Cuttings wilting

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. PossibleCuttings losing water faster than they can root

   EnvironmentDeal with it this weekRead: Why are my clones wilting?

   Fix: Keep clones at about 75-90% RH (VPD ~0.4-0.8 kPa), 22-26 °C (72-79 °F), PPFD 100-200 µmol/m²/s; trim large fan leaves by half; vent the dome gradually only once roots show.

   Recovery: Cuttings stand up within 24 h; roots in 7-14 days.

   How to confirm it

   • Check temperature and RH at canopy height with a calibrated sensor. Put a calibrated sensor (salt test: a sealed bag with damp table salt reads 75% RH after 8-12 hours) at canopy height, out of direct light, and log for 24 hours including lights-off. Look for lights-off RH spikes and dew point.
   • 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. PossibleAir too dry / VPD too high

   EnvironmentDeal with it this weekRead: VPD explained: vapour pressure deficit for cannabis growers

   Fix: Raise RH or lower temperature to bring leaf VPD to 0.4-0.8 kPa (clones, seedlings), 0.8-1.2 (veg), 1.0-1.5 (flower). Humidifier, less exhaust when cool, fewer dry hot air inputs. Dry air also speeds spider mites.

   Recovery: Leaves flatten within a day.

   How to confirm it

   • Check temperature and RH at canopy height with a calibrated sensor. Put a calibrated sensor (salt test: a sealed bag with damp table salt reads 75% RH after 8-12 hours) at canopy height, out of direct light, and log for 24 hours including lights-off. Look for lights-off RH spikes and dew point.
   • IR leaf temperature at the canopy top. Point an IR thermometer at the top leaves under the light (5-10 cm away, emissivity 0.95) and at shaded leaves. Leaf temperature above about 30 °C (86 °F) at the top only points to heat or radiant load; leaf VPD can be calculated from leaf temperature and RH.

3. PossibleFungus gnats

   PestLow urgencyRead: Fungus gnats: the watering problem with wings

   Fix: Fix the watering first: let the top 2-3 cm dry. Then Bti drenches (larvicide), Steinernema feltiae nematodes or Stratiolaelaps mites; yellow cards for adults. Larvae chew seedling and clone roots and can open the door to Pythium.

   Recovery: Card catches fall within 2-3 weeks; no larvae under potato slices.

   How to confirm it

   • Sticky cards for 1-2 weeks. Hang yellow cards at canopy height and lay one flat on the medium surface; add blue cards for thrips. Count catches every 3-4 days. Rising counts of small dark flies at the medium mean fungus gnats; slender insects mean thrips; white wedge-shaped fliers mean whiteflies; winged aphids mean a colony nearby.
   • Potato slice test for larvae in the medium. Press 2-3 raw potato slices (1 cm thick) cut side down onto the medium surface. Lift after 2-4 days and look underneath: translucent larvae with shiny black heads are fungus gnat larvae.

4. Less likelyChlorine or chloramine in tap water harming roots and soil life

   Root zoneLow urgencyRead: Water quality for cannabis: RO vs tap, alkalinity, bicarbonates and chloramine

   Fix: Usual tap levels rarely hurt the plant directly; the concern is living soil, beneficial microbes and young roots. Chlorine gasses off in 24 h of aeration; chloramine does not. Remove chloramine with long-contact or catalytic carbon, or about 1 g of ascorbic acid per 100-400 L, or use RO.

   Recovery: Biology recovers over weeks; seedlings resume growth within a week.

   How to confirm it

   • Get a water report (or test your water). Ask your water utility for the annual report or test well water: alkalinity (mg/L CaCO3), pH, EC, Ca, Mg, Na, Cl, B, and whether it uses chlorine or chloramine. Alkalinity above ~100-150 mg/L as CaCO3 pushes root-zone pH up; sodium above ~50 mg/L and chloride above ~70 mg/L are a problem; softened water is high in sodium.

Look for

Wilted cuttings with the dome, plug moisture and any visible root tips in the photo..