Growing Onions for the Home Garden: Your First Crop From Seed to Storage

Onions are one of the most practical vegetables a beginner can grow. They require almost no special equipment, they grow in containers and raised beds as well as in-ground plots, and once harvested they will store for months in a pantry without electricity or refrigeration.

This guide covers everything a Zone 7a beginner needs to know about growing onions at home. It is written for gardeners in the Louisville, Tennessee area, which has an average last frost date around May 15 and a first frost around October 15.

Why Onions Belong in Every Beginner Garden

Onions are not one of the flashier garden crops. They do not have the appeal of a basket full of tomatoes or the drama of a massive squash vine. But they reward attention with consistency.

A well-managed onion bed will produce dozens of bulbs with very little effort. They do not need staking, trellising, or complex support systems. They tolerate a wide range of soil types. They grow in shade better than most vegetables, which means they work in beds that do not get full-day sun. And they feed you for a long time after harvest.

Fresh onions have a sweetness and complexity that store-bought onions cannot match. A lot of the onions you buy at the grocery store have been stored for months, shipped long distances, and often have their roots and tops cut off in ways that shorten their life. A homegrown onion from your first garden will taste like something entirely different.

Onions also teach you the most important skill in the beginner garden: patience. They grow slowly at first, put on little visible growth for weeks or even months, and then suddenly begin swelling. Knowing how to care for them through the quiet early stages is a habit that pays off with every slow-growing crop you grow in the years ahead.

Choosing the Right Onion Type for Zone 7a

Onions are divided into three categories by day-length requirement. This is the single most important factor in choosing which variety to grow, because planting the wrong type will result in a garden that produces plenty of leaves but very few bulbs.

Short-day onions

Short-day onions form bulbs when daylight reaches about eleven to thirteen hours per day. In Zone 7a, the sun reaches this length around mid-March to mid-April. Short-day varieties are planted in late summer or early fall so they develop a small root system before winter, then produce bulbs in spring as the days lengthen.

If you plant short-day onions in spring, they will usually not form proper bulbs. They need the cooling temperatures of late fall and winter to trigger bulb formation after the days get long.

Best short-day varieties for the Southeast:

• Texas Early Granex: One of the most widely grown short-day onions. Fast maturing, mild flavor, and reliable. Good for fresh eating and cooking.
• Granex 33: The variety that many grocery stores source their sweet onions from. Very mild flavor, good storage life for a sweet variety.
• Red Westfield: A red onion that performs well as a short-day variety. Adds color to salads and sandwiches.
• Stevenson: Another solid short-day variety with good keeping quality.

Long-day onions

Long-day onions form bulbs when daylight reaches about fourteen to sixteen hours per day. In Zone 7a, this happens around mid-June to mid-July. Long-day varieties are planted in early spring and mature in mid-to-late summer.

Planting a long-day onion in Zone 7a is possible, but the window is tight. You need to plant sets or transplants very early, and the bulbs will not form until July, which means harvesting happens late in the growing season. Some gardeners in Zone 7a find it more reliable to grow short-day varieties and plant a second batch of long-day varieties if they want extra storage bulbs.

Best long-day varieties:

• Ails Craig: A classic long-day sweet onion with good flavor.
• Walla Walla: Very sweet, mild flavor. Grows large bulbs. Best grown in northern climates, but some gardeners in Zone 7a get decent results.
• Texas 1015Y: A heavy producer that forms large bulbs.

For a beginner in Zone 7a, short-day varieties are the safest choice. They have a wider planting window, more reliable bulb formation, and produce during a more comfortable harvest period.

Day-neutral onions

Day-neutral onions are bred to form bulbs regardless of day length, as long as other conditions are right. They can be planted in spring and will form bulbs as the plant reaches maturity, without depending on specific daylight hours.

They are a reasonable middle ground, but they are not as widely available as short-day or long-day varieties, and they do not perform as consistently as short-day onions in Zone 7a. If you find a day-neutral variety you like, it is worth trying. Do not expect it to outperform a proven short-day variety.

Sets, Transplants, or Seed: How to Plant Onions

Onions can be started three ways, and the method you choose depends on how much time you have and how much you want to spend.

Onion sets

Onion sets are small, dormant bulbs that you buy already formed. They look like small onions, usually about the size of a golf ball or smaller. You plant them directly in the ground, and they start growing immediately because they have already done the first stage of development.

Pros:

• Easiest method for beginners
• Fastest results
• Reliable germination (there is nothing to germinate. They are already grown).
• Affordable

Cons:

• Smaller bulb potential than transplants or seed
• Higher chance of bolting (sending up a flower stalk instead of forming a bulb) if the sets are too large or exposed to cold after planting
• Limited variety selection at garden centers

For most Zone 7a beginners in late May, sets are the best starting point. Buy sets that are no larger than a pencil eraser. Larger sets are more likely to bolt. Keep the sets in a cool, dry place until you plant them.

