The ideal soil for carrots is light, moist and fertile but without a trace of fresh manure, as this will result in forked roots. However, well-rotted compost can be worked in and Nitrophoska Extra (which recently replaced Nitrophoska Blue) can be added at the rate of about 50g to every metre of row where the carrots are to be sown.
Lumpy, stony soil will also distort the roots, so break up clods and remove as many stones as possible. If this is not feasible, try growing ball varieties.
It takes about 10 days for carrots to come through. One reason they fail to germinate is that they have been sown when the soil is too cold. Below 5degC they struggle, so it pays to wait until the weather warms up a bit.
Alternatively, start small quantities under a cloche and sow more in open ground when it is warmer. Keep sowing every two or three weeks throughout the spring and early summer. Rows can be spaced about 30cm apart so hoeing to keep down weeds is easier, or closer so the foliage blocks light and keeps weeds out.
Sow carrots where they are to grow, as - like their relatives, parsnips - they don't do the transplanting thing. Make a groove about 1.5cm deep and trickle in the seed. Because the seed is fine, some gardeners mix it with sand, and others combine it with radish seed to make sowing easier. The carrot/radish combo is rather hit and miss because it is difficult to get an even mix and pulling the radishes, which mature first, can rip out the little carrots, too. Whichever system you choose, cover seed with about 5mm of soil and press down gently, then water lightly. Keep the soil moist.
As carrots grow, they will need to be thinned. Slim varieties, such as Ladies Finger and Mini Sweet, should be spaced about 1.5-2cm apart, while large-rooted main-crop varieties need 5cm between plants.
Smaller varieties take up to 80 days to mature, larger varieties 90 to 100 days.
If you get tired of the traditional orange carrots, seed is available of white (White Belgian), yellow (Solar Yellow) and purple (Purple Dragon, Purple Haze) varieties.
As with all vegetables, crop rotation is important to prevent disease, so do not grow carrots in the same spot more frequently than once in three years.
Types of carrot
Ball or block: These are useful for stony or rough soil, as they grow only about 5cm long. Varieties include Paris Market and Baby.
Berlicum, chantenay or stump-rooted: Straight with blunt ends, they are of medium length, usually growing about 20cm long. Varieties include Manchester Table, Touchon and Kuroda.
Nantes: Nantes carrots, longer than berlicums, are straight with pointed ends. Varieties include Senior and Topweight.
Carrot fly (Psila rosae), once found only in the Auckland area, has spread to almost every part of New Zealand, including many parts of Otago.
The dark reddish-brown flies, 5mm-8mm long with a wingspan of about 12mm, start appearing in September or October, when eggs are laid in the soil.
The larvae burrow into the carrot, causing massive damage. It is believed carrot flies are drawn by the smell of crushed foliage, so growing strong-smelling crops like onions and garlic between rows of carrots may help.
The organophosphate chemical diazinon controls the pest but gardeners dubious about using it may prefer covering the crop with fine mesh or - because carrot flies are low-flying insects - putting a shield around the crop to help deter them.
Because carrot-fly larvae winter over in parsnips, parsley, turnips, celery and the weed hemlock, not leaving these in the ground over winter is believed to help reduce infestations.
Breeders are trying to produce fly-resistant carrots, so far with limited success.
