How to Grow Carrots: Straight, Sweet Roots Every Time

Carrot quick facts

On this page

• Carrot quick facts
• The soil decides everything
• Why do carrots fork and grow crooked?
• Carrot types and varieties
• How to sow carrots step by step
• Why does carrot seed take so long to germinate?
• Zone chart: sowing and harvest for USDA zones 3–6
• Succession sowing for a harvest all season
• Do you have to thin carrots?
• Carrot rust fly: damage, generations and what actually works
• Watering, feeding and weeding
• Splitting, green shoulders and aster yellows
• When and how to harvest carrots
• Storing carrots in sand, in a clamp or in the ground
• Carrots in raised beds and containers
• Common mistakes
• Frequently asked questions

The soil decides everything

A carrot builds a taproot: it drives straight down, then swells sideways. Anything in the way – a stone, a hard clod, a compacted layer – forces it to swerve or split. Soil preparation is not one factor among several. It is the factor.

The right soil and the right depth

The ideal is a sandy loam: light, open, free-draining but able to hold moisture. Light clay works well if properly worked. Heavy clay and stony glacial till produce the most misshapen roots, and the answer there is a raised bed of sieved soil or a short-rooted type.

Loosen to 25–30 cm (10–12 in) for long varieties and pick out any stone bigger than a thumbnail. Rake the surface fine and clod-free — carrot seed cannot push past baked soil. Sieving the top 5 cm (2 in) is worth the twenty minutes it takes.

Organic matter yes, manure no

Carrots are light feeders. Fresh manure causes two problems at once: roots fork when they hit pockets of concentrated nutrients, and the smell draws in carrot rust fly. Feed the previous crop, not the carrots. A bed that grew potatoes last year is a classic choice because the ground is already deeply worked, as the guide on how to grow potatoes explains. If the bed truly needs feeding, use well-rotted compost worked in the previous autumn.

pH and rotation

Carrots prefer pH 6.0 to 7.0, and yields drop below 5.5. Lime in autumn if you need to, never at sowing time.

Do not grow carrots on the same ground more often than every four to five years. Rust fly pupae overwinter in the soil, and last year's bed is where they wake up. The same rule covers every umbellifer: parsnip, celeriac, parsley and dill. Following carrots with alliums works well — see how to grow garlic.

Why do carrots fork and grow crooked?

This is the most asked question in carrot growing, and the answer is almost always mechanical: the root met something it could not get past.

Four of those six are settled before the seed is even in the ground. Carrot growing is ninety per cent preparation.

Two variations: roots as thin as pencils come from sowing too densely, skipping the thinning or too much nitrogen. A row that never came up is nearly always the seedbed drying out.

Carrot types and varieties

Carrots are grouped by root shape, and the shape decides what soil the variety can handle. Fit comes before flavour: on shallow or stony ground, do not try to talk a 25 cm Autumn King into growing straight.

The day counts are guides from sowing to full size, and the seed packet outranks the table — a cold early summer adds two weeks. Baby carrots pull three to four weeks sooner. Coloured varieties such as 'Atomic Red', 'Deep Purple' and 'White Satin' come in most of these shapes.

Varieties with some rust fly resistance

'Flyaway' F1, 'Maestro' F1, 'Resistafly' F1 and 'Sytan' are less attractive to rust fly larvae, though the RHS is clear that this is a difference of degree, not immunity. They are a second line, not a substitute for mesh.

Early carrots or storage carrots?

Early carrots are thin-skinned and juicy but split if left standing. Storage carrots have tougher skin and more dry matter and are bred to sit in damp sand for five months. Sow both.

How to sow carrots step by step

Carrots are always sown where they are to grow. They do not take transplanting — the taproot is damaged and the result forks. That includes the plug plants garden centres sometimes sell.

