When To Plant Onions In Zone 8b

Knowing when to plant onions in zone 8b is the first step to a fantastic harvest. This guide will walk you through the optimal planting season and everything you need to get it right.

Gardening in zone 8b is a joy, with its long, mild growing season. For onions, timing is everything. Plant at the right moment, and you’ll get big, beautiful bulbs. Miss the window, and you might end up with small onions or ones that don’t form properly.

Let’s get your onions in the ground at the perfect time.

The core rule for zone 8b is to plant onions in the fall or very early spring. Onions are cool-season crops. They need to establish roots and grow tops before the heat of summer triggers bulbing.

Here are your two best planting windows:

Fall Planting (Recommended): Plant onion sets or transplants between October and November. The goal is to get them settled in before the ground freezes. They’ll put down roots over the winter and be ready to explode with growth in early spring, giving you an earlier and often larger harvest.
Spring Planting: Plant as soon as the soil is workable, typically from late January through February. Don’t wait too long; onions need cool weather to develop. If you plant to late in spring, the bulbs won’t have enough time to size up before summer heat arrives.

Understanding Your Onion Type: Day Length is Key

Before you buy any onions, you must understand day length. Onions bulb up based on how many hours of daylight they receive. Picking the wrong type for your zone is a common mistake.

Short-Day Onions: These bulb up when daylight lasts 10-12 hours. They are perfect for southern zones like 8b. Planting them in the fall allows them to mature in the spring.
Intermediate-Day (Day-Neutral) Onions: These need 12-14 hours of daylight. They are also an excellent choice for zone 8b and offer great flexibility for both fall and spring planting.
Long-Day Onions: These require 14-16 hours of daylight and are best for northern states. Avoid these in zone 8b, as they likely won’t bulb properly with your shorter summer days.

Choosing Your Planting Method

You can start onions from seeds, sets (small bulbs), or transplants (seedlings). Each has it’s pros and cons.

Seeds: Most variety options. Best sown directly in fall or started indoors 8-10 weeks before your spring planting date. They require more time and care.
Sets: The easiest and fastest method. These are small, dormant bulbs. They are great for beginners but offer fewer variety choices and can bolt (flower) more easily, especially if planted to early in fall.
Transplants: These are young seedlings, often sold in bunches. They give you a head start and a good variety selection. They are ideal for fall planting in zone 8b.

Step-by-Step Planting Guide

Prepare the Soil: Onions need loose, well-draining soil rich in organic matter. Work in several inches of compost or aged manure. A soil pH between 6.0 and 6.8 is ideal. Raised beds work wonderfully for onions.
Plant Correctly: For sets and transplants, plant them about 1 inch deep. Space them 4-6 inches apart in rows that are 12-18 inches apart. If planting from seed, sow them ½ inch deep and thin later.
Water and Mulch: Water them in well after planting. Apply a light layer of straw or shredded leaves mulch to suppress weeds and retain moisture. This is especially helpful for overwintering fall-planted onions.

Caring for Your Growing Onions

Consistent care through the season leads to successfull bulbs.

Watering: Onions have shallow roots. They need consistent moisture, about 1 inch per week. Reduce watering as the bulbs mature and the tops begin to yellow and fall over, which is a sign they’re nearing harvest.
Fertilizing: Feed them with a nitrogen-rich fertilizer early in the season to support green top growth. Switch to a balanced or phosphorus-heavy fertilizer as bulbing begins. Stop fertilizing once the bulbs start to swell.
Weeding: Keep the area weed-free. Onions don’t compete well for nutrients. Be careful when weeding not to damage the shallow roots or bulbs.

Common Pests and Problems in Zone 8b

Stay vigilant for a few typical issues.

Onion Maggots: These are the larvae of a small fly. They tunnel into bulbs. Use floating row covers to prevent the flies from laying eggs near your plants.
Thrips: Tiny insects that cause silvery streaks on leaves. A strong spray of water or insecticidal soap can help manage them.
Bolting: This is when an onion sends up a flower stalk. Once this happens, the bulb stops growing. Choose bolt-resistant varieties and avoid planting sets to early in fall to minimize risk.

Harvesting and Curing Your Onions

Harvest time is the best reward. Here’s how to do it properly.

Watch for Signs: Onions are ready when about half the tops have naturally turned yellow, brown, and fallen over. Gently bend over any remaining tops to signal the bulbs to stop growing.
Harvest: On a dry day, carefully lift the bulbs with a garden fork. Shake off excess soil, but don’t wash them.
Cure for Storage: This step is crucial. Lay the onions in a single layer in a warm, dry, well-ventilated spot out of direct sun for 2-3 weeks. The necks will tighten, and the outer skins will become papery.
Store: After curing, trim the roots and cut the tops down to about 1 inch. Store in a cool, dry, dark place in mesh bags or a single layer. Properly cured onions from a fall planting can last for many months.

FAQs: Onion Planting in Zone 8b

Can I plant onions in late spring in zone 8b?
It’s not ideal. Planting after March often doesn’t give the bulbs enough cool-weather growth time before summer heat initiates bulbing, resulting in smaller onions.

What are the best onion varieties for zone 8b?
Excellent short-day varieties include ‘Texas Grano’, ‘Red Burgundy’, and ‘Southern Belle Red’. Good intermediate-day choices are ‘Candy’, ‘Super Star’, and ‘Yellow Spanish’.

Should I use mulch for fall-planted onions?
Yes, a light mulch is very beneficial. It protects the young plants from temperature swings over winter and supresses weeds. Just pull it back slightly from the direct base of each plant.

How do I prevent my onions from bolting?
Use transplants or seeds instead of sets for fall planting, as sets are more prone to bolting. Also, choose bolt-resistant varieties and ensure they have consistent water without stress.

Can I grow onions from grocery store scraps?
You can regrow the green tops from a scallion or onion bottom in water for fresh greens, but you won’t get a new full-sized bulb this way. For bulb onions, it’s best to start with seeds, sets, or transplants meant for gardening.

Getting your timing right with the zone 8b onion planting schedule sets you up for a rewarding harvest. By choosing the right day-length variety and providing simple, consistent care, you’ll be pulling up plump, flavorful onions from your own garden. Remember, the extra effort put into proper planting and curing makes all the difference in your final yield.