How to Grow Onions

Growing Onions - Online Fact Sheet


Planting Onions


Weed Control

Companion Planting

Pests and pathogens

Varieties of Onions

Harvest & Storage

Canning & Freezing

Onion Recipes



Seed & Nursery Catalogs




Ferry Morse

Park Seed







Companion planting

Garden Pests

How to grow Asparagus

How to grow Blueberries

How to grow Brussel Sprouts

How to grow Cantaloupe

How to grow Carrots

How to grow Cucumbers

How to grow Eggplant

How to grow Peppers

How to grow Potatoes

How to grow Pumpkin

How to grow Raspberries

How to grow Rhubarb

How to grow Strawberries

How to grow Tomatoes

How to Grow Watermelon

Home Hydroponics

Planting Onions

When planting onions choose a garden site that is in full sun and has a well-drained soil. A soil pH of 6.0 to 6.5 is ideal for growing onions. Apply lime and fertilize according to soil test results.

Many gardeners plant onions in a raised bed, rich in well-rotted Compost, manure, and other organic matter.  Manure that contains straw or wood shavings may cause a temporary lack of nitrogen in the soil. The bacteria breaking down organic waste utilizes nitrogen and takes it from the soil. The plants may suffer from this, so add nitrogen fertilizer when digging such manure into the soil.  Onions can be grown from seeds, small dormant onions called "sets," or onion transplants.

Onion Seeds should be sown in the garden in the midfall.

Onion Seedlings however, are easier to grow in a soilless mix under controlled conditions. Sow onion seeds about 1/4 inch deep, covering lightly with a soilless mixture. Most onion seed varieties should germinate in approximately 2 weeks. Grow onions in individual peat pots or cell packs to reduce transplant shock, several plants per cell or pack are advisable.. Onion Seedlings should be grown in a relatively cool location with full sun for optimal results.

Transfer onion transplants into the garden when they reach pencil size in diameter (about 1/4 inch). Set onion plants 1 inch deep, and about 3 to 4 inches apart, After the danger of frost is gone.



Cultivation of Onions

When growing onions keep in mind that they are are shallow rooted and any cultivation should be done carefully to avoid damage to the bulbs or roots. Cultivation should be shallow, without bringing excessive soil to the plants. Many gardeners pull the soil away from plants in order to allow greater bulb expansion. However, this practice is not needed on well prepared, highly organic soil. Mulching can also help control weeds.

Growing Onions in well-drained soils will discourage disease problems. It is always wise to follow a rotation schedule when planting onions.

Watering Onions

Watering is critical when growing onions. Water slowly and deeply to produce healthy onions. Onions should receive about an inch of water per week slightly more in sandy soils. Inexpensive watering timer systems are available .

  •  Excessive watering could easily lead to rot and fungus particularly if your onions are not planted in a sunny area.

Fertilizing Onion Plants

Apply a complete fertilizer such as 8-8-8 or 10-10-10, a few days prior to planting. Onions are heavy nitrogen feeders early when producing roots and top growth. Side dress approximately 5 or 6 weeks after planting with high non sulfur nitrogen fertilizer,  Side dress onions again in late winter. Excessive applications of nitrogen can delay maturity of bulbs, cause thick necks and splitting.

Weed Control

When growing onions keep in mind that they are are the least suited to compete with weeds. Weed pressure can be especially damaging to young onion plants because they are slow growing, have shallow roots and do not have enough foliage to adequately shade the ground. Herbicides are not recommended , as many attack the crop as well... careful/ shallow cultivation and weeding is essential .


Companion Planting

Good Neighbors of Onions are Beets, Cabbage, Carrots, Celery, Cucumber, Lettuce, Pepper, Squash, Strawberries, and Tomato . Bad Neighbors include Bush Beans, Pole Beans, Peas.

Do not plant onions or other members of the Amaryllidaceae family in the same soil for more than one season.. Rotate the crops to various sections of your garden space from season to season.

Planting Chamomile with onions. Improves growth and flavor

See Companion Planting for more extensive information


General Categories of Onions

Bulb-forming onions produce a single bulb in a season. Bulb-forming onions include storage onions and fresh onions. The primary difference between storage and fresh onions is that storage onions keep for a longer period of time.  Storage onions generally have a darker color, thicker skins, and a more pungent flavor than fresh onions. Storage onions can be grown from seed, onion sets, or transplants

Perennial onions, produce clusters of small onions. Perennial onions include potato onions, bunching onions, Egyptian onions, and shallots. Fresh onions don't keep well and are best eaten soon after they are harvested. They are commonly referred to as sweet onions.

For growers purposes Onions can be further divided into Short, Medium and Long day varieties


Short Day Varieties

Yellow Granex A/K/A Vidalia, Maui, Noonday
Sweet ..Made famous by the onion-growing area in and around Vidalia, Georgia. Earliest-maturing variety available, and is recommended for southern growers. Does not store well.

Candy Hybrid Onion
This variety has the same characteristics as the yellow variety, but with a pearly-white flesh. grows just about anywhere in the contiguous U.S.

Onion Red Baron Hybrid
Red "Hamburger" is popular for size and sweetness. Chunks up into big, solid slices up to 4 in. across. Most flavorful used raw. Disease resistant , Stores well


Medium Day Varieties

Organic Falltime Leek 340 Seeds
light purple onion boasts 2" bulbs - ready to be sliced into a savory summer salad. Can be harvested early like scallions.



Long Day Varieties

shanks grow up to 3 ft. long. Considered a summer leek, it will not winter well in hard-freezing climates.

Spanish Onion -[Hybrid]
Available in white or yellow. These onions are best for northern gardeners.