1. Wait until the soil is workable — it should crumble, not smear, when squeezed. 7 °C (45 °F) at 5 cm (2 in) is the practical floor.
2. Rake the bed fine — an even surface down to at least 5 cm (2 in), no stones or clods.
3. Draw shallow drills 1–2 cm (1/2–3/4 in) deep, 25–30 cm (10–12 in) apart, using a board edge so the depth stays even. Uneven depth gives uneven emergence.
4. Water the drill before you sow. Soak the base and let it drain. The seed then sits against moist soil from the first minute.
5. Sow thinly. One seed per centimetre (two per inch) is plenty, and thinner is better. Mix the seed with dry sand if it is hard to control. Less thinning later means fewer carrot flies.
6. Cover lightly and firm with 1–2 cm of sieved soil, pressed gently with the flat of your hand.
7. Mark the row with radish seed in the same drill — it germinates in four days and shows where the row runs.
8. Cover the bed immediately with insect mesh or fleece over hoops, edges buried all the way round.
9. Keep the surface moist for three weeks, with a light watering every day or two until the seedlings are through.

In zone 6, and sheltered parts of zone 5, you can also sow a Nantes type in November once the soil is too cold for the seed to germinate. It sits over winter, comes up in March and crops two to three weeks earlier than a spring sowing. It needs ground that is not waterlogged, so try a short row first.

Why does carrot seed take so long to germinate?

Carrot seed is small and carries almost no food reserve. It also contains germination-inhibiting oils that water has to leach out before the embryo starts moving, which is why it needs steady moisture rather than one good soaking. The rest is soil temperature — the figures below come from Oregon State University Extension.

Sow into cold April soil and expect three weeks without worrying. Sow in June and the seed is up in a week, but that is when drying out is most likely. Soaking seed for 24 hours shortens things, but it must then go straight into moist soil.

Three habits make the difference: water the drill rather than the bed, lay a board over the row in hot windy weather and lift it at the first green, and break any surface crust with a fork before sowing.

Zone chart: sowing and harvest for USDA zones 3–6

Carrots are hardy in themselves — the tops shrug off light frost and the roots sweeten after a cold snap. Zones say more about how early the ground can be worked and how long the season runs. Treat the chart as a guide: soil temperature matters more than the calendar.

The sowing window shrinks fast going north: zone 6 gives nearly four months, zone 3 barely six weeks. Fleece over hoops effectively moves you one zone south — it lifts soil temperature, slows evaporation and shuts out the rust fly at once.

Succession sowing for a harvest all season

The difference between a bed that feeds you for two weeks and one that feeds you for five months is succession sowing. An early carrot left standing through August heat splits and turns woody, so sow the same bed several times. A plan for zone 5:

1. Early April: a short row of Amsterdam or Nantes type under fleece, for baby carrots from late June.
2. Late April to early May: Nantes type, the main row for summer pulling through July and August.
3. Late May to mid June: a storage variety — Flakkee, Berlicum or Autumn King. The year's most important sowing: lifted in October, stored to March.
4. Late June: one more Nantes row for September and October, which also misses the rust fly's first generation entirely.

Allow three weeks between sowings and stop when there are fewer days to first frost than the variety's growing time plus two weeks. A metre of row gives 1.5–2.5 kg (3–51/2 lb); a household of four needs ten to twelve metres (33–40 ft), at least half storage varieties.

Do you have to thin carrots?

Yes, if you sowed thickly — unthinned carrots come out thin and tangled. But thinning is the riskiest job in the crop: bruised foliage releases a strong scent, and that scent is exactly what female carrot flies navigate by. A freshly thinned bed on a still June evening is an invitation.

1. Thin early, at two true leaves and 4–5 cm (11/2–2 in) tall. At that size you will not disturb the neighbours' roots.
2. Thin in two stages: first to 2–3 cm (1 in), then to 4–6 cm (11/2–21/2 in) once the roots are finger thick. The second batch is worth eating.
3. Snip, do not pull. Cut the tops off at soil level with small scissors. Pulling a plant tears the root hairs of three neighbours and releases far more scent.
4. Thin in the evening or in rain. Carrot fly is most active in still, mild weather in the middle of the day.
5. Water afterwards. It washes the scent compounds down and closes the soil around the roots.
6. Carry the thinnings away from the plot, and put the mesh back at once — not that evening, that hour.

