If you're like me, your indoor plants probably inspire a mix of joy and guilt.
The guilt is because I feel sure they are root-bound by now — I'm scared to look.
But there is good news. Some of the most popular indoor plants don't require repotting as often as you might think and there are also ways to prolong your green friends' stay in one container.
Terra-Nova Sadowski knows a thing or two about pot plants. She's a senior horticulturist on Gadigal land at the Sydney Botanic Gardens and is responsible for the 18,000-plus potted plants that make up the green wall of their event space known as The Calyx.
At home, she shares her apartment with 40 or 50 of her own.
"My boyfriend jokes that he needs a machete to make it to the kitchen sometimes," she laughs.
Plants that need less repotting
Ms Sadowski says with certain types of indoor plants you can get away with less frequent repotting.
Those include:
- Aroids which include rainforest plants such as philodendrons, monsteras, peace lilies and devil's ivy.
- Alocasias such as elephant ears.
- Epiphytes like orchids.
- Anthuriums including the popular flamingo flowers.
The general rule of thumb for knowing when to repot is to give the plastic container a squeeze to see if it is hard (due to being full of roots) and to check for roots coming out the bottom.
But there are exceptions.
"Just because you have roots coming out of the bottom of a pot doesn't necessarily mean that [plant is] pot bound," Ms Sadowski says.
She explains that in their natural environment monsteras, for example, have roots that stabilise the plant by attaching to trees or logs. So the aerial roots and even those coming out of the bottom of the pot can be quite happy in the air and may just be looking for something to hold on to.
She adds that the roots need air around them so putting them in too much soil with too much watering can kill them faster than not repotting.
"They'd rather be in a very loose chunky mix that's got a lot of air in it and they don't mind having the roots kind of go around and explore the part of the world they're in."
Epiphytes like orchids don't follow the usual repotting rules because they get their nutrients from the air.
"It's very hard for orchids to get pot bound … if you have a clear pot, you might see all the roots really crunched up in the bottom. But because they don't get their nutrients from the soil. It's not that big a deal."
How to know when to repot them
Ms Sadowski says if your plant looks good and you're watering and fertilising it, there's no real need to repot.
But if you notice that it's starting to look unbalanced in terms of the size of the pot compared to the size of the plant, then you might want to step up the size of the pot or reduce the size of your plant.
That will help with stability (so they plant doesn't tip over) and not having to water as much, because a larger plant with less soil will need more regular watering.
Tamara Campbell is a horticulturalist in Naarm/Melbourne who specialises in indoor plants. She says plants like the Zanzibar gem and snake plants, which have rhizomes under the soil will "get to the point where you can no longer keep [them] in their pot".
"Because there are so many rhizomes that … they'll be bursting out of the pot."
She adds it's worth slipping plants like monsteras out of their pots occasionally to check their roots are not circling.
"If they're circling, they can strangle themselves."
"You just … give [the roots] a bit of a prune and pop them back in."
Do you need a bigger pot every time?
One of the annoying things about repotting is that your perfectly sized house plant can suddenly be too big for the spot you have it sitting or the pretty container it's in.
But, if you don't want your plant (or its pot) to get bigger, Ms Sadowski and Ms Campbell agree it doesn't have to.
Ms Sadowski says when repotting plants at The Calyx "a lot of times … we'll just take them out of the pot, root-prune them and put them into the same size pot with fresh soil."
For many plants, she says you can use "the goldfish effect", meaning if you keep them in a small pot they stay small.
"I've got a few [ficus, like fiddle-leaf figs] and I've made the mistake of thinking that they needed a bigger pot, and every time I pot them up they get bigger and bigger and bigger. And now I've got these gigantic plants."
"But what you can do if … that's the size that you want, you can root prune them and pop them back [in the same pot].
"And that's a good way to maintain their size."
Ms Campbell adds you might also need to "do a little bit of pruning on top as well, but plants don't seem to mind that".
For plants that have rhizomes or have multiplied and filled their pot, she adds that you can "divide them up into smaller clumps" and either repot into separate pots or just discard some of them.
Other tips from Ms Campbell to avoid repotting
- Repotting less means it's more important to regularly feed your plants with an appropriate fertiliser.
- If the soil level drops top up with a good quality potting mix, a similar consistency to what is already there.
- For plants with fine roots, regularly squeezing the pot while rotating it and poking into potting mix with a wooden chopstick can help break up the soil and loosen the roots.
