SPANISH ONIONS for fresh market and storage
GREENHOUSE: Spanish onions can be sown indoors any time from early Dec. to Mar. 1st. - for Apr. 20th. -May 1st. transplanting outdoors. Most large seedling growers do the bulk of their seeding in early Feb. Home gardeners should have seed sown by Mar. 1st. Use approx. 1 lb/ 454 g of seed for an acre of transplants. (4,000 seeds per oz/28 g.) Germinate @ 65°F/18°C soil temp. for 7 to 10 days. Direct seed into flats @ 6 to 8 seeds per in/25 mm; about 1/4 in/6 mm deep, cover and firm lightly. After germination, lower air temp. to 60°F/15°C. Thickly seeded rows and high air temps. encourage Damping Off. Use a fungicide every 10 days (Captan). Clip seedlings when they are 5 in/13 cm tall - to 3 in/8 cm to thicken plants. Never use liquid fertilizer on freshly cut tops during sunny periods. Fertilize lightly every 10 - 14 days, to keep plants green. Control thrips with Sevin or Diazinon. Harden plants @ 40 to 45°F/5 - 7°C for 10 days before field transplanting.
TRANSPLANTING: Set plants outside as early as you can get on the land (Apr. 20th to May 1st with us in the north). Make-furrows 1/2 in/13 mm deep, spray furrows with Diazinon or Ethion for onion maggot control. Spread roots out evenly in the furrow, and cover firmly. Space plants 6 in/15 cm apart in rows 12 to 16 in./30 - 40 cm. apart. Cultivate traffic and foot marks before it rains. On sandy soils spanish types can use up to 600 lbs./275 kg of 10 - 20 - 30 fertilizer per acre. Try for a pH of 6.5. Side dress twice with nitrogen, during the season. Keep well watered! Hot onions may be caused by fertilizer imbalance (too acid) The key to sweet onions seems to be, "Grow them fast and keep them growing". When bulbs have reached the size of a coffee cup, bend the leaf stalks over firmly at the neck. This prevents late Aug. rains from causing heart rot, but allows continued growth of the bulb. Pull bulbs in Sept. into wind - rows, dry in the sun for at least 10 days, then store till spring. Outdoor sowings will not mature in the north.