Stretched, thin plant with long gaps between nodes

Likely causes, most likely first

Ranked for this sign on its own. Your stage, medium and readings change the order, so run the checker for your plant.

1. PossibleNormal stretch after the flip

   Normal ageingLow urgencyRead: Stretchy, leggy cannabis: a differential

   Fix: Most cultivars grow 1.5-3x in the first 2-3 weeks after the flip. Plan height before the flip; supercrop or LST through it.

   Recovery: Stretch stops by about weeks 3-4 of flower.

   How to confirm it

   • Measure PPFD at the canopy top. Use a quantum (PAR) meter, or a calibrated phone app as a rough guide, at the top leaves in a 5-9 point grid. Compare with the stage target: seedlings 100-300, veg 300-700, flower 800-1,200 µmol/m²/s at ambient CO2. Bleaching and taco at the top above ~1,100 point to light; stretch below ~300 in veg points to too little.

2. PossibleNot enough light

   LightLow urgencyRead: Stretchy, leggy cannabis: a differential

   Fix: Bring PPFD to stage targets: seedlings 100-300, veg 300-700, flower 800-1,200 µmol/m²/s. Yield rose linearly with PPFD from 120 to 1,800 in a controlled trial. Lower canopy buds under ~300-400 µmol/m²/s make larf: thin or lollipop the shaded bottom, or train flat.

   Recovery: New internodes shorten within a week; denser buds on the following weeks of growth.

   How to confirm it

   • Measure PPFD at the canopy top. Use a quantum (PAR) meter, or a calibrated phone app as a rough guide, at the top leaves in a 5-9 point grid. Compare with the stage target: seedlings 100-300, veg 300-700, flower 800-1,200 µmol/m²/s at ambient CO2. Bleaching and taco at the top above ~1,100 point to light; stretch below ~300 in veg points to too little.

Look for

Whole-plant photo with a ruler and the light distance; internode length visible..