How to Sow Carrots and Get Them to Germinate Evenly

Germination is half the crop

Germination is the one real obstacle in growing carrots. Get past it and the rest is thinning and drawing soil up around the shoulders. Almost everyone who struggles is not losing plants to pests: they never got half the seed to come up in the first place.

There are only three reasons it fails. The covering is too thick for light to reach the seed, the surface dried out before germination, or the soil was above 95F (35C) or below 50F (10C) and germination stopped. None of them can be fixed after sowing, so decide the date, the covering and the watering before you start.

Decide when you are sowing first, because the same failure has opposite causes in spring and in high summer, and the fix is opposite too.

Carrot seed is short lived and last year's leftovers germinate poorly. Given the cost of resowing, fresh seed every year is the cheaper option.

Spring and summer sowings are hard in different ways

The reliable sowing for a home garden is midsummer for an autumn and winter crop. You sow into the worst of the heat, but after that the temperature only falls, so the roots bulk up in ideal conditions and the flavor is better. A spring sowing has cold soil at germination and the risk of bolting on top of it.

If in doubt, start with the summer sowing. A spring sowing needs a variety specifically selected to resist bolting, or the plant flowers before the root fills.

How to sow

Carrots must be sown where they are to grow. Transplanting damages the taproot and you get forked roots every time, so put the idea of raising them in pots out of your mind. Sow thickly in a drill, let the seedlings support each other, and thin in stages.

1. Draw a shallow flat drill Press the side of a board or a cane into the soil to make a flat-bottomed drill about a third of an inch (1 cm) deep. A level bottom puts every seed at the same depth so they come up together.
2. Sow about half an inch apart Drop seed at roughly half inch (1 cm) intervals. Sowing thickly is deliberate: neighboring seedlings lift the soil for each other and germination improves. Do not overdo it or they stretch.
3. Cover with a quarter inch at most Carrot seed responds to light, so cover it with a quarter of an inch (5 mm), and never more than half an inch. You should just be able to see seed here and there. Deep covering is the biggest single cause of failure.
4. Firm it down Press the covering with your palm or a board. Without contact between seed and soil the water does not reach it, and a thin covering dries fast. Skipping this gives patchy rows.
5. Water gently and thoroughly Water with a fine rose held upwards so you do not wash out the drill. Surface soil washing away leaves seed exposed, and exposed seed dies.

Keeping the surface damp until germination

A quarter inch of covering means the seed sits in the layer that dries first. The whole technique is not letting that quarter inch dry once in the eight to ten days before germination, and forgetting for a single day visibly reduces the number that come up.

1. Lay row cover directly on the bed Put row cover straight onto the soil and weight the edges. The surface dries far more slowly and heavy rain cannot wash the seed out. Take it off as soon as they are through.
2. Or use husks or chopped straw Scatter a thin layer over the surface, thin enough that you can still see soil between it. Piled thickly it blocks the light and slows germination.
3. Water every day Morning and evening in sunny weather, at least once a day. A surface going pale is the first sign of drying. Frequency matters more than volume: you are keeping a quarter inch damp.
4. Break the crust after heavy rain Heavy rain caps the surface and a thin carrot shoot cannot lift through it. If it has set hard, scratch it lightly with a fingertip.

Row cover left on after germination gives you drawn, floppy seedlings. Take it off, or lift it on hoops, once the seed leaves stand up.

Sowing into hot soil

Above 95F (35C) carrot seed barely germinates, and bare soil in high summer reaches 104F (40C) easily. For a summer sowing, how much you can lower the soil temperature is the germination rate. If the forecast shows nights staying above 77F (25C), delaying by several days is a reasonable call.

1. Sow in the evening Avoid the heat of the day: sow in the evening and water well. Water uptake starts overnight as the soil cools, which is more reliable than a morning sowing.
2. Shade the bed on hoops Put shade netting over the bed on hoops to drop the soil temperature several degrees. Laid flat on the soil it traps heat, so it has to be raised. Remove it once they are up.
3. Water the bed the day before Watering thoroughly the day before cools the soil by evaporation and steadies the moisture. Sowing into dry soil and watering only on the day is the version that fails.
4. Leave room to resow Do not sow everything on the first day of the window. Split it in two, a week apart. If heat takes one, the other survives. Summer sowings are at the mercy of the weather.

Avoiding bolting from a spring sowing

Once a carrot has grown to a certain size, a run of cold makes it form a flower bud, and instead of filling out the root the plant runs a flower stem up. That is bolting, and the root is then hard and inedible. Sowing too early in spring is the classic cause.

There are two defenses: variety and warmth. Use a variety sold for spring sowing and described as slow to bolt, then shorten the cold period with a cloche or mulch. Sowing outdoors, it is safer to wait until the soil has genuinely warmed.

1. Check the packet Look for spring sowing and slow bolting on the packet. A variety intended for summer sowing, sown in spring, bolts more often than not even when it germinates.
2. Use a cloche For the earliest sowings a cloche or low tunnel is essential. Ventilate on sunny days, because above 86F (30C) inside the seedlings stretch, so the sides have to be opened and closed.
3. Add black mulch Black plastic on the bed with holes to sow through raises the soil temperature several degrees, so germination is faster and the cold period shorter.

Deciding when to give up and resow

If two weeks after sowing fewer than half are up, make the decision rather than waiting. In cold conditions germination can take three weeks, but in the heat, if nothing has come in ten days it is not going to. Waiting indecisively means missing the resowing window as well.

1. Scattered gaps If only sections of the row are missing, sow again into those sections. They run behind, but at thinning you can even the sizes up.
2. Thin all through Resow the whole bed. Lightly cultivate the surface and redo the covering, the firming and the watering. A summer sowing usually has one more chance in the window.
3. Change one thing Was the covering too thick, did it dry, or was it too hot? Change one condition on the resowing and you will be able to repeat the result next time.

If resowing would push you outside the window, switch to a short rooted variety. A shorter root means fewer days to harvest.