Planting time for sets in Zone 7a: Mid-May to early June is ideal. The soil is warm, frost danger has passed, and the days are long enough to support growth through the summer.

Transplants

Transplants are young onion plants that have been started from seed and grown to about six inches tall. They are sold in bundles, usually twelve to twenty per bundle, at garden centers and nursery stores.

Pros:

• Larger bulb potential than sets
• More variety selection
• More established roots than sets

Cons:

• Slightly more expensive than sets
• More fragile during planting. You need to handle the roots gently.
• Need to be planted quickly after purchase, because they do not store well out of the ground

If your garden center carries onion transplants in late May or early June, they are a solid second choice. Plant them the same day you buy them if possible.

Planting time for transplants: Mid-May to early June, same as sets.

Seed

Starting onions from seed gives you the widest variety selection and the best potential for large bulbs. But it also requires more time, planning, and care. You would need to start seeds indoors in January or February, harden them off in April, and transplant them in May.

Pros:

• Most variety options available
• Best potential for large bulbs
• Lowest cost per plant

Cons:

• Requires starting indoors months ahead
• More delicate during transplanting
• Not practical for most beginners in late May

If you are just starting out and it is already mid-May, skip seed for onions. Grow from sets or transplants. You can try seed next season.

Spacing, Soil, and Where to Put Them

Onions are not demanding about soil, but they do grow best in loose, well-drained ground. They do not like heavy, waterlogged soil. If your soil is heavy clay, work in some compost or aged leaf litter to improve drainage before planting.

Onions prefer a soil pH between 6.0 and 7.0. If you have not tested your soil, a basic kit from a garden center will tell you where you stand. If your soil is too acidic, add some garden lime a few weeks before planting.

Spacing

Space onion plants four to six inches apart in every direction. Rows should be twelve to eighteen inches apart. Do not crowd onions. Tight spacing reduces bulb size and increases the risk of fungal disease.

Each onion needs room to expand as the bulb swells. If you plant them too close together, the bulbs will be smaller and harder to store.

Where to plant

Onions grow in full sun to partial shade. They do best with at least six hours of direct sunlight, but they will tolerate less than tomatoes or peppers. This makes them a good crop for beds that are on the shadier side of a fence or under a small tree.

They are a good fit for raised beds, containers, and in-ground plots. In containers, use a pot at least eight inches deep and eight inches wide, and plant one onion per gallon of soil.

Planting method

Plant sets or transplants one inch deep, with the pointy end facing up. If you are unsure which end is up, plant them on their side. They will figure it out. Firm the soil gently around each plant and water immediately after planting.

Do not bury them deeper than one inch. Deep planting slows growth and can cause rot.

Care Through the Growing Season

Once your onions are in the ground, the work is relatively simple. The main things they need are consistent moisture, a few weedings, and patience.

Watering

Onions need about one inch of water per week, from rain or irrigation. They have shallow roots, so the soil should stay evenly moist but not soggy. Water at the base of the plants, not from above, to reduce the risk of fungal disease.

If you are using drip irrigation or soaker hoses, they are ideal for onions. If you water by hand, aim for a steady soak rather than light daily sprinkling, which encourages shallow roots.

Fertilizing

Onions are moderate feeders. They benefit from a balanced fertilizer at planting time, but they do not need heavy nitrogen applications like tomatoes or corn.

If your soil already has good organic matter, you may not need to fertilize at all. If you want to give the plants a boost, work a balanced fertilizer into the soil at planting time or side-dress with compost about four weeks after planting.

Too much nitrogen will produce big leafy plants with small bulbs. If your onions look lush and green but the bulbs are not swelling, reduce fertilizer and focus on consistent watering instead.

Weeding

Keep the area around onions clean through the first two months of growth. Onions have thin, weak stems and do not compete well with weeds early on. Hand-weed carefully, because onion roots are close to the surface and easy to damage with a hoe.

Once the onion plants are established and the leaves are several inches tall, they will shade out most weeds naturally.

Mulching

A thin layer of mulch around the plants helps retain moisture and suppress weeds. Straw, shredded leaves, or pine straw all work. Keep the mulch a couple inches away from the stems to prevent rot.

Common Problems

Onions are generally pest-resistant, but a few issues show up regularly in home gardens.

Onion maggot

Onion maggot is a small white fly whose larvae burrow into onion bulbs, causing wilting and eventual death. The adult fly lays eggs near the base of the plant in spring.

Prevention: Cover newly planted sets with a floating row cover for the first few weeks. This keeps the flies away from the soil. Remove the cover once the plants are established and have several inches of growth.

Thrips

Thrips are tiny insects that feed on onion leaves, leaving silver or brown streaks. Heavy infestations can reduce bulb size and weaken the plant.

