When to Plant Garlic

The goal: roots before winter, leaves after

Garlic has to spend about two months at 32 to 50°F before it will form a bulb, according to University of Maryland Extension. Fall planting gives it that cold naturally. The clove also needs enough time in cool soil to grow a solid root system, which then drives the burst of leaf growth in spring. Big leaves before bulbing mean big bulbs.

The risk is planting too early. In warm soil, a clove can send up green leaves in fall, and that growth gets damaged in a hard freeze. Wisconsin Extension wants the shoot to grow out of the clove but stay below the soil surface until the first hard freeze. Maryland, with milder winters, is content with a few leaves showing before cold weather sets in. Either way, root growth is the priority.

The dates for your zone above put this window from about the average first frost to two weeks after it.

How extension services time it

Different states describe the same target in different ways:

• Wisconsin: within a week or two after the first killing frost.
• Illinois: 4 to 6 weeks before the ground freezes. NC State gives the same 4 to 6 weeks of rooting time.
• Rhode Island: cloves go in around the average first frost.
• Utah State: mid-September through early November.
• Maryland: mid- to late October.
• Oregon State: September through November.

These rules point to the same place. If your ground freezes long after the first frost, you can use the later part of the window. If it freezes soon after, plant promptly after the first frost.

Regional timing

Cold North (zones 4 to 6). Plant after the first frost, then cover the bed with 3 to 4 inches of clean straw, as Wisconsin recommends. Mulch protects young roots from freeze-thaw swings that can heave cloves out of the ground.

Mid-Atlantic and Northeast with allium leafminer. This invasive fly lays eggs on allium leaves in fall and spring. Penn State advises planting as late as practical so the garlic is only a few inches tall when the fall flight comes through. In southeastern Pennsylvania that means about November 1, and in colder parts of the state about two weeks later than usual. Late planting does not stop the spring generation, so cover the bed with floating row cover in spring.

Humid South. NC State plants from late October through November, extending into December in the southern part of the state, for a May to June harvest. Clemson stresses fall planting in South Carolina, early enough that plants grow plenty of leaves before warm spring days trigger bulbing.

Arid West. Utah State’s mid-September to early November window fits most of the Intermountain West.

Warm-winter areas (zones 9 to 10). The University of Arizona calendar plants cloves in October in the Phoenix area. In Florida, UF/IFAS gives late fall through early winter and recommends softneck Artichoke and Creole types, which need little chill.

If you missed fall: spring planting

Spring-planted garlic usually makes small bulbs because it gets too little cold and too little time to grow leaves before long days trigger bulbing. If you plant in spring anyway:

1. Chill the cloves in the refrigerator for about 8 weeks first, as Illinois Extension advises.
2. Plant as soon as the soil can be worked, which the dates for your zone above put about 4 to 6 weeks before the last frost.
3. Choose softnecks. Wisconsin finds Artichoke types handle spring planting best, and lists ‘Italian Late’ and ‘Silver Rose’ as varieties that can be planted in spring.

Expect smaller bulbs than from a fall planting.

How long until harvest

Fall-planted garlic takes about 250 to 270 days to mature in Maryland, or roughly 5 to 7 months according to the Rhode Island and Arizona calendars. Plantings made in October and November are usually dug from May in the South to July in the North. See when to harvest garlic for the signs to watch for.