Better still, avoid it altogether: sow one seed every 4–5 cm (11/2–2 in) and no thinning is needed. Seed tape and pelleted seed make that easy.

Carrot rust fly: damage, generations and what actually works

Carrot rust fly, Psila rosae — carrot root fly in Britain — is the main enemy of the crop across the cool-temperate world. The adult is a slim, glossy black fly 4–5 mm long with a reddish-brown head and yellowish legs. It flies low, rarely above 40–50 cm (16–20 in), and finds hosts by scent.

What the damage looks like

The larva is a slender, creamy-yellow legless maggot up to 9 mm (3/8 in) long. It eats winding tunnels through the root, usually in the lower half and close to the surface. The tunnels are rust-brown and packed with the larva's rust-coloured frass — hence the name. The surface splits into ringed rust-brown scars, and secondary fungi and bacteria move in so the root rots in store. Above ground the foliage turns reddish or bronzed at the edges, then yellows and wilts, most obviously in dry weather. A single plant with reddish foliage in an otherwise healthy row is usually the first sign.

The generations

The fly overwinters as a pupa in the soil or a larva in roots left in the ground. Across most of the cool-temperate range there are two generations a year.

In milder regions a third follows in autumn: Oregon State University reports first-generation adults from mid-April into June and a second flight in August and September. Swedish forecasting work puts development from egg laying to third larval instar at roughly 500 degree days above a base of 3 °C (37 °F) — which is why attacks come earlier in warm years and barely register in cold summers.

What actually works

• Insect mesh over the whole bed, around 0.8 mm aperture, on hoops from sowing day, edges buried, lifted only to thin and weed. RHS research found full covering more effective than a vertical barrier.
• Fleece works too early on and adds warmth, but gets close by midsummer. Swap to mesh then.
• Sow late and thinly. A sowing after mid-May almost entirely escapes the first generation, and every thinning is a scent signal.
• Rotate on at least four years, as far from last year's bed as the garden allows.
• Choose an open, windy spot. An exposed bed gets less damage than one behind a hedge.
• No fresh manure — the smell brings females straight in — and clear the bed completely in autumn, since left-over roots are overwintering sites.

Companion planting with onions and roofless vertical barriers both reduce damage a little; neither stops it. Nematodes (Steinernema feltiae in spring, S. carpocapsae in summer) are worth trying where sold. Attacked carrots are edible once you cut away the tunnelled parts, but they will not keep.

Watering, feeding and weeding

Watering

Carrots want steady soil moisture, not a lot of water: about 20–25 mm (1 in) a week including rain. Water thoroughly and less often — shallow watering gives shallow roots.

The critical moment is the switch from dry to wet. A bed that has been dry for three weeks and then takes 30 mm of rain splits overnight. After a drought, start moderately and build up over a few days. Grass clippings between the rows, laid once the plants are 10 cm (4 in) tall, even out the swings.

Feeding

In reasonably fertile soil carrots need no feeding at all. On poor ground a light potassium-leaning feed as the roots swell helps — potassium builds root and flavour, nitrogen builds foliage. Fast-acting nitrogen in spots is the commonest cause of split carrots.

Weeding

A carrot seedling casts no shade for six weeks, so weeds win unless you intervene. Hand weed at the seed-leaf stage while the bed is moist. Couch grass and other perennial weeds must be gone before you sow — a carrot bed cannot be rescued afterwards. After the second thinning a thin mulch of grass clippings between the rows works well, on the same principle set out in the guide to how to grow cucumbers.

Splitting, green shoulders and aster yellows

Carrots that split

Splits happen when the root grows fast after a slow spell — usually heavy rain or watering after drought, or spot doses of fast-acting nitrogen. The fix is steady moisture, a mulch, restrained feeding and lifting early types on time.

