How big should a cannabis clone be before transplanting?
A cannabis clone is ready to transplant when white, healthy root tips are visibly emerging from the bottom of its rooting medium and the clone has produced at least one new internode of top growth. Physical size matters less than these two readiness signals — a 4-inch clone with strong roots and new growth is more transplant-ready than a 6-inch clone whose roots haven't broken through the medium yet.
Shop HLVD-Tested Clones →Why size alone isn't the right metric
Many growers fixate on the visible above-ground portion of the clone, but cannabis is a root-driven plant. Above-ground growth is constrained by what the root system can support. A clone that looks tall but hasn't yet developed roots is stretching for light and burning through the energy reserves stored in its stem — it won't survive a transplant into a larger container because the larger volume of medium will hold too much moisture for the underdeveloped roots to manage. Conversely, a clone that's compact but well-rooted is in active uptake mode and ready to expand.
What healthy root development looks like
Lift the rooting plug or cube gently and look at the bottom. You're looking for at least 3-5 distinct, white root tips clearly extending past the bottom of the medium. The roots should be bright white — not brown, not gray, not slimy. Brown roots indicate either nutrient burn or root rot, both of which need to be addressed before transplant. The plug or cube itself should hold its shape when you handle it; if it crumbles, the clone hasn't established enough to grip the medium.
What new top growth looks like
Look for at least one new node of leaf development above the original cutting. The new leaves will be smaller and lighter green than the leaves that were on the cutting when it was taken — that's a sign the clone is actively photosynthesizing and producing new tissue rather than just maintaining itself. If a clone has rooted but shows no new top growth after 7-10 days post-rooting, it may be locked out of nutrients in its rooting medium, in which case a transplant is overdue rather than premature.
How long the readiness window stays open
Once a clone hits the readiness signals, you have about 5-10 days to transplant before it becomes root-bound and growth stalls. A clone left in its rooting cube past this window can recover after eventual transplant, but will lose 1-2 weeks of growth time as it works through the stress. For commercial setups running tight schedules, a pre-set transplant cycle of 14-18 days post-cutting works well as a default — most clones hit readiness within that window.
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