Allium cepa (bulbing onion); Allium fistulosum (bunching onion) · Liliaceae (lily family) in SP 103; Alliaceae (Amaryllidaceae) in the commercial handbook
Florida gardeners grow two kinds of onion. Bulbing onions must be short-day varieties, such as the Granex type sold as Vidalia, planted in fall. Green or bunching onions can be planted from fall through spring. The key with bulbing onions is choosing a short-day variety and planting it in fall.1, 2
When to plant onions (bulbing and bunching) in Florida
seed, sets, transplants or division depending on type; sets are quicker and easier than seed for bulbing onions
Seed depth (inches)
¼ to ½ for seed; sets about 1 inch deep
Spacing in the row (inches)
bulbing 4 to 6; bunching 2 (green onions) or 6 to 8 (shallots)
Between rows (inches)
14 (SP 103); Gardening Solutions says a foot between rows of bulbing onions
Days to harvest
bulbing 100 to 130; bunching 50 to 75 for green onions, 75 to 100 for shallots
SP 103 planting dates. Bulbing: north Sept to Dec, central Oct, south Oct. Bunching: north Sept to Mar, central Aug to Mar, south Sept to Mar. Gardening Solutions says to plant bulbing onions Sept through Dec. Set onion sets upright for straight stems. Plant green onions close and pull (thin) them as needed. Divide and replant multiplier types every year.
5.8 to 6.3 (SP 103's general target for vegetable gardens on sandy soil; no change is needed anywhere from 5.5 to 7.0). No crop-specific figure was found.
Water
Water often to keep growth steady.
Fertilizer
A complete balanced fertilizer at planting, then a nitrogen fertilizer monthly.
Well-drained soil high in organic matter. Home-grown onions may not taste like store-bought ones, since flavor depends partly on soil and fertilizer.
Thrips, leafminers, caterpillars (beet armyworm, cutworms): Listed in the onion pest table of the commercial Vegetable Production Handbook (CV299), not a home-garden guide.
Purple blotch, downy mildew, Botrytis leaf blight: Listed among onion diseases in the same commercial handbook.
Bulbing onions are ready in four to five months, typically once about a quarter of the green tops have fallen over. Cure them for a couple of weeks somewhere cool, dark, dry and well ventilated, then trim tops and roots and store in a cool, dry place. Green onions are pulled as needed. Shallots are lifted when the leaves turn brown; keep dry bulbs cool and dry (save some to replant) and eat refrigerated green tops within two weeks.
The FAO manual says root vegetables such as onion should be grown in wicking beds attached to media beds, and rates bulbing plants like onions as having medium to high nutrient demand. It also lists scallions and chives among other crops commonly grown in aquaponics, and SRAC 454 counts chives among the high-value herbs, but neither source gives guidance for bunching onions by that name.
What this lesson doesn't cover yet
No home-garden list of onion pests was found; pests come from the commercial handbook.
Gardening Solutions says shallots are harvested 'in early summer' and also '50-60 days after planting' after a fall planting, which do not agree; neither timing is used here.
SP 103 gives 14 inches between rows; Gardening Solutions says a foot.
No crop-specific soil pH figure was found.
Your county extension office and its Florida Master Gardeners can fill these in for your garden.