Sowing carrots: germination and thinning
Learn to sow carrots in a prepared bed, keep the seedbed moist while seeds emerge and thin seedlings without disturbing the roots.
By Marmanda3 min read
Sow carrots directly into their final bed: moving young roots can distort them. In the UK, the RHS recommends sowing mainly from April to early July, with some early varieties started under protection in February or March. Prepare a fine, stone-free seedbed, keep it moist while seedlings emerge, then thin to the spacing given for your crop.
When can carrots be sown outdoors in the UK?
The RHS carrot guide gives April to early July as the main outdoor sowing period. An early variety may be sown under protection in February or March. These are UK reference windows: local soil, exposure and the weather in a particular year still matter. If the ground is cold, sticky or waterlogged, wait until it is workable rather than treating the month as a signal to sow.
Carrots are usually sown where they will grow because disturbing the young root can cause it to fork or become misshapen. Choose a bed that can be loosened and cleared of stones. Break down large clods and level the surface; an even seedbed makes a shallow row easier to water and later thin. The French SNHF sheet also recommends direct sowing, but its March–July dates describe French conditions rather than the UK window above. In other climates, use the packet and local advice to choose a workable sowing window instead of copying UK months.
How deep and far apart should the rows be?
The RHS suggests opening a drill about 1 cm deep, sowing thinly and covering with fine soil. It gives 15–30 cm between rows, depending on variety and available space. Keep the row straight and label the variety so you can distinguish it from weeds. Do not confuse distance between rows with the final distance between roots.
Carrot seed can be slow to appear, as the RHS notes. Keep the surface evenly moist with a fine watering when it begins to dry. A hard jet can wash seed from the drill; standing water is not the goal. Mark the row ends and look closely before deciding that a section has failed, since small seedlings can be easy to miss.
How should seedlings be thinned?
Once seedlings are visible, thin them to around 5–7.5 cm apart, as the RHS recommends. Work gently so roots left in the row are disturbed as little as possible. The RHS also advises insect-proof mesh against carrot fly and avoiding foliage contact while weeding, as the scent can attract the pest; replace the mesh after working. If the soil is dry, water lightly afterwards to settle it. Crowded plants compete for room; leaving every seedling because thinning feels wasteful can produce an uneven row.
The SNHF uses a different French protocol: it thins in two stages, first to 2–3 cm at the two-to-three-leaf stage, then at least 3–4 cm ten to fifteen days later. Its row spacing also varies by short, intermediate or long root shape. Those figures are useful in their own context; do not combine them with the RHS final spacing to make a hybrid rule.
How can you spread the harvest?
Instead of sowing a long row all at once, sow a short row and repeat every three to four weeks while the UK season remains suitable; this is the succession interval suggested by the RHS. Different sowing dates spread the work and can reduce the chance that every row is ready together, though actual harvest depends on variety and conditions.
If emergence is patchy, check whether the surface dried, crusted or was disturbed before resowing. If there are still gaps and the sowing window is open, re-sow only those sections. Record the variety, date and bed so the next sowing can be compared with this one. For wider seasonal planning, see the vegetable sowing and planting calendar; the small-garden guide helps reserve a suitable row.