How to grow carrots

A carrot is a taproot, and a taproot records everything it hits. A stone, a clod, a hard pan, a lump of undecomposed compost — each one makes the root fork, kink or stop. This is the single reason most home carrots come out ugly, and it is entirely settled before the seed goes in.

What you want is a deep, open, stone-free bed worked to at least the length of the variety you are growing plus a couple of inches. Sandy loam is ideal and heavy clay is the hard case. Do not answer a stony or shallow bed by digging harder — answer it by changing the variety. A stubby Chantenay or a round Paris Market type will make a good root in ground where a long Imperator has no chance at all, and matching the variety to the soil is the most useful decision in this whole guide.

Two things not to do. Do not add fresh manure — nitrogen-rich, partly rotted material is the classic cause of forked and hairy roots, and it is why the old rotations put carrots in the year after a manured crop rather than the year of it. And do not over-feed generally: high nitrogen buys you enormous ferny tops and a disappointing root underneath.

Carrots are direct-sown and only direct-sown. The taproot is the crop, and disturbing it is the one thing it does not forgive, so every method that involves moving a seedling — modules, plugs, transplanting a thinning to fill a gap — is wasted effort. If you have read otherwise, it was written by somebody who had not tried it.

Sow shallow. A quarter of an inch is plenty, and there is a clear historical trend towards shallower sowing worth knowing about: Burr in 1863 says drills an inch deep, the 1912 table says a half-inch, and current practice is a quarter. All three are describing the same problem from different sides — the seed is tiny and has very little stored energy, and every extra fraction of an inch is more soil for a thread of a seedling to push through.

The seed is slow. Two to three weeks is normal, and cold soil makes it slower still. Sow thinly and resist the urge to compensate for slow germination by sowing thickly, because a thick row is a thinning problem you have created for yourself.

Here is the part almost every short guide skips, and it is the part that actually loses crops. Carrot seed needs the top half-inch of soil to stay damp continuously for the whole two to three weeks it takes to germinate. Not watered daily — damp continuously. Let that top layer dry out once, hard, on a windy afternoon in the middle of the process, and you lose the row. Not some of it. The row.

Worse, a heavy watering or a heavy rain on bare soil can form a crust that a carrot seedling is too weak to break through. So the seedbed has to stay damp without being battered.

The reliable fix is to cover the row. A plank, a length of burlap, a board, cardboard — anything laid directly on the sown row holds moisture and stops crusting. Check under it every day or two from about day ten, and lift it the moment you see the first seedlings, because they will etiolate and die under cover within a couple of days. This is fiddly and it is the difference between a row and no row.

A second old trick that still works: sow a few radish seeds along the row. Radish is up in four days, marks the line so you can weed and water it accurately for the fortnight the carrots are invisible, and is pulled long before it competes.

An unthinned carrot row produces a mat of foliage and a crop of pale threads. Nothing about later care can recover it. Thin in stages rather than all at once, so that losses to slugs or damping-off do not leave gaps: first to about an inch when the seedlings are a couple of inches tall, then progressively, eating the thinnings, to a final spacing appropriate to the variety and how big you want the roots.

The part most guides leave out: crushed carrot foliage smells, and carrot rust fly finds a row by smell from a considerable distance. Thin in the evening rather than the morning, firm the soil back around the plants you keep, water the row afterwards, and take the thinnings away from the bed rather than dropping them between the rows. Every one of those is a small thing and together they are most of the practical defence against the crop's worst pest.

For what the same job looked like when it was somebody's living: the USDA broadcast a radio script on exactly this in 1943, called Thick and Thin. It is in our archive.

Once established, carrots are more drought-tolerant than they look — the taproot is good at finding water, which is exactly why Solomon can grow them through a rainless Oregon summer at a foot apart with no irrigation at all. What they will not take is a drought followed by a soaking. A root that has slowed down and then suddenly gets water expands faster than its own skin can, and splits lengthways.

So the rule is evenness, not volume. If you are watering, water deeply and regularly rather than lightly and erratically. If you are not watering at all, commit to that from the start and space accordingly — the worst outcome is the accidental middle, where a dry August is broken by one enthusiastic hose.

In the maritime Northwest the practical shape of this is that spring-sown carrots need real attention through July and August, and an autumn crop sown in early summer gets the returning rains at roughly the right moment.

Carrot rust fly is the pest that matters. The adult lays at the base of the plant, the larvae tunnel into the root leaving rusty-brown scarring, and by the time you see the damage the crop is what it is. It is a serious problem west of the Cascades and in coastal climates generally.

Three defences actually work. Physical exclusion is the most reliable: floating row cover or fine insect mesh, sealed at the edges from the day of sowing, on ground that did not grow carrots or parsnips last year. A barrier fence of fine mesh two to three feet high also helps, because the fly characteristically flies low. And timing helps — the fly has distinct generations, so sowings placed between them are hit less, though the exact windows are local enough that your county extension service is a better source than any national guide, including this one.

Beyond that: aphids on the foliage in warm spells, generally tolerable; wireworm in ground recently turned from grass, which is a reason not to put your first carrots in a newly broken lawn; and slugs, which take seedlings rather than roots. On the disease side, Alternaria leaf blight in wet seasons, and cavity spot in heavy wet soils — both are much reduced by rotation and by not growing carrots in the same bed two years running.

The wartime guidance on all of this is a good illustration of what has and has not changed. Every mechanical and cultural control the USDA recommended in 1944 is still recommended; almost every chemical it named has since been withdrawn.

Start pulling as soon as roots are worth eating — there is no reason to wait for a size on a packet. Loosen alongside with a fork rather than hauling on the tops, which snap off and leave the root in the ground. If the soil is dry and hard, water the row an hour beforehand and they will come out whole.

Carrots left in the ground through frost get sweeter, and this is real rather than folklore: cold triggers the plant to convert stored starch into sugars, which work as antifreeze in the root. The 1912 manual states the same effect for kale as common knowledge without knowing the mechanism.

In a mild maritime winter you can simply leave the crop in the ground under a deep mulch of straw or leaves and dig as needed, which is the least work and the best eating. Where the ground freezes hard, lift before it does.

Cut the tops off within an hour of lifting. Leaves left on keep drawing moisture out of the root and a bunch left topped overnight is noticeably limper by morning. This is the single most common storage mistake and it costs nothing to avoid.

For keeping: layer the roots in barely damp sand, sawdust or leaves in a box somewhere cold and dark, not touching each other. Just above freezing with high humidity is the target. Burr describes exactly this in 1863 — the finer sorts packed in earth or sand to hold their freshness and flavour — and reckons on them keeping until May or June. That is still about right.

In the fridge, unwashed and in a sealed bag, expect several weeks. Washing before storage cuts that sharply, so wash as you use them.