Bramble - did you use shop bought compost? I love your idea of using old water bottles (always up for recycling) but thought the compost would be too rich for carrots? (sorry to be so late, just catching up with all the posts on here!). I used a mixture of compost, old soil and new topsoil and had about 50/50 forked and straight but no pests so I'm happy!

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Life may not be the party we hoped for but since we're here we might as well dance