One piece of houseplant folklore resurfaces from time to time: that we should water our plants with ice cubes.
The Instagram accounts planty hoes and oops_i_wet_my_plants have been facilitating, as one commenter put it, a “comedy horticultural moment” with posts debating the efficacy of watering with ice cubes. In the comments, some followers swear they have a grandmother or old family friend who has successfully been raising orchids using ice cubes for decades.
“[The theory] has been around for at least 10 years from what I can see,” says Tammy Huynh, a horticulturalist from online plant consultancy business Leaf An Impression.
She thinks the current millennial and generation Z embrace of house plants has something to do with its comeback: “People are jumping on the trend now because everybody’s collecting indoor plants and a lot of people have either killed them, or want an easy solution to watering.”
It’s not hard to kill a plant – death by overwatering is particularly common as excess water can pool down the bottom of pots and lead to root rot. Proponents of the cube theory think that ice gives the plant time to slowly absorb water as it melts. It’s not an unsubstantiated idea: in 2017, researchers at Ohio State University studying the use of ice cubes to water orchids found the practice had “no detrimental effects”.
But experts today say it’s not a good approach. “I wouldn’t recommend it,” Lauren Camilleri from Leaf Supply, an online plant delivery business, tells Guardian Australia.
For one thing, the ice cubes could still waterlog your plant if they melt faster than they can be absorbed, she says. But most importantly, the extreme temperature of ice could send your plant into shock – killing it.
“When we bring plants inside, what we’re trying to do is mimic their natural environment as much as possible in terms of light and the way we water them,” she says. “A lot of the plants that do well indoors are tropical plants – they come from the rainforest. So the water they’re getting in nature definitely isn’t going to be overly cold or overly hot.”
Many of the Instagram memes centre around a specific plant: orchids. Are the rules different for them, or are people just looking for an easy solution to caring for a plant that’s notoriously difficult to keep alive?
“Definitely the latter,” says Huynh. “People treat orchids as quite delicate things. But really, all you need to do when you water orchids is put them over the sink, pour water over them until it runs out of the bottom and then let the plant drain completely before putting it back.”
No matter what plant you’re raising, there’s no exact formula for how much and how often it will need to be watered. Your best bet, Huynh says, is to feel the soil and only water once the top few centimetres is completely dry. It’s a little more complicated than just chucking a few ice cubes in the pot, but it works.