2017 is the year I have cracked many of the problems of growing carrots.
The crucial issue is sowing into good compost. All my carrots this year were sown in my best compost and the result was too dense a young stand due to the excellent germination rates achieved. Thinning is not ideal for young carrots, but better that than no young plants to grow on into roots.
The featured picture at the top of the post is five rows of Nantes/Sweet Candle sown 2 days before the April Full Moon. 16 weeks after sowing, a test pull suggested roots were ready to start harvesting, providing a steady crop until the end of October.
Two 3 metre rows of Amsterdam Forcing Carrots sown on March 31st were harvested through July (13-17 weeks), mostly finger carrots for salads, but the final harvest on July 27th yielded 3lb suitable for cooking and making soups.
Four 1.5m rows of Autumn King were sown 2 days before the May Full moon, using seeds attached to tape, as sold by Thompson and Morgan. I found laying the tape a bit fiddly, but a good stand has now emerged, as shown below:
Good sized roots already can be discerned when scrabbling the soil around the plants.
I have also experimented growing carrots in 17 litre polypot bags, firstly Sweet Candle for exhibitions (sown 8th April) and secondly, Berlicum as a late crop, sown on 30th June. Germination of both was excellent and the pots are shown below:
The major lesson from 2017 is not to bother sowing carrots in any soil lacking good compost. 2015 and 2016 by comparison gave awful germination without good compost.
So if you are starting out, limit yourself initially to crops which tolerate less rich soil, like broad beans, beetroot, lettuce etc. Once you have mastered making good compost, carrots will grow easily and fresh harvests from the end of June until the first frost in November can be achieved, along with a harvest to store and use through the winter months. But lacking it and the slugs will devour all your seedlings long before you even have decent sized plants.