The two stages every cucurbit seedling goes through
Cotyledons come first. In this family they are thick, fleshy and rounded, sometimes with a slight notch, and they are almost identical whether you planted cucumber, zucchini or melon. If the photo shows only these, the seedling is not yet identifiable.
True leaves come second and carry the real shape of the plant. The first true leaf is the one to photograph. By the second or third true leaf, most cucurbits can be named with reasonable confidence.
The features that identify a cucumber
- First true leaf — three distinct lobes with pointed tips, deeply cut rather than gently wavy.
- Leaf surface — noticeably rough and hairy, more so than melon.
- Stem — angular rather than round, covered in stiff white hairs.
- Tendril — a thin curling tendril appears very early, often by the second or third leaf.
- Growth — fast and vining, reaching for something to climb almost immediately.
- Smell — a crushed leaf smells distinctly of cucumber.
Cucurbit seedlings compared
| Seedling | Cotyledons | First true leaf | Stem | Other clue |
|---|---|---|---|---|
| Cucumber | Thick, rounded, smooth | Three pointed lobes, rough | Angular, stiffly hairy | Tendril appears very early |
| Zucchini | Large, thick, rounded | Broad, shallow lobes, bristly | Thick, brittle, very bristly | Grows fastest of the group |
| Melon | Thick, rounded, smooth | Rounder, smoother, less lobed | Slender, less hairy | Leaf feels softer and less rough |
| Pumpkin | Large, thick, rounded | Broad with wavy edges | Thick and hollow | Very large cotyledons |
| Watermelon | Thick, rounded, smooth | Deeply lobed, smooth | Slender and hairy | Leaves much smoother than cucumber |
| Bitter melon | Thick, rounded | Deeply lobed, smooth-edged | Thin and climbing | Very fast tendril growth |
Photographing a cucurbit seedling
- Photograph the whole seedling from the side so the cotyledons, the true leaves and the stem are all visible.
- Take a close-up of a single true leaf, flat, so the lobing and the leaf edge are clear.
- Show the stem near the soil. The hairs and the angular shape are useful and easy to miss.
- Look for a tendril and include it if there is one. It is a strong clue that the plant is a climbing cucurbit.
- Crush one leaf and note the smell in the context box. Cucumber is unmistakable.
The bitterness warning
Cucumbers, like all cucurbits, can produce cucurbitacin, the compound that makes a fruit bitter and can cause stomach cramps at high levels. A seedling that tastes intensely bitter is a warning sign.
This is not a reason to taste seedlings. If a mature cucumber from your plant tastes bitter, throw the fruit away and do not save seed from that vine. The bitterness is a genetic trait and it will come back next year.
Cucumber, zucchini, melon, pumpkin and watermelon are all in the same family, and their seedlings look almost identical for the first week or two. They all push up two thick, fleshy, rounded cotyledons that give away nothing about which one you planted.
The identification starts with the first true leaf. From that point the family separates fairly quickly, and cucumber has one of the more distinctive first leaves in the group.
Frequently Asked Questions
Look at the first true leaf. Cucumber has three deeply cut lobes with pointed tips and a rough surface. Zucchini leaves are broader with shallower lobes and a bristly texture. Cucumber also produces a tendril much earlier.