Prevention: Keep the plants well watered, which makes them more resistant to thrips damage. Check the undersides of leaves regularly. If you find thrips, a strong spray of water from the hose will knock them off. Insecticidal soap works too if the infestation is heavy.

Neck rot

Neck rot is a fungal disease that affects the neck of the onion, causing the top to soften and the bulb to deteriorate. It is most common in humid conditions or when plants are harvested too early.

Prevention: Good air circulation between plants, avoiding overhead watering, and allowing bulbs to mature fully before harvest all reduce the risk of neck rot.

Bolting

Bolting is when an onion sends up a flower stalk instead of forming a bulb. It is usually triggered by cold temperatures during the early growth stages or by planting sets that are too large.

Prevention: Use sets that are pencil-eraser sized or smaller. Plant them at the right time, not too early when the ground is still cold, and not too late when the plant has already had a growth cycle.

If an onion bolts, you cannot stop it. The bulb will not form properly. Pull the plant and use the leaves (they taste like mild green onions) or the flower stalk in cooking. Do not leave bolting onions in the ground, because they will not produce storage bulbs.

Harvesting: Knowing When Onions Are Ready

This is the part where most beginners make a mistake. They wait too long, or they do not know when the plant is actually ready.

Onions tell you when they are ready through a clear visual signal. As the bulb finishes swelling and the plant shifts energy from leaf growth to bulb development, the tops begin to yellow and then fall over. This is called "laying down."

When about half of your plants have their tops laid down, it is time to plan for harvest. Give the rest a week or two. Do not pull the onions early, because they need the tops to continue filling out the bulb.

Harvesting method:

1. Choose a dry day for harvest. Wet soil sticks to bulbs and makes curing harder.
2. Gently lift the bulbs from the ground with a digging fork or by hand. Do not pull by the tops, because you can tear the neck and shorten storage life.
3. Brush off excess soil. Do not wash the onions.
4. Leave the tops and roots attached during curing. You can trim them after the curing process is complete.

Curing and Storing Your Harvest

Proper curing and storage are what make onions useful for months. An onion that is harvested and stored without curing will rot in a few weeks. An onion that is cured and stored properly will keep for six months or longer.

Curing

Curing means letting the onions dry in a warm, dry, well-ventilated place so the outer layers become papery and the neck seals shut. This creates a natural protective barrier that keeps moisture out and pathogens away.

Spread the onions in a single layer on a screen, rack, or clean tarp in a dry, shaded area with good air circulation. A covered porch, shed, or garage works well. Do not let them sit in direct sun, which can cook the bulbs.

Let them cure for two to four weeks. They are ready when the outer skin is papery, the neck is completely dry and closed, and the roots are shriveled. You should be able to hear a slight rustle when you rub the outer layers together.

Trimming after curing

Once the onions are fully cured, trim the roots to about half an inch and cut the tops to about one inch above the bulb. Do not trim them shorter than that during the curing process, because an open neck invites rot.

Storage

Store cured onions in a cool, dry, well-ventilated place. Ideal storage temperature is forty-five to fifty-five degrees Fahrenheit. A basement, root cellar, or unheated garage in Zone 7a usually works.

Use mesh bags, woven baskets, or wooden crates that allow air to circulate around each bulb. Do not store onions in plastic bags or airtight containers, because trapped moisture causes rot.

Do not store onions with potatoes. Potatoes release moisture that makes onions soft and spoiled faster. Store them in separate containers.

How long they last

Properly cured and stored onions will keep for six to eight months, sometimes longer. Some varieties like Texas Early Granex are more perishable and should be used within two to three months. Storage varieties like Red Westfield or Stevenson will keep longer.

If you find a soft spot on an onion, use it first or cut the affected area away. One bad onion can spoil others in storage if not addressed quickly.

Getting Started Checklist

Here is a simple checklist to follow for your first onion crop:

1. Choose a short-day variety like Texas Early Granex or Granex 33
2. Buy sets no larger than a pencil eraser (or transplants, if available)
3. Plant in mid-May to early June, after the last frost date
4. Space plants four to six inches apart
5. Plant one inch deep, pointy end up
6. Water about one inch per week
7. Weed carefully during the first two months
8. Add a thin layer of mulch around established plants
9. Watch for bolting and remove any plants that send up flower stalks
10. Harvest when about half the tops have laid down
11. Cure in a dry, shaded, airy place for two to four weeks
12. Trim roots and tops, then store in mesh bags in a cool, dry place

Onions are the kind of crop that makes you feel like a competent gardener quickly. You plant a small bulb in the ground. You water it a few times. A month later you notice the leaves getting taller. Three months later you pull up a perfect onion that looks exactly like the ones you have been buying at the store, except this one cost you less than a dollar to grow and will keep on your counter for months.

Start with one or two rows. See how it goes. You will want more next season.

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— C. Steward 🧥