Cannabis plant problems
Find what is wrong with your plant by what you see, then fix it. Not sure? Send a photo to the Grow Doctor.
Nutrients
- Nitrogen deficiency: Lower, older leaves turn pale green, then evenly yellow from the tip inwards
- Too much nitrogen (the claw): Leaves are very dark green, almost shiny
- Phosphorus deficiency: Dark, dull or bluish green leaves with brown to purple patches, often on older leaves
- Potassium deficiency: Leaf edges and tips turn yellow, then brown and crispy, starting on older leaves
- Calcium deficiency: Small brown spots with sharp edges on new and middle leaves
- Magnesium deficiency: Yellowing between the veins of older and middle leaves while the veins stay green
- Iron deficiency: The newest leaves turn pale yellow while their veins stay green
- Sulfur deficiency: New leaves turn evenly lime green or yellow, veins included
- Zinc deficiency: New leaves are small, narrow and wrinkled
- Manganese deficiency: Yellowing between veins on new and middle leaves with a thin green border along the veins
- Boron deficiency: Growing tips die back or grow hollow and twisted
- Nutrient burn: Leaf tips turn yellow, then brown and crispy, a few millimetres in
- pH lockout: Several deficiencies at once: yellowing, spots and burnt edges together
Water and roots
- Overwatering: The whole plant droops with leaves that feel firm and swollen, not limp
- Underwatering: Leaves hang limp and soft, like they have no strength
- Root rot: The plant wilts even when the medium is wet
Light, heat and air
- Light burn and light bleaching: The top leaves closest to the light turn yellow or white while their veins stay green
- Heat stress: Leaves fold upwards along the middle like a taco
- Cold stress: Leaves and stems turn purple (beyond what the strain normally shows)
- Air too dry: Leaves curl and feel thin and dry
- Air too humid: Water drops on leaves or walls in the morning
- Foxtailing buds: Small spires of new calyxes stack on top of the buds
- Leggy, stretched seedlings: Long thin stems that fall over
- Wind burn: Leaves near a fan are clawed, dry or torn
- Hermaphrodites and bananas: Yellow banana shaped growths (nanners) appear between the buds
Pests
- Spider mites: Tiny white or yellow dots on the top of leaves
- Thrips: Silvery, shiny scratches on leaves
- Fungus gnats: Small black flies around the soil surface
- Aphids: Clusters of small soft green, black or white insects under leaves and on new shoots
- Whiteflies: Small white flying insects that rise when you touch the plant
- Caterpillars and bud worms: Holes eaten in leaves
- Russet and broad mites: Leaves curl up at the edges and turn shiny, glossy or bronze
- Root aphids: Plants stall and yellow without a clear reason
Diseases
- Powdery mildew: White, flour like patches on the top of leaves
- Bud rot (botrytis): A bud has brown, dry or slimy parts inside
- Septoria leaf spot: Round yellow spots on lower leaves that turn brown with a yellow halo
- Damping off: A seedling suddenly falls over
- Fusarium wilt: Leaves yellow and wilt on one side or one branch first
- Hop latent viroid (HLVd): Plants grow smaller than expected and stay stunted
Handling and timing
- A male plant: Small round balls on short stems where branches meet the main stem
- Transplant shock: The plant droops for a day or two after repotting
- Seeds not sprouting: No taproot after 5 to 7 days
- Stunted autoflower: An autoflower starts flowering while still very small
- Harvested too early or too late: Early: most trichomes are still clear, pistils mostly white, effect thin and racy