Plant Leaves Curling Upwards: 7 Possible Reasons and Fixes

Healthy cannabis leaves sit flat and open to the light. When the edges start curling up like a taco, the plant is telling you something in its environment is off. Leave it too long and your yield can suffer. Here are seven common reasons and how to fix each one.

1. Pests

Check for bugs first. Aphids, whiteflies and other sap sucking insects hide on the undersides of leaves and can twist them upward as they feed. Some are tiny, so look closely.

For a natural option, spray the plant with diluted liquid soap and repeat until the pests are gone. For faster results, use a pesticide made for the pest you are dealing with. If the problem is severe, prune the worst areas to remove pests and eggs.

2. Herbicide damage

Weed killer drifting onto your plants can cause badly curled leaves. Aim herbicides only at the weeds. If your plants get hit, rinse them with plenty of water right away and give them a feed so they do not dry out. Cut off any badly damaged parts.

3. Overwatering

Cannabis needs water, but too much can rot the roots, and root trouble can show up as curling leaves. Water only once the top couple of inches of soil have dried out. Use pots with drainage holes, and add gravel at the base when you repot to help water drain.

If leaves curl and the soil stays soaked, lift the plant out and check the roots. Trim away any mushy, brown roots so the rot does not spread. Our guide to overwatering cannabis covers this in more detail.

4. Too much heat

When it gets too hot, plants lose water fast. Curling the leaves up is how they hold on to moisture. Move plants away from heat sources, improve airflow and add a fan to cool the space. Humidity matters too, so see our guide to relative humidity control for cannabis.

5. Viral infection

Viruses are the most serious cause because there is no fix once a plant is infected. If you suspect a virus, move the plant away from the others right away. Check nearby plants and remove any that show the same signs.

6. Too much light

Too much light can make leaves curl and brown. If older leaves are curling and new leaves come in small with brown tips, your light may be too strong or too close. Raise the light or turn the intensity down. Our guide on when to increase light intensity in flowering explains how to find the right level.

7. Nitrogen deficiency

Nitrogen helps plants make chlorophyll. When it runs short, the plant moves nitrogen to new growth and the older leaves near the base can curl up. A nitrogen rich feed sorts it out.

Keep your plants in top shape

Many of these problems are easy to miss until they do real damage, so check your plants often. Keep heat, light and watering close to what cannabis likes, feed the right nutrients and watch for early signs. Strong airflow helps, but too much can cause its own damage, as our guide to cannabis wind burn shows. Starting with quality seeds from Kind Seed Co gives your plants the best base to work from.