Plant sets of garlic, onions, and shallots early in spring to get large bulbs at harvest. Start these crops indoors where snow or too much rain keeps you out of the garden early in the season.
Garlic, onions, and shallots started indoors give you a head start on the season. Set in the garden as transplants garlic, onions, and shallots will be larger at harvest than those started from cloves, sets, or seeds in the garden.
Here’s how to start garlic, onions, and shallots early:
Step One: Start garlic cloves and onion or shallot sets in compartmented seed starting trays or small pots. Plant cloves and sets indoors as early as 12 to 10 weeks before the last expected frost date. (They can be transplanted into the garden as early as 5 to 4 weeks before the last expected frost.) Remember: garlic, onions, and shallots like to get their start in the cool time of the year and finish in the warm or hot time of the year. If you wait for warm weather before you start garlic, onions, and shallots, you will have small bulbs at harvest time.
Fill trays or pots with a light potting mix or equal parts compost and peat moss. Set garlic cloves or onion or shallot sets into the mix—sow cloves 2 inches deep with the pointed end up; set onion or shallot sets (small bulbs) 1 inch deep.
Step Two: Set pots or trays in a sunny, south-facing window or in the greenhouse or hot house. The soil temperature should be 65°F to 80°F (18-26°C). Keep the soil just moist—not too wet and not dry. After plants sprout, grow them on indoors for about 5 weeks; plants that are 5 weeks old or older can withstand transplanting to the garden before the last frost in spring.
Step Three: Harden off young plants before transplanting by setting them outside in a sheltered spot each day for four or five days. When starts have become accustomed to the weather, transplant them out into the garden 3 to 5 inches apart depending upon the expected size of bulbs at harvest.
Onions and garlic do not like competition from weeds. Interplant onions and garlic with leafy crops such as beets or lettuce; these crops will act as live mulch—their leaves will shade the soil and keep weeds down.
Garlic will be ready for harvest 90 to 100 days after indoor start. Small onions can be harvested from sets in as little as 35 days, 80 days or more for large bulbs. Scallions can be harvest in as few as 35 days after transplanting into the garden.