When To Plant Onions In Central Texas

If you’re planning your central Texas garden, knowing when to plant onions is one of the most important steps for a successful harvest. Getting the timing right in our unique climate is the key to growing big, sweet, or storage-worthy bulbs.

Onions are a cool-season crop, which means they need to be planted in the fall or very early spring here. Planting at the correct time allows them to establish roots and foliage during the cooler months. This gives them a head start before the intense summer heat arrives, which is when the bulbs begin to form and mature.

For central Texas, the primary planting window is in the fall. The ideal time is from mid-October through mid-December. Planting in fall allows the onion sets or transplants to develop a strong root system over the winter. When spring comes, they are ready to put all their energy into bulbing.

A secondary, but trickier, planting window is in late winter. You can plant from late January through mid-February. This is more common for gardeners who miss the fall window or for growing green onions. Spring-planted onions have a shorter growing season and often produce smaller bulbs, but they can still be a good crop.

Understanding Onion Types: Short-Day vs. Long-Day

This is the most critical factor after timing. Onions form bulbs based on day length, and planting the wrong type will lead to disappointment.

Short-Day Onions: These are the ones you must plant in central Texas. They begin forming bulbs when daylight lasts 10-12 hours, which matches our spring. They are perfect for our southern latitude.
Long-Day Onions: These need 14-16 hours of daylight to bulb, which we don’t get. They will only produce greens and never form a proper bulb here. Avoid these varieties.

Always check the seed packet or plant tag for “short-day” variety. Some excellent short-day choices for Texas include:

Texas Legend (a mild, sweet onion)
Texas Early White (good for storage)
1015Y (The famous “Texas Super Sweet”)
Red Creole (a beautiful, pungent red onion)
Granex (the classic Vidalia-type sweet onion)

How to Plant Your Onions Step-by-Step

Onions grow best in loose, well-draining soil with plenty of sunlight. Follow these steps for the best results.

1. Choose Your Planting Method

You have three options, each with its own pros.

Sets: Small, dormant onion bulbs. They are easy to plant but can bolt (flower) more easily, which ruins the bulb. Choose sets no larger than a dime.
Transplants: Small, live onion plants sold in bunches. This is the most popular and reliable method for central Texas gardeners. You can also start your own seeds indoors in late summer.
Seeds: Planting seeds directly in the garden is challenging due to weed competition and the long growing time. It’s not generally recommended for beginners here.

2. Prepare Your Garden Bed

Onions are heavy feeders. A month before planting, work 2-3 inches of compost into the top 6-8 inches of soil. Add a balanced, slow-release organic fertilizer according to package directions. Rake the bed smooth and remove any rocks or clumps.

3. Planting Depth and Spacing

Proper spacing is crucial for bulb development.

Plant transplants or sets about 1 inch deep. If using transplants, trim the tops back to about 4 inches tall to reduce transplant shock and focus energy on the roots.
Space plants 4-6 inches apart within the row.
Space rows 12-18 inches apart.

Make sure the white part (the bottom with roots) is fully covered, but don’t bury the green shoot to deeply. Firm the soil gently around each plant.

4. Watering and Mulching

Water your newly planted onions thoroughly. After that, aim for about 1 inch of water per week, including rainfall. Drip irrigation or soaker hoses are ideal to keep foliage dry and prevent disease.

Apply a 2-3 inch layer of organic mulch, like shredded leaves or straw, around the plants. This conserves moisture, suppresses weeds, and insulates the soil over winter. It’s a step many gardeners forget, but it makes a huge difference.

Caring for Your Onion Crop Through the Seasons

Fall and Winter Care

After planting in fall, your onions will grow slowly. Their main job is root development. Water during dry spells, but be careful not to overwater in cool weather. Pull weeds promptly, as onions don’t compete well. The mulch will help alot with this.

Spring Feeding and Growth

As temperatures warm in February and March, your onions will begin rapid top growth. This is when they need the most nutrients. Side-dress them with a nitrogen-rich fertilizer, like blood meal or a balanced organic blend, when they are about 6 inches tall. Repeat this feeding every 3-4 weeks until the bulbs begin to form.

Stop fertilizing once you see the soil begin to crack and bulge around the forming bulb. At this point, to much nitrogen can hurt bulb development and storage quality.

Knowing When to Harvest

Harvest time in central Texas is typically from late April through early June. Watch for these signs:

The tops (leaves) begin to turn yellow and fall over naturally.
The neck, just above the bulb, becomes soft.
The outer skin on the bulb becomes papery.

When about half the tops have fallen over, you can gently push over the rest to signal the plant to stop growing. Don’t break the stems off.

Curing and Storing Your Harvest

Proper curing is essential for storage onions. Pull them up on a dry, sunny day.

Lay them in a single layer in a warm, dry, well-ventilated spot out of direct sun. A covered porch or garage works well.
Let them cure for 2-3 weeks until the necks are completely dry and tight, and the outer skins rustle like paper.
Trim the roots and cut the tops back to about 1 inch.

Store cured onions in a cool, dry, dark place in mesh bags or a single layer. Check them occasionally and use any that show signs of softening first.

Common Problems and Solutions in Central Texas

Bolting (Flowering): Caused by stress from temperature swings or planting too large of sets. Once a onion sends up a flower stalk, the bulb is done growing and won’t store well. Use that onion soon in the kitchen.
Small Bulbs: Usually from planting the wrong day-length type, overcrowding, insufficient nutrients, or planting too late in the spring.
Pests: Thrips are the main insect pest. They cause silvery streaks on leaves. Control with a strong spray of water or insecticidal soap. Onion maggots are less common but can be deterred by crop rotation.
Diseases: Fungal issues like downy mildew or purple blotch can occur in wet, humid weather. Ensure good air circulation, avoid overhead watering, and rotate where you plant onions each year.

FAQ: Planting Onions in Central Texas

Can I plant onions from the grocery store?
It’s not recommended. Those are often long-day varieties and may have been treated to prevent sprouting. You’re better off buying known short-day sets or transplants from a local nursery.

What’s the best onion to grow in Central Texas?
The 1015Y (“Texas Super Sweet”) is famous for a reason—it’s bred for our climate and is reliably sweet and large. Texas Legend and Granex are also excellent, consistent performers.

How late is too late to plant onions?
If you miss the fall window, you can try planting transplants up until about mid-February. After that, the growing season is to short to produce a good-sized bulb before the heat sets in.

Should I grow onions from seed?
Starting from seed gives you the most variety choice, but it requires starting indoors 8-10 weeks before your fall planting date (around August). For most gardeners, buying transplants is the easiest and most succesful route.

Why are my onion tops falling over in winter?
A little tip burn from cold snaps is normal and nothing to worry about. If the whole plant collapses, it could be from overly wet soil or disease. Ensure your soil drainage is good.

Can I grow green onions (scallions) year-round?
Almost! You can succession plant short-day varieties for green onions throughout the fall, winter, and early spring. They are harvested young before bulbing, so timing is less critical. They may bolt in the peak of summer heat.

Growing onions in central Texas is deeply rewarding. By planting the right short-day variety at the right time—primarily in the fall—and giving them simple, consistent care, you’ll be able to enjoy a homegrown staple that stores for months. Paying attention to soil preparation, spacing, and that critical harvest and cure process will ensure your efforts are rewarded with a plentiful and tasty crop.