Turnip

Direct sow seed about a half inch deep, roughly an inch apart (3 to 20 seeds per foot of row), in rows 12 to 24 inches apart, as early in spring as the soil can be worked. Sow again every 10 days for a run of harvests rather than one glut. Turnips size up in cool weather and turn pithy and strong-flavored once heat arrives, so a spring crop only finishes well if it is started early enough to beat summer.

Three to four weeks after sowing, sidedress about 1 pound of calcium nitrate (15.5-0-0) per 100 square feet, which is roughly 30 feet of row. Keep the soil pH between 6.0 and 6.5. Turnips need enough nitrogen to build the leaves that feed the root, but too much pushes the plant into top growth at the root's expense and you end up with fine greens and no turnip.

When the seedlings stand about 4 inches tall, thin them to 2 to 4 inches apart in the row. The plants you pull are big enough to eat as greens, so nothing is wasted. A turnip root needs the room to swell, and a crowded stand simply stalls at marble size no matter how well it is fed or watered.

Check the seedlings for small round shot-holes in the leaves. If the damage is heavy on young plants, spray permethrin, which carries a 2-day pre-harvest interval on this crop. Carbaryl also works but its 14-day pre-harvest interval is awkward on a crop you may pull in 40 days. An established plant with a few holes needs nothing. Turnip and mustard leaves lack the waxy coating that protects cabbage and collards, so flea beetles hit them harder, and a seedling can be set back badly before it has the leaf area to outgrow the feeding.

Lay a floating row cover or screen cage over the bed at sowing time, before the adult flies and beetles are active, and seal the edges to the soil. Do not use a row cover over ground that grew an infested brassica crop last year, and rotate to a new bed instead. Cabbage maggot flies lay their eggs at the base of the plant and the larvae tunnel the root, scoring it with grooves that let soft rot organisms in, so a barrier set before egg-laying is the whole control. A cover set over already-infested soil just traps the emerging flies with the crop.

Count back about 10 weeks from your average first fall frost and sow then, which is roughly three to four weeks later than you would sow rutabaga. Sow at the same depth and spacing as the spring crop. The fall crop matures as the weather cools instead of heating up, which is when turnips grow fastest and hold the best texture, and the plants are hardy to fall frosts so the harvest window stays open late.

Give about an inch of water a week from rain or irrigation while the roots are swelling, soaking the soil deeply rather than wetting the surface. Do not let the plants wilt between waterings. Drought stress makes turnips bitter and woody, and a root that grows quickly and without interruption is the one that tastes mild.

Harvest when the roots are about 2 to 3 inches in diameter, which is roughly golf-ball to tennis-ball size. Do not leave a spring crop standing into hot weather waiting for it to get bigger. Store roots and greens separately, and expect only a week or two in the refrigerator. A turnip left too long, or left in the ground through heat, goes pithy and strong-flavored, and the size that looks most impressive is the one that eats worst.