Identify a cucumber leaf, and what is wrong with it
Photograph the leaf and get a confirmation of the plant, plus a read on any yellowing, spotting, curling or mottling.
Choose a leaf photo
Drag a photo here, or tap to choose. JPG or PNG. A clear, close shot works best.
Identifying a cucumber leaf
A cucumber leaf is broadly triangular to heart-shaped with three to five shallow lobes, a rough hairy surface, and a slightly toothed edge. It is noticeably less lobed and softer than a pumpkin leaf.
The vine gives you more clues than the leaf. Cucumber tendrils are simple and unbranched, curling in a single spiral. Cucumber stems are ridged and angular, almost square in places, and covered in stiff hairs. Pumpkin, zucchini and melon tendrils all branch and fork.
The leaves are also arranged alternately along the vine, and the plant climbs rather than forming a bush unless it has been specifically bred to.
Telling it apart from the other cucurbits
| Plant | Leaf shape | Surface | Tendril |
|---|---|---|---|
| Cucumber | Triangular, 3-5 shallow lobes | Rough and hairy | Simple, unbranched |
| Zucchini | Deeply lobed, sharp points | Stiff and scratchy | Branched |
| Pumpkin | Deeply lobed, star-like | Stiff, hairy, coarse | Branched |
| Rockmelon | Round to heart-shaped, barely lobed | Soft, slightly fuzzy | Branched |
| Watermelon | Deeply lobed, grey-green | Softly hairy | Branched |
| Bitter melon | Deeply cut, almost fern-like | Thin and hairy | Simple |
| Fat hen (weed) | Soft grey-green oval | Smooth, mealy | None, does not climb |
What is actually wrong with it
| Symptom | Most likely cause | The fix |
|---|---|---|
| Yellow between the veins, veins stay green | Magnesium deficiency | Epsom salts in a watering can, and check the feed |
| White powdery coating on top | Powdery mildew | Improve airflow, remove affected leaves, milk spray or fungicide |
| Angular yellow patches on top, grey growth beneath | Downy mildew | Remove affected leaves, improve airflow, treat early or pull the plant |
| Fine pale stippling, webbing in the joints | Spider mite | Increase humidity, spray the undersides with water, remove badly affected leaves |
| Scorched or cupped leaf edges | Heat, wind or inconsistent watering | Shade and steady watering. Not a disease |
| Mottled, puckered, distorted new growth | Virus, often cucumber mosaic | No cure. Remove the plant so it does not spread |
| Large holes in the leaf | Caterpillar or slug damage | Check at night, pick off by hand |
The three I get asked about most
Yellowing between the veins. This is magnesium deficiency, and it is by far the most common cucumber complaint. It starts on the older leaves at the bottom of the vine, and the veins stay green while the tissue between them goes yellow. It is not a disease and it will not spread to a neighbouring plant. Epsom salts dissolved in water and watered around the roots fixes it within a fortnight.
White powder on the leaves. Powdery mildew, and cucumbers are especially prone to it. It thrives when the air is still and the days are warm. Thin the vine so air moves through it, water at the roots rather than over the leaves, and remove the worst leaves. A diluted milk spray helps if you catch it early. Once it covers most of the plant, it is usually finished.
Mottled, puckered, distorted leaves. This is almost always a virus, and there is no treatment. Cucumber mosaic virus is spread by aphids and it will move to your other cucurbits. Remove the plant and bin it. Do not compost it.
The things that stop most of it happening
- Water at the roots, never over the leaves. Wet leaves are how most fungal problems start.
- Space the vines out and train them up. Airflow prevents mildew better than any spray.
- Feed regularly and evenly. Magnesium deficiency is usually a feeding problem, not a soil problem.
- Mulch to keep the moisture steady. Cucumbers sulk when the soil dries out and then floods.
- Check the leaf undersides weekly. Spider mite and aphids live there, and you will catch them before the damage shows.
- Do not grow cucumbers in the same spot year after year. Rotate the cucurbits through the patch.
My first cucumber crop failed and I was convinced it was a disease. I sprayed it twice. It was magnesium deficiency, and it would have been fixed by a spoonful of Epsom salts in a watering can.
Cucumber leaves go wrong constantly, and the causes are almost never what people assume. Yellowing between the veins, white powder, angular yellow patches, fine pale stippling — each one has a different cause and a different fix, and spraying for the wrong one wastes money and kills the insects that were helping.
So this page does two things: confirm the leaf is a cucumber, then work out what is actually wrong with it.
Frequently Asked Questions
Broadly triangular to heart-shaped, with three to five shallow lobes, a rough hairy surface and slightly toothed edges. The vine has simple unbranched tendrils and ridged, hairy stems that are almost square in places.