Green or purple shoulders

The top of the root greens where light reaches it. No solanine forms as it does in potatoes, so it is harmless, but the taste turns bitter. Draw soil over the row as the roots push up.

Aster yellows and leafhoppers

Tops that yellow and redden, grow stunted and bushy with a mass of hairy side roots on the carrot itself are showing aster yellows, a phytoplasma disease spread by aster leafhoppers. The roots taste bitter and will not keep. There is no cure: pull and destroy infected plants, control broadleaf weeds, and use the same mesh that keeps out the rust fly.

Bolting in the first year

Carrots are biennial and should only flower in their second year. Flowering in the first summer is bolting, caused by cold stress — a long spell below 10 °C (50 °F) after emergence tells the plant it has survived a winter, and the root goes woody. Do not sow too early without cover, and use bolt-resistant varieties early.

When and how to harvest carrots

Carrots can be pulled from the moment they are as thick as a pencil. There is no exact point of ripeness, only a window where the root is at its best.

• Baby carrots: 55–70 days, when the root is 1–1.5 cm (1/2 in) across at the shoulder. The best flavour of the year.
• Summer carrots: 65–85 days. Pull as you need them and eat within a couple of weeks.
• Storage carrots: 100–130 days. Lift as late as you can but before the ground freezes. One or two light frosts first raise the sugar content — the plant converts starch to sugar as antifreeze.

Scrape the soil off one shoulder and judge the width. If it looks right, pull one and taste it. Storage carrots should not stand more than a couple of weeks past full size.

1. Water the bed the day before if the soil is dry — roots snap off in dry ground.
2. Push a fork down about 10 cm (4 in) beside the row and lever gently without turning the soil.
3. Grip the tops close to the soil and pull straight up with a twist.
4. Shake the soil off. Do not wash carrots going into store — the soil film protects against drying and rot.
5. Cut the tops off at once, 1 cm (1/2 in) above the crown, or they draw water out of the root within days.
6. Sort, eating damaged and split roots first, and let the keepers sit somewhere cool for a few hours before boxing.

Storing carrots in sand, in a clamp or in the ground

A good storage carrot stays crisp until March at just above freezing with very high humidity. Humidity is what most people get wrong — dry air in a warm basement turns carrots rubbery in a month.

The sand box, step by step

1. Take a wooden crate or plastic box and drill air holes if the sides are solid.
2. Dampen clean, untreated sand until it holds together when squeezed but does not drip, and put 5 cm (2 in) in the bottom.
3. Lay the carrots in a single layer without letting them touch — contact spreads rot.
4. Cover with 2–3 cm (1 in) of sand and add another layer, finishing with sand on top.
5. Keep the box dark at 0–2 °C (32–36 °F) and check monthly, removing anything soft.

A clamp, and leaving them in the ground

A clamp is the traditional answer if you have no cellar. Pick a well-drained spot where water does not collect, lay straw on the ground, stack the roots in a cone, cover with straw or dry leaves and shovel 15–20 cm (6–8 in) of soil over the top, leaving a small chimney of straw at the apex. If you open a clamp mid-winter, empty it.

In zones 5 and 6 on free-draining ground the roots can also stay in the bed. Cut the tops, cover with 20–30 cm (8–12 in) of straw or leaves and lay cardboard on top so the cover stays put, and mark the row ends so you can find them under snow. The method does badly in years with deep frost and on heavy soil, and voles find the bed sooner or later.

Carrots in raised beds and containers

If you have ever wondered how to grow carrots on heavy or stony ground, the honest answer is a raised bed. You control the soil completely and sidestep the forking problem.

A bed 120 × 80 cm (4 × 21/2 ft) takes four rows at 25 cm (10 in) spacing — nearly five metres (16 ft) of row. Fill with four parts multipurpose compost to one part sand, sieving out anything coarse. That gives 20–25 cm (8–10 in) of depth, enough for Nantes, Chantenay and Danvers but not the longest Flakkee types. A raised bed warms faster in spring and dries out faster too.

