What size pot, and when do I pot up (or what if she's out of room)?

Pot up when the plant tells you, not when she looks big. Three checks, no tools: the weight, the roots and the droop. Then move up one size, about two fingers of fresh mix all the way around. A pot that's too big too early stays wet around roots that can't reach it yet.

Pick it up. The pot tells you when it's time.

Pot size is a watering decision

A big pot feels generous. For a small plant, it's a sponge that never wrings out. The plant can't drink the water fast enough, so the mix stays wet and the roots run short of air. A pot that's too small has the opposite problem: it can't hold a full day's drink, so she's thirsty by afternoon.

Moving up in steps keeps the mix drying back at a pace the roots can keep up with. A plant that looks too big for its pot is a cue to check, not the answer.

The three checks

1. The weight. Lift the pot right after a full watering. That's your heavy. When it starts going light sooner, watering after watering, in the same room, the roots are catching up to the pot.

2. The roots. White root tips showing at the drain holes are a sign to check. Let it dry back a little, hold the stem between your fingers, tip the pot and ease the ball out. White roots wrapped around the outside and a ball that holds its shape means it's ready.

3. The droop. If she droops sooner than she used to, the pot is light, and she usually perks up 30 minutes to 2 hours after a drink, the pot likely can't hold a full day's drink anymore.

One check that isn't one: droopy with a heavy pot is almost never a pot size problem. Don't water, and don't repot. That's the overwatering pattern, so see our watering page.

How big a step

Set the old root ball inside the new pot and look at the gap. About two fingers of fresh mix all the way around is a good step. Doubling the width feels like a small move, but it's far more than double the soil, and that's the too big pot problem all over again.

Autoflowers run on a clock and lose days to every move, so many growers start them in the final pot.

Moving her

• Water it in until the new mix is wet through. In coco or a soil you feed from bottles, that means 10 to 20% coming out the bottom. In a living soil, skip the runoff.

• A little droop for 1 to 3 days is common, and some plants show none.

• Give it 5 to 10 days before the next big change, like topping or the flip.

When to make the last move

Plan the last move into the final pot so she's settled before you flip her to flower. Count back from the day you plan to flip and give her those 5 to 10 days first. The roots want to settle in before the stretch starts.

Out of room, and late in the grow

If she's already flowering and has outgrown her pot, try not to repot. The move can stall her right when she should be building flowers, and that can cost more than the small pot does. Most growers are better off finishing her where she is:

• Water more often, not more at once. A small pot dries fast, so smaller, more frequent drinks keep her steady.

• Keep the pot out of the heat. A pot on a hot floor or in afternoon sun dries out even faster and runs the roots hot.

• Size up next time, and plan the last move before the flip.

Before you blame the pot, rule out the easy things: watering timing, and a pot that's running hot. If those are right, it may be the pot.

Fabric or plastic?

Fabric breathes and drains, so it dries faster and you water more often. Plastic holds water longer. Pick by how often you can get to the plants. Either way, keep it out of its own runoff: empty the saucer.

What not to do

Don't start a seedling in a huge pot. The mix stays wet around roots that can't reach it.

Don't repot a heavy, droopy plant. Fix the watering first.

Don't move her right before the flip, and avoid moving her in flower.

When it's something else

• A heavy pot and a droopy plant: see How often should I water, and why is she drooping?

• Roots that smell sour, or roots out the top: see Root rot or just overwatered?

• When to flip: see When should I flip to flower?

Keep going

Fabric and plastic pots, sizes and how many fit your space: see our pots and containers shelf guide.

The right pot at the right time, one change at a time. The whole system for a steady grow is written down in the free Stability Playbook. Get the free Stability Playbook

More answers: all grow guides. Every shelf guide and maker feed chart: Grower Resources.