A veggie garden standard, highly nutritious, delicious to eat: how can you go wrong with carrots?
Preparation: Carrots need deep, loose soil - at least 8” (20cm) with plenty of organic matter, and a good mix of sand for drainage, here on the Wet Coast. Be careful, though: if you want to use manure for some of the organic matter, allow at least 8 weeks between the manure application and planting, as too rich a manure mix will lead to many more forked roots. As well, too high a nitrogen content in general (too much manure, compost or nitrogen fertilizer) can lead to hairy, divided roots. Try adding wood ash to the soil: it provides easily-accessed potassium for strong, sweet carrots.
Planting: Carrots are usually direct-sown once the soil is warm enough for germination - in the Vancouver area, as early as the end of March-early April. You can do successive plantings every 3 weeks or so to maintain a steady harvest over the season. Consider planting as late as mid-July for harvest, as needed, into November.
The seeds should be sown about 1/4” (0.5 cm) deep, in rows about 6” (15 cm) apart - or scattered thinly over the bed for a less regimented look. Try to keep the seeds at least 1/2” (1 cm) apart so that thinning doesn’t disturb nearby seedlings. Cover the seeds with very fine soil.
Carrots are slow to germinate, and the soil needs to be kept evenly moist during this time. We cover newly planted carrot beds with Remay (that very lightweight, white fabricky material you can buy in rolls at better gardening stores), either right on the ground with stone weights at the corners, or installed over hoops 12-18” (30-45cm) high. The fabric helps to keep the moisture even, while letting in both rain and light. It also helps keep pests like carrot flies (see below) out of the crop. If you’ve lain the Remay directly on the soil, remove it once the seedlings are 1/2-1” (1-2 cm) tall. Or if the material is over hoops, leave it on for the season.
An alternative to laying Remay on the ground is to mulch the seed bed with straw and allow the seedlings to work their way up through (i.e: don’t bother removing the straw once the carrots sprout). This is somewhat less effective in reducing carrot flies, but is a fully organic option which will provide further organic matter for the soil.
Thinning: Eat while you thin! To maximize the overall harvest, we do multiple thinnings over the growing season, so that we can eat the baby carrots we are pulling. An initial thinning may be needed to achieve the 1/2-1” (1-2 cm) spacing, but then wait a month or more before thinning again, whether all at once or slowly over a number of weeks whenever you need a few baby carrots for the kitchen.
Warning, though: our repeated-weeding method does have the drawback that any kind of bruising of the foliage can draw carrot flies, who are attracted to the scent. Consider doing your weeding on a calm, dry evening when the scent won’t spread much and the insects aren’t flying.
Pests: For whatever reason, we don’t seem to have much problem with carrot flies ourselves, but these are the primary carrot pests that most people struggle with. You often don't know you have a problem until you pull up a carrot and find it has a darkened root tip - and if you look closely, little tunnels bored through the root.
This damage is done by the carrot fly larvae in the soil - but the best prevention works above ground: the floating row covers really help to keep out the flying adults - as does a plastic fence-like surround at least 18” (45 cm) high, which presents a barrier to the low-flying insects. Interplanting carrots with highly scented and insect-repelling garlic, marigolds or pennyroyal may also help.
As with every crop, always rotate your planting locations from bed to bed over a 3-4 year cycle. And finally, to combat carrot fly larvae in the soil, beneficial nematodes will attack the grubs. They will also work against wireworms - another soil grub that burrows into carrot roots.