For Marketing & Culinary purposes theses categories can be further subdivided into  the following

WHITE ONIONS: Glossy white appearance. One of the more pungent onions. Use raw on burgers, sandwiches, salsa and similar dishes if you like warm, but real tasty onions. Otherwise, they can be used in any recipe that calls for cooked onions.

YELLOW ONIONS: Golden color with relatively strong flavor. May be used cooked or raw, depending on your taste for a somewhat pungent onion. Long, slow sautéing at very low heat brings out sweet, mellow flavors.

RED ONIONS: Purplish rather than red, they are relatively mild. Appealing in salads or sautéed in stir fries. Also good for many other recipes. Adding a bit of vinegar, wine or lemon juice helps keep color from fading or turning purplish-blue. You'll often find red onions in salads at restaurants.

SHALLOT: This is not a true onion, it is a small relative of the onion with dry, coppery skin. The flavor combines onions and garlic. Hot when raw, but cooks to a delicate flavor.

SCALLIONS: This is a variety of onions that is harvested before the bulb has formed. Mild flavor. Green onions have tiny white bulbs at the bottom while scallions are younger and have straight white sides at the root end.

LEEKS: In the scallion family. It looks like a large, fat scallion with a white root and dark green, overlapping leaves. Only the root is used. Careful trimming and cleaning are necessary because dirt can accumulate in leaves.

Common pests of most Onion crops are

Root Maggots and Onion Maggots   attack germinating seedlings, they feed on the developing roots and epicotyl. as well as the expanding bulb during later stages of plant development. [Image]

Beet armyworm and Cutworms. Most damage can be avoided by using hardy transplants.Onion plants can  also be protected with Bacillus thuringiensis or spinosad sprays.

Snails and Slugs  Slugs and snails like to feed on young seedlings and succulent parts of plants. They leave a trail of mucus on the surfaces on which they crawl. Moist, humid environments favor slug development, and slugs usually overwinter in sheltered locations outdoors

Leafhoppers and leaf miners are also minor pests of Onion Plantings.

Aphids are Yellowish-pink to pale green plant lice that suck ......plant juices. They are a soft-bodied, oval/pear shaped insect and are commonly found on nearly all varieties of plants, vegetables, field crops, and fruit trees. [Images Hot Pepper Wax repels bugs from your plants, fruits and flowers. 100% natural spray uses pepper extract and wax to effectively discourage pests. Helps to reduce stress on cuttings.

Most onions are also susceptible to fungal infestations, at times it can be a severe problem , particularly under moist conditions.



Botrytis Neck Rot  a major disease of onions. Susceptibility varies by variety. In general, white cultivars are moresusceptible, red and yellow cultivars may also sustain heavy damage. Symptoms generally appear after harvest, although infections occur in the field. The fungus enters bulbs through the neck when the tops are cut  .A gray mold develops between the onion scales and black sclerotia may develop around the neck of the bulb. Secondary invasion by soft rot bacteria may cause a watery rot






Botrytis Leaf Blight occurs in poorly drained damp areas. The bacteria is spread by garden tools and surface water .Bacterial leaf blight usually occurs only on the upper leaves. Small water-soaked lesions form and eventually coalesce into larger lesions that eventually cover the entire leaf.  See Botrytis Leaf Blight Disease Cycle


Downy Mildew [ Image]  See: Cornell Veg. MD online  University of Calif. Onion and Garlic
Downy Mildew

Pink Root  Infected roots first turn light pink, then darken through red and purple, shrivel, turn black, and die. The pinkish red discoloration may extend up into the scales of the bulb. New roots also may become infected. If infection continues, plants become stunted. The disease seldom results in plant death. Infection is confined to roots and outer scales of the bulb. Severe infection will reduce bulb size.

Purple Blotch  usually infects dead or dying leaf tissue. The initial symptoms are small, pale, sunken lesions. These lesions develop purple centers . The infection can encompass much of the leaf, leading to the death of tissue above the lesion. This disease can be controlled with fungicides.

Black Mold occurs sporadically but is potentially serious. It causes damage primarily to stored onions, rendering them unpalatable and unmarketable.

References -

Identification of Diseases and Disorders of Onions  

Colorado State Univ. Botrytis, Downy Mildew and Purple Blotch of Onion

Harvesting and Storage of Onions

Onions will store better if they are dried for several days outdoors, away from direct sunlight.

  • Leave the tops on the bulbs during drying.
  • After drying, cut tops within an inch of bulb.
  • Fresh sweet onions can be stored for several weeks in a cool, dark place. They can be stored in the refrigerator, but do not put them in plastic bags. This will inhibit air circulation.
  • Storage onions should be dried for a longer period of 10 to 14 days. After cured, the tops can be removed and onions stored in mesh bags, or dried tops can be braided into a string of onions.


Canning onions

  • It's best to use onions with a 1-inch diameter or less.
  • Wash and peel onions.
  • Cover with boiling water.
  • Bring to a boil for 5 minutes.
  • Pack the onions into hot jars, leaving an inch of headspace.
  • Add ½ teaspoon salt to pints, 1 teaspoon to quarts
  • Remove air bubbles. Wipe jar rims. Adjust lids and process both pints and quarts at 10 pounds pressure for 40 minutes.


Freezing Onions

  • Bulb onions - store well in a cool, dry place. Freezing is not recommended.
  • Choose mature bulbs , Clean thoroughly.
  • Water blanch for 3 to 7 minutes or until center is heated.
  • Cool promptly, drain and package, leaving a half inch headspace. Seal securely, Then freeze.
    These will be suitable for cooking not eating as is.
  • Green onions may be chopped and frozen without blanching,

See also Pickling and Onion Recipes



Egyptian Onions

Plant Talk - Growing Onions from Seed