Onion in Zone 8B — Texas

Growing onions in Zone 8B Texas gives you access to sweet, mild bulbs that store well through our long growing season. The key advantage here is our early spring allows you to get onions established before the brutal Texas heat arrives, and our 273-day growing season means you can grow both short-day and intermediate-day varieties successfully. Nothing beats the satisfaction of pulling your own cured onions from storage in January, knowing they were grown through Texas's unpredictable weather.

While our extreme heat and drought can stress onion bulbs during summer, proper timing makes all the difference. Plant early enough in spring to let bulbs size up before peak heat, and you'll harvest plump onions that rival anything from the store. The trick is working with our climate, not against it.

Starting onion seeds indoors makes sense if you want the largest possible bulbs and don't mind the extra work. Sow seeds in late November through mid-December, about 10 weeks before you'll transplant them outside in mid-February. This timing lets you take advantage of our early spring while giving seeds a controlled environment during winter.

Set up seed trays in a warm spot (65-75°F) with good light once they germinate. Bottom watering works best since onion seedlings are prone to damping off when their stems stay wet. The seedlings will look like thin grass at first, which is perfectly normal.

Honestly, most Texas gardeners skip this method since onion sets are so much easier, but if you want specific varieties or the biggest bulbs, starting from seed indoors gives you that option. Just be prepared for the long commitment from late November through harvest.

Transplant your onion seedlings outside from mid-February through early March, after they've been hardened off for about a week. This timing gets them established before our spring heat really kicks in. Space them 4-6 inches apart in rows, planting them at the same depth they were growing in their containers.

Harden off seedlings gradually by setting them outside for a few hours each day, bringing them in if overnight temperatures threaten to drop below freezing. Once they're acclimated, they can handle our typical late winter temperature swings just fine.

The reality is that most Texas gardeners use onion sets instead of seedlings since they're more reliable and easier to handle. Sets are small bulbs that establish faster and are less likely to be damaged by unexpected late freezes or our variable spring weather.

Direct sowing onion seeds works in Texas, but timing is everything. You can sow from late January through early August, though spring plantings (late January through March) give the best results. Wait until soil temperature reaches at least 50°F and the ground isn't muddy from winter rains.

Prepare your bed with loose, well-draining soil since onions hate wet feet. Sow seeds about half an inch deep and 4-6 inches apart, or plant them closer and thin later. Seeds germinate slowly in cool soil, often taking 2-3 weeks, so don't panic if nothing shows up immediately.

Direct seeding works better with sets than actual seeds in Texas. Plant onion sets (small bulbs) pointed end up, just barely covered with soil. They establish quickly and give you a head start over seeds, which matters when you're racing against our early heat.

Onions need consistent moisture during their bulb formation period, which happens during our spring months before the real heat hits. They're not drought tolerant, so you'll need to stay on top of watering as temperatures climb. Use the finger test – if the soil is dry 2 inches down, it's time to water.

During spring establishment (February through April), aim for about 1 inch of water per week, including rainfall. As temperatures climb into the 90s and above, you might need to water twice weekly since our variable humidity and unpredictable rainfall can leave plants stressed. Water at the base rather than overhead to avoid encouraging fungal problems in our humid conditions.

Watch for signs of water stress – the tips of onion leaves turn yellow and die back when plants are too dry. Overwatering shows up as yellowing from the base up, plus soft, mushy bulbs. Stop watering altogether when the tops start falling over naturally (usually late spring to early summer) – this signals the bulbs are ready to cure.

A 2-inch layer of mulch helps retain moisture and keeps soil temperatures down during peak summer heat, but keep mulch a few inches away from the bulbs themselves to prevent rot in humid conditions.

Your first onions will be ready from early May through early December, depending on when you planted and which varieties you chose. The classic harvest sign is when the green tops start falling over and yellowing – this usually happens about 100 days from planting. Don't wait for all the tops to fall; harvest when about half have gone down.

Pull bulbs on a dry day if possible, brushing off excess soil but leaving roots and tops attached. Let them cure in a warm, dry, well-ventilated area for 2-3 weeks before trimming. Our Texas heat actually helps with curing, just make sure they're out of direct sun and rain.

You can harvest smaller onions earlier as "green onions" throughout the growing season, which is handy when spring heat comes early and threatens to stress the plants. These young onions are tender and mild, perfect for fresh use.

As first frost approaches in late November, harvest any remaining bulbs regardless of size. They won't grow much more once temperatures consistently drop below 50°F, and it's better to cure small onions than lose them to freeze damage.

Onion Thrips These tiny insects create silvery streaks and stippling on onion leaves, eventually causing tips to turn brown and die back. The damage looks like tiny scratches running along the leaf surface, and you might see the small, yellow-brown thrips if you look closely. Thrips thrive in our hot, dry Texas summers and can quickly weaken plants when populations explode. Control them with beneficial insects like lacewings, or spray with insecticidal soap early in the morning when temperatures are cooler.

Pink Root This fungal disease turns onion roots pink to purple, then they shrivel and die. Plants become stunted with yellowing leaves, and bulbs stay small. Pink root loves our Texas heat and humidity, especially in poorly draining soils. Prevent it by ensuring good drainage, rotating crops (don't plant onions in the same spot for 3-4 years), and choosing resistant varieties. Once you see symptoms, there's no cure – pull affected plants immediately.

Bolting When onions send up flower stalks prematurely, the bulbs become bitter and won't store well. You'll see a thick, central stalk emerging with a round flower head on top. This typically happens when plants experience stress from our extreme heat, drought, or dramatic temperature swings. Prevent bolting by choosing the right day-length varieties for Texas (short to intermediate day), planting at the proper time, and keeping soil consistently moist during hot weather.

Texas Specific Challenges: Our unpredictable weather – from late freezes to sudden heat spikes to flash floods – can stress onions into bolting or make them susceptible to root diseases. The extreme summer heat that regularly hits 97°F and above means you need to get bulbs sized up early in the season, and our variable humidity creates perfect conditions for fungal problems when combined with inconsistent rainfall.

Plant onions alongside carrots, beets, lettuce, and tomatoes for the best results in Texas gardens. Carrots and onions make classic companions because onions repel carrot flies while carrots help break up soil for onion root development. Beets and lettuce appreciate the pest-deterrent qualities of onions, plus these cool-season crops can be harvested before onions need full space in late spring. Tomatoes benefit from onions' ability to repel certain pests, and since you can grow two tomato seasons in Texas, onions planted early will be finishing up as you set out fall tomatoes.

Avoid planting onions near beans and peas, as onions can inhibit the nitrogen-fixing bacteria these legumes depend on. This is especially important in Texas since our long growing season means you might be tempted to succession plant beans near established onions – resist the urge and give them separate garden areas.