Weed leaves curling downwards usually point to overwatering, roots short of oxygen or too much nitrogen; leaves curling upwards like a taco signal heat (often above 28 °C at canopy level) or light that is too intense. Drooping leaves can come from either thirst or overwatering: you tell them apart by lifting the pot and feeling the growing medium. Once the cause is fixed, new leaves grow normally within a few days.
In brief
- Downwards, swollen and firm: too much water or roots without air.
- Very dark green with claw-shaped tips: too much nitrogen.
- Taco-shaped upwards, mostly near the lamp: heat or too much light.
- Limp and drooping with a light pot: thirst; with a heavy pot: too much water.
- Pointing upwards but flat and green: usually a good sign.
Leaves curling downwards
When the leaf bends down from the stem to the tip, there are three common causes.
- Too much water: leaves are swollen and firm, the whole plant looks weighed down, the pot is heavy and the medium is wet a few centimetres down. Wait until the pot feels light and the top 2–3 cm of soil are dry before watering again.
- Roots without air: a pot without holes or with a saucer that is always full, compacted medium, a pot too big for a seedling. Empty the saucer 15–20 minutes after watering and choose media with perlite or fabric pots. In hydroponics, keep the solution between 18 and 22 °C: warmer solution holds less oxygen.
- Too much nitrogen: very dark green, glossy leaves whose tips bend down like a claw. Reduce the feed dose, check the EC and, during flowering, switch to a product with less nitrogen.
How much to water and how often, depending on pot and stage, is explained in the guide to watering cannabis.
Taco-shaped leaves curling upwards: heat and light
If the leaf edges lift and the leaf folds like a taco, the plant is reducing its exposed surface to lose less water. This mostly affects the top leaves nearest the lamp and often comes with dry edges or leaves bleaching in the centre.
| Sign | Likely cause | What to do |
|---|---|---|
| Taco only on leaves near the lamp | light too intense | raise the lamp by 5–10 cm or lower the power by 10–20% |
| Taco across the whole canopy, warm tent | temperature above 28 °C | increase extraction, run the lights at night in the warm months |
| Taco with very dry air | humidity too low for the stage | bring humidity to the values for the stage with a humidifier |
| Taco or crinkled leaves in front of the fan | direct airflow | aim the fan above and between the plants, not at the leaves |
Measure the temperature at canopy height, not on the tent floor: the reference range is 20–28 °C with the lights on. How to cool the tent in summer is covered in the guide to grow tent temperature; distances for each stage are in the guide to LED lamp distance.
Drooping leaves: thirst or too much water?
Leaves that hang without curling are the most ambiguous case, because the same picture can have two opposite causes. The table helps you tell them apart.
| Sign | Thirst | Too much water |
|---|---|---|
| Leaf appearance | limp, thin, wilted | swollen, firm, often curled down |
| Pot weight | light | heavy |
| Growing medium | dry, pulling away from the pot edge | wet even deep down |
| After watering | perk up within a few hours | no improvement or worse |
| Fix | water slowly until a little runs off | do not water until the pot feels light |
Two cases are normal: just after repotting, leaves can droop for a day or two, and some plants lower their leaves slightly soon after the lights go off. If they straighten up on their own, there is nothing to do.
Leaves pointing upwards: when it is a good sign
A healthy plant with enough light and water often holds its leaves raised towards the lamp, with the leaflets fanned open: the so-called 'praying' position. The difference from a taco is the shape: here the leaf stays flat, green and without rolled or dry edges. If praying leaves are also pale or warm to the touch, check the temperature and lamp distance.
Pests and spray damage
Before concluding that it is a climate or water problem, turn a few leaves over and look at them with a loupe.
- Spider mites: pale speckles on the leaf, mites and eggs underneath; leaves crinkle and dry out.
- Aphids: small insects on young leaves and tips, which grow deformed and curled, with sticky residue.
- Thrips: silvery patches and small black dots; affected leaves become misshapen.
- Spray damage: burnt edges and curled leaves after a treatment that was too strong or applied with the lights on. Spray only with the lights off, at the label dose, and test on one plant first.
Against pests, only use plant protection products authorised in Switzerland and follow the label.
Quick checklist
- Lift the pot and push a finger 3–5 cm into the medium: light and dry or heavy and wet?
- Measure temperature and humidity at canopy height with a thermo-hygrometer.
- Check the lamp distance and power setting against the manufacturer's recommendations.
- Measure the pH and EC of the solution with a meter: keep pH at 6.0–7.0 in soil and 5.5–6.5 in coco coir and hydroponics.
- Look at the underside of a few leaves with a loupe, searching for mites and insects.
- Think back to what you changed in the last 3–5 days: feed, spray, repotting, lamp, fan.
- Fix one thing at a time and watch the new leaves: those already damaged will not return to how they were.
If the leaves are also yellowing or getting spots as well as curling, read the guide to yellow cannabis leaves too.
Frequently asked questions
Why are my leaves curling downwards?
Usually because of too much water or too little oxygen at the roots; if the leaves are also very dark green with claw-shaped tips, because of too much nitrogen. Check the pot weight and the feed dose.
Do taco-shaped leaves mean too much heat?
Often, yes: tacoing appears above 28 °C at the canopy, in very dry air or with a lamp that is too close. If only the top leaves are affected, light is the likely cause.
Are the leaves drooping from too much or too little water?
It can be either. A light pot and limp leaves mean thirst; a heavy pot and swollen leaves mean too much water.
Are leaves pointing upwards a good sign?
Yes, if they stay flat, green and without rolled edges: they show a plant with enough light and water. If they are also pale, check the temperature and lamp distance.
Indoor grow lights are in the LED collection.
Updated on 13 October 2026.