I am not sure. Moral of the story… If you find this tip works for you, by all means carry on, but please don’t feel like it’s something you have to do.

Follow James on Twitter @Botanygeek