Time to Plant Onions and Garlic

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Onion bulbs ready for harvest

Onions seeded in fall will be ready for harvest next spring.

Onions and garlic have the latest planting date of our hardy vegetables, and also one of the longest maturation times. Onions and garlics planted this fall will be ready to harvest next spring and early summer. Growing these flavorful crops is relatively easy, if you prepare your soil and choose varieties adapted to the south.

Soil Preparation

Onions and garlic need good soil conditions and full sun to grow well. Good drainage is essential. So is a rich, loamy soil with plenty of organic matter. Raised beds are ideal for growing onions and garlic since they provide good drainage and can easily be amended by tilling 2”-3” of compost into the soil.

Onions and garlic grow best when the soil pH ranges from 6.0 to 6.5. If you have acidic soil, you will need to add lime. If you do not know the pH of your soil, submit soil samples to the NC Department of Agriculture for analysis. There is no charge for soil testing if samples are submitted before the lab’s peak season, which begins Nov. 26. and runs through March 30.

Soil test boxes, forms and instructions are available from any Cooperative Extension office. Completed samples can be mailed to the NCDA&CS Soil Test Lab in Raleigh (the address is on the box). Your results will be posted online, usually within two to three weeks of submitting samples. Results from samples submitted in the past 3-4 years are available online. Learn more about soil testing.

Growing Onions

In the southeast, the easiest way to grow onions is from seed planted directly into the garden from mid September through late October. Plant seed 1” apart and ½” deep in well prepared soil. Be sure to keep newly planted seed evenly moist to ensure good germination and growth. As the onions grow, thin out the seedlings so individual plants stand 3” to 4” apart. Onions pulled during thinning can be used as green onions.

The real key to success with onions is to grow varieties suited to our area. Bulb production in onions is heavily influenced by day length. Because of this, onions are separated into long day and short day varieties. Long day varieties are grown in the northern US in the summer, while short day varieties are grown in the southern US through the winter. Short day varieties (also known as Spanish onions) are sweet but do not store well for extended lengths of time.

Favorite short day varieties for our area include Texas Supersweet, a large sweet yellow onion; Grano varieties, available in yellow and red selections; Granex, often grown in Vidalia, GA; and Candy, a white, day neutral variety that can be grown in fall or summer.

Growing Garlic

Garlic is best planted from cloves purchased from garden centers or mail order companies since garlic purchased from grocery stores may have been treated to prevent sprouting. Individual cloves should be planted 1” deep and around 4” apart in well drained, well prepared soil. Both hard neck and soft neck varieties are available. Soft neck varieties are recommended for southern gardens. These varieties have a slightly milder flavor and are good for braiding.

Though not a true garlic, elephant garlic grows well in the south and is cultivated the same as garlic. Elephant garlic looks similar to garlic, except it produces four to six large cloves that have a very mild garlic flavor. Shallots can also be grown in the fall in the south and are planted from bulbs.

More Tips

Onions and garlic don’t compete well with weeds, so keep these crops well weeded. Both require a steady supply of moisture and nutrients, which is best achieved by mixing compost into the soil and applying a slow release or organic fertilizer at planting time and again in the early spring. High soil sulfur levels make onions hotter. Avoid adding sulfur to the soil if you want sweet onions. Products high in sulfur include those sold as soil acidifiers, gypsum (sometimes referred to as land plaster), and fertilizers that contain sulfate (for example, ammonium sulfate and potassium sulfate).

If you’re mainly interested in harvesting green onions (aka scallions) then plant bunching varieties like ‘Evergreen Bunching’ which form plenty of tops but no bulbs. Green onions can be ready for harvest in as little as 30-40 days from seeding. Sow a new batch every few weeks through late October for successive harvest. If you have limited space, consider planting chives, an easy to grow perennial herb related to onions. Chives grow well in containers and their leaves can be harvested from spring through fall. Garlic chives is similar, but has a pronounced garlic flavor.

Learn More!

Use Extension Search to find research based information from Cooperative Extension systems across the U.S.

Visit your local Cooperative Extension office to learn more about gardening and landscape care. Find your county Extension center.

Subscribe to the Chatham Gardener email list to receive timely updates on sustainable lawn, garden, and landscape care for the central NC Piedmont.