Cotyledons versus true leaves
Cotyledons are stored food. They come up first, they are usually simple and rounded, and they sit in a pair opposite each other. They will never grow into anything that looks like the adult leaf.
True leaves come second. They carry the real leaf shape — lobed, serrated, compound, or deeply cut — and they are the leaves you can identify from. If the photo shows only two rounded leaves and nothing else, the honest answer is that the plant is not yet identifiable.
Common vegetable seedlings compared
| Crop | Cotyledons | First true leaves | Other clue |
|---|---|---|---|
| Tomato | Narrow, smooth oval | Deeply toothed, slightly hairy | Strong tomato smell when rubbed |
| Capsicum and chilli | Broad, flat, smooth | Glossy, smooth-edged, no hairs | Dark green, very smooth leaves |
| Broccoli and cabbage | Heart-shaped, notched at the tip | Broad with wavy edges | Purple tinge on stems of red types |
| Carrot | Very fine, grass-like threads | Feathery, deeply divided | Carrot smell on the root |
| Beetroot and silverbeet | Long, narrow, reddish stem | Broad with red or green veins | Deep red stems are the giveaway |
| Lettuce | Small, rounded, pale | Soft, ruffled, no hairs | Milky sap when a leaf is snapped |
| Cucumber, melon and zucchini | Large, thick, fleshy oval | Lobed with a rough texture | Thick, brittle stem with bristles |
| Basil | Small, glossy, rounded | Oval, smooth, opposite pairs | Strong basil aroma |
| Sunflower | Large, thick, paddle-shaped | Coarse, rough, heart-shaped | Very fast growth and stiff stem |
How to photograph a seedling
- Photograph the whole seedling from the side so the stem, the cotyledons and any true leaves are all visible.
- Take a second close-up of a single true leaf, laid flat if you can.
- Show the stem near the soil. Colour, hairs and thickness are useful and easy to miss.
- Include something for scale — a coin or a fingertip works well.
- If the seedling has a smell, crush one leaf and note it in the context box. Aroma settles several families that look alike.
Is it my crop or a weed?
The commonest confusion in a new bed is between a brassica seedling and a brassica weed — both are in the same family and both come up with heart-shaped cotyledons. Shepherds purse, wild radish and hairy bittercress all look like a cabbage at two weeks old.
The practical test is where it is growing. A seedling in a neat row where you sowed is almost certainly the crop. The same plant in the path, or in a clump away from the row, is more likely a weed. Once true leaves open, the leaf edge settles it: most brassica crops have smoother, bluer leaves than their weedy relatives.
When to give up and wait
- Two rounded leaves and no true leaves yet — wait a week and photograph again.
- Fine thread-like seedlings you did not sow, in a mat — likely a grass or a weed, not a crop.
- A seedling that appears far faster than the packet promised — check whether it is a weed before you thin around it.
- A seedling with a milky sap is almost certainly lettuce, chicory or a dandelion relative.
Seedlings are hard to identify because the plant you are looking at is not yet showing the features that define it. The first pair of leaves to appear — the cotyledons — are shaped by the seed, not by the species, so almost every brassica seedling looks the same for a fortnight.
The moment that changes is when the second set of leaves, the true leaves, opens. From that point the plant starts to look like itself. This guide explains the two stages, what to photograph, and how to tell a seedling from the weeds that come up beside it.
Frequently Asked Questions
You are looking at the cotyledons, the first pair of leaves, which are shaped by the seed rather than the species. Almost all brassicas look identical at this stage. Wait for the true leaves to open and the plants will separate.