For pots, choose Paris Market or an Amsterdam type: at least 20 litres (5 US gal) and 25 cm (10 in) deep, open compost, thin sowing and watering every other day. Insect mesh on a couple of hoops covers a bed or pot easily.

Dill, parsnip and parsley belong to the same family and should not sit alongside — they share the same pests and diseases. The same rotation thinking runs through the guide to how to grow tomatoes.

Common mistakes

• Sowing into stony ground. The cause of almost every forked carrot. Sieve the top 25 cm (10 in) or choose a short type.
• Using fresh manure. Forks the roots and draws in carrot fly. Feed the previous crop instead.
• Letting the seedbed dry out. One dry afternoon during germination can halve emergence.
• Sowing too thickly. Thick sowing means heavy thinning, and thinning means carrot flies.
• Pulling thinnings at midday. Snip the tops instead, in the evening, and water afterwards.
• Putting the mesh on once the tops show. By then the first generation has already been. The mesh goes on the day you sow.
• Watering little and often. Gives shallow roots and the swings that split them.
• Storing washed carrots with the tops on. The tops draw moisture out and washed skin lets rot in.

Frequently asked questions

When should you plant carrots?
Sow as soon as the ground is workable and holds at least 7 °C (45 °F) at 5 cm (2 in) — roughly two to four weeks before your last frost. That means mid-March in zone 6, early April in zone 5, late April in zone 4 and early May in zone 3. Storage carrots go in from late May to late June.

How deep do you plant carrot seeds?
One to two centimetres (1/2–3/4 in), shallower in light sandy soil. Deeper and the small seed cannot push through. Water the base of the drill before sowing, cover thinly with sieved soil and firm gently so the seed makes proper contact. Even sowing depth gives even emergence.

How long do carrot seeds take to germinate?
Ten to twenty-one days, depending on soil temperature. At 10 °C (50 °F) expect about 17 days, at 15 °C (59 °F) about 10 and at 20 °C (68 °F) roughly a week. The soil has to stay evenly moist throughout — carrot seed carries germination-inhibiting oils that must be leached out, and drying out mid-way stops it.

Why are my carrots forked?
The root met an obstruction: most often stones or hard clods, then fresh manure or pockets of concentrated feed, then a compacted pan under the topsoil. Sieve stones out of the top 25 cm (10 in), feed the previous crop, and choose Chantenay or Paris Market types on shallow ground.

Do you have to thin carrots?
Only if you sowed thickly — unthinned carrots come out thin and tangled. Thin in two stages, first to 2–3 cm (1 in) and then to 4–6 cm (11/2–21/2 in), snipping the tops at soil level rather than pulling the seedlings. Sow thinly from the start and you skip thinning, and with it the scent that draws carrot fly.

How do I stop carrot root fly?
Cover the whole bed with insect mesh of about 0.8 mm aperture from sowing day until you lift, edges buried all the way round. Combine it with a four-year rotation, no fresh manure, thin sowing and an open windy site. Sowing after mid-May dodges the first generation, and lifting before late August dodges the second.

How do you store carrots over winter?
Cut the tops 1 cm (1/2 in) above the crown, do not wash them, and sort out anything damaged. Layer the roots in damp sand so they do not touch, and keep the box at 0–2 °C (32–36 °F) with high humidity. Storage varieties keep four to six months. With no cellar, use an outdoor clamp or leave the roots under 20–30 cm (8–12 in) of straw.

Can you grow carrots in containers?
Yes, and it often beats open ground because you control the soil completely. A raised bed gives 20–25 cm (8–10 in) of depth, enough for Nantes, Chantenay and Danvers. For a pot choose Paris Market or an Amsterdam type, at least 20 litres (5 US gal) and 25 cm (10 in) deep. Fill with sieved compost, sow thinly and water every other day.

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