Root-Bound Signs: When to Transplant Out of a Solo Cup

Solo cups are perfect for the first week or two — but staying in one too long causes real, avoidable problems.

Once roots hit the cup walls, they start circling instead of growing outward. This stalls growth even if everything above the soil still looks fine — which is exactly why it’s easy to miss until it’s already slowing your plant down.

The clearest sign

Roots visibly poking through the drainage holes at the bottom of the cup. If you’re past day 14-17 and haven’t checked, it’s worth a look before assuming everything’s on track.

What to do about it

• Transplant up, not sideways. A 1-gallon fabric pot is a good next step from a solo cup.
• Then keep sizing up as she grows — roughly 3-gallon after a month or so of growth in the 1-gallon.
• Give her time to settle before flip. A week or two of veg after a transplant lets the roots actually establish in the new space before the stress of flowering starts.

Fabric pots make this whole process more forgiving than plastic — roots that reach the edge get “air-pruned” instead of circling, which buys you a bit more runway if you’re not able to check as often as you’d like.

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