Carrots are a cool-tolerant root crop direct-sown in succession for a long supply. Danvers is the broad-shouldered, tapered type that pushes through heavier ground better than the slender Nantes, which makes it the carrot for a garden with less than perfect soil. It reaches 6 to 8 inches and stores well.
Carrots want deep, loose, stone-free soil; clay or rocks make the roots fork and stunt. Sow a quarter inch deep every three weeks from a few weeks before last frost into midsummer. Germination is slow, 10 to 20 days, so keep the seed bed constantly moist or lay a board or burlap over it until the sprouts show, then thin to 2 to 3 inches early; crowded carrots stay small. Even water matters most, since a dry spell followed by rain cracks the roots.
Fall carrots harvested after frost are the sweetest, because cold turns stored starch to sugar, and they can be left in the ground under a thick mulch and dug through winter in most zones. The carrot rust fly lays eggs at the base of the plants; a row cover from sowing, or sowing after the first fly generation in early summer, keeps the roots clean. Let a few go to flower in the second year and the umbels feed hoverflies and tiny wasps.
Alternaria blight
Brown circular spots with yellow halos on leaves; spreads rapidly in wet weather.
Remove affected leaves immediately. Water at the base only. A copper-based fungicide can help if caught early.
Aster Yellows
Deformed, greenish flowers, stunted growth, and yellowed foliage. Flower centers may produce tufts of leafy growth instead of normal petals.
No cure. Remove and destroy infected plants immediately to stop spread. Control leafhoppers, which transmit the disease, and remove nearby weed hosts.
Cavity Spot
Sunken, gray-brown elliptical lesions across the root surface, sometimes cracking. Caused by Pythium in wet soils.
Improve drainage and avoid overwatering. Maintain pH near 6.5 and avoid excess potassium. Rotate away from carrots for 3–4 years in affected beds.
Aphids
Aphididae →Clusters of small soft insects on new growth and flower buds.
Knock off with a strong jet of water. Ladybirds and lacewings are natural predators. Insecticidal soap as last resort.
Carrot Rust Fly
Psila rosae →Rust-colored tunnels and brown scarring through the outer root. Foliage may yellow or wilt. Larvae are small white maggots in the root surface.
Cover beds with insect netting at sowing. Delay sowing past the first generation and avoid leaving thinnings in the bed, since their scent attracts flies. Rotate crops yearly.