I’ve heard ‘plants like being rootbound’ said so often that it feels like it has to be a fact, right? Not at all! Of course plants don’t like being rootbound. Plants outdoors don't have compact little root balls only growing directly underneath them. So why do we do this to them indoors? To save plants from us!
Kept in ‘too big’ a pot the chance of root rot goes WAY up. Lots more substrate means lots more capacity to hold water. Root rot can be a death-sentence. A smaller pot reduces the chances of root rot, protecting plants from over-watering. Under-watering and less substrate is so much safer. Water again too soon, or keep the substrate too moist, and that smaller pot could be a life saver.
Another benefit (for us) is forced reproduction. In response to the stress of being rootbound, plants can divert their energy from growing roots and leaves to survival mode. For some that means flowers, for other’s pups. Flowers make US happy and it’s easy to think flowers mean a happy plant, but they might be super stressed and responding to conditions that tell them they’re going to die.
Limiting space for roots limits growth. Want a bigger plant? Don’t be scared to pot up. BUT - and this is biggie - be extra careful about what you pot into.
The bigger the pot, the more important a free-draining, airy substrate becomes. Typical indoor potting mix holds too much moisture for too long, drowning roots. Buy or DIY a substrate that holds little to no water to make a larger pot safer. I love the Bioleaf potting mix.
You’ll often see advice to pot up 1 to 2 sizes only. For example, from a 14cm wide pot to a 16cm wide pot. Another benefit of not potting up too big is leaf growth. When you jump up too much in pot size, a plant can appear to ‘stop growing’. That’s normal. And it is still growing, but not where you can see it.
Once they recover from repotting, plants given much more room than before will shift growth to below-ground instead. They get busy sending roots out to explore all that new space first, instead of growing leaves. If you do upsize too big too soon, you may have a long time to wait before your plants diverts its energy from the roots back to stems and leaves.
Two other considerations are looks and space. With a jungle my size, huge pots restrict how many plants I can fit. See? All about me again ;) Plus I admit some plants look plain silly in a pot that’s ‘too big’.
If it is time to repot, here's what to do BEFORE you repot >