Here’s a Houseplant repotting mistake I see more than almost any other. Someone notices their plant looking a bit tired, decides it must need more space, and moves it into a pot that’s two or three sizes bigger than the one it came out of.

Then they wait...

And the plant sulks...

And they can’t work out why.

The problem is what happens to the soil. When you put a small root ball into a huge pot, most of that pot is now soil with no roots in it. Water goes in, the roots can only drink from their own little patch, and the rest of the soil sits there sodden for days. The roots end up sitting wet, oxygen-starved, and the plant starts to decline. Sometimes it’s quick. Sometimes it takes weeks. Either way it’s frustrating because you thought you were being kind.

There’s a much simpler rule. Pot up by a couple of sizes at most. Match the new pot to the size of the root ball, not the size of the plant above the soil. If a plant has properly outgrown its pot — roots circling the bottom, pushing out through the drainage holes — it wants the next size up. Not the biggest one in the shop.

Inside the repotting module of Houseplant Mastery I walk through the three levels of a rootbound plant so you can tell which stage yours is at, the proper way to ease a stuck plant out without snapping the roots, and an alternative to repotting altogether for plants you don’t want to size up — something called root pruning, which sounds drastic but isn’t.

If you’ve got a plant that’s been sulking since you last repotted it, this is almost certainly what happened. The fix is usually to pot it back down into something smaller and let it recover. Boring advice, but it works.

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​Houseplant Mastery is currently 50% off, doors close Sunday night, and there’s a 7-day money-back guarantee. If you get inside and it’s not for you, just tell me and I’ll refund you. No awkwardness.

Rich