CORVALLIS - Carrots can still be planted into July for fall and winter harvest in most areas of the state. In higher elevation areas in July, plant only shorter season varieties with 50 to 60 days to maturity. Most seed packets list days-to-maturity information.
From tiny top-shaped Thumbelinas to longer, broad-shouldered Chantenay varieties, carrots keep well in the soil until harvested and eaten.
Beta-carotene gives carrots their orange color, explained Jim Myers, Oregon State University vegetable breeder. Some varieties such as "Healthmaster" are bred to have higher levels of beta-carotene than most other carrots. Red-colored carrots such as Japanese Kuroda carrots and "Nutri-red" contain lycopene, with high anti-oxidant potential.
Carrots grow best in deep, well-drained sandy or peaty soils. Raised beds, worked to a depth of 12 to 15 inches provide optimum drainage and allow for maximum root length and smoothness. Hard soil clods, uncomposted manure or fertilizer granules may cause carrots to fork, become hairy and crooked. A soil pH of 6.0 to 7.0 is optimal.
Sprinkle seed thinly in furrows a half-inch deep, with rows 12 inches apart. Cover lightly with soil. Keep moist until germination. Carrot seed is slow to germinate, often taking 12 to 14 days to sprout. If you want large carrots, thin carrot seedlings to two inches apart after the tops are three inches tall.
For summer-planted carrots, try covering seed with finely sifted vermiculite or compost instead of soil to keep the seed damp until germination and to keep the soil from crusting over.
As summer-planted carrots grow and mature into the autumn, cover the roots with a thick, loose mulch such as straw if the weather gets below 32 degrees. Mulching prevents the tops of the roots from turning green in the sun and keeps them from freezing during cold weather.
Home gardeners are lucky - the varieties of carrots available for planting at home can be much more flavorful and colorful than those commonly found in grocery stores, which are bred to machine harvest, ship and store well. The major types of carrots available to home gardeners include:
- Paris market - round to top-shaped roots, averaging two to three inches in diameter. Good in shallow soils. Varieties include Thumbelina, Planet and Parmex.
- Amsterdam forcing - roots are small to medium in size, slender, blunt tipped. A food choice to grow for "baby" carrots. Varieties include Caramba and Minicore, a 55-day carrot.
- Nantes - medium size, with cylindrical root, blunt tip and smooth thin skins. Roots are sweet and tender. Varieties include Nantes Scarlet, Nantes Coreless, Touchon and Merida, an overwintering variety that could be planted in September or October for spring harvest. Merida is available from Territorial Seed Company P.O. Box 157, Cottage Grove, OR 97424.
- Chantenay - Medium size with stocky, tapered roots. Good for heavier soils. Varieties include Royal Chantenay and Red Core Chantenay and the 55-day Kinko.