Arkansas’s mild winters offer onion seeds a longer growing season than in colder regions. Knowing the best time to start onions seeds in Arkansas is the key to a big harvest of sweet, storage-ready bulbs. If you start them too early or too late, you risk small onions or plants that bolt before they size up.
This guide covers everything you need: exact dates for each zone, step-by-step indoor sowing, and tips for transplanting. You will learn the exact timing for short-day, intermediate-day, and long-day varieties that perform well in the Natural State.
Best Time To Start Onions Seeds In Arkansas
The absolute best time to start onions seeds in Arkansas is between late January and mid-February for most of the state. For southern Arkansas (Zone 7b and 8a), you can start as early as January 15. For northern Arkansas (Zone 6b and 7a), aim for February 1 to February 15.
Starting seeds indoors gives you a 8-10 week head start before transplanting. Onions need cool weather (40-70°F) for bulb development. If you plant seeds directly in the ground, you lose that crucial early growth window.
Here is a quick breakdown by Arkansas growing zone:
- Zone 6b (northwest AR): Start seeds indoors Feb 1-15. Transplant outdoors March 15-April 1.
- Zone 7a (central AR): Start seeds indoors Jan 25-Feb 10. Transplant outdoors March 10-25.
- Zone 7b (south central AR): Start seeds indoors Jan 15-Feb 5. Transplant outdoors March 1-20.
- Zone 8a (southern AR): Start seeds indoors Jan 10-Feb 1. Transplant outdoors Feb 20-March 10.
These dates assume you are using short-day or intermediate-day onion varieties. Long-day onions do not perform well in Arkansas because our summer days are too short for them to bulb properly.
Why Timing Matters So Much For Arkansas Onions
Onions are photoperiod sensitive. They form bulbs based on day length, not just temperature. If you plant seeds too late, the days get long too fast and the onion bulbs stay small. If you plant too early, the seedlings may get leggy or suffer from cold damage.
Arkansas sits in a transition zone. Most of the state is best for short-day onions (like Texas SuperSweet or Red Creole) that bulb when days reach 10-12 hours. Intermediate-day onions (like Candy or SuperStar) also work well in central and northern AR.
Starting seeds at the right time ensures your onions have 4-6 weeks of cool weather after transplanting. That cool period is when roots develop and leaves grow. Warm weather triggers bulbing, so you want maximum leaf growth before summer heat hits.
Choosing The Right Onion Variety For Arkansas
Not all onions are created equal for Arkansas gardens. You need varieties that match our day length and climate. Here are the top performers:
Short-Day Onions (Best For Southern AR)
- Texas SuperSweet – Very sweet, stores 2-3 months
- Red Creole – Spicy flavor, good storage
- Yellow Granex – Classic Vidalia type, short storage
- White Bermuda – Mild, fresh eating only
Intermediate-Day Onions (Best For Central & Northern AR)
- Candy – Large, sweet, stores 3-4 months
- SuperStar – White, mild, great for salads
- Red Candy Apple – Sweet red, stores well
- Cabernet – Red, stores 4-5 months
Avoid long-day onions like Walla Walla or Yellow Sweet Spanish. They need 14-16 hours of daylight to bulb. Arkansas summer days max out at about 14.5 hours in June, so these varieties will produce only small bulbs or no bulbs at all.
Where To Buy Onion Seeds In Arkansas
Local garden centers like Lowe’s, Home Depot, and independent nurseries carry seed packets. Online sources like Johnny’s Selected Seeds, Burpee, and Southern Exposure Seed Exchange offer more variety. Order seeds by early January so they arrive before your planting window.
You can also buy onion sets (small bulbs) for a faster start. Sets are less work but have fewer variety options. If you use sets, plant them 3-4 weeks before your last frost date instead of starting seeds.
Step-By-Step Guide To Starting Onion Seeds Indoors
Follow these steps to get strong, healthy seedlings ready for transplanting.
Step 1: Gather Supplies
- Seed starting mix (light, sterile, drains well)
- Seed trays or small pots (2-3 inches deep)
- Grow lights or a bright south-facing window
- Heat mat (optional but helpful for germination)
- Spray bottle for watering
- Labels and marker
Step 2: Sow The Seeds
Fill your trays with moistened seed starting mix. Sprinkle 3-4 seeds per cell or pot, about 1/4 inch deep. Cover lightly with mix and mist with water. Onion seeds need light to germinate, so do not bury them too deep.
Place the trays in a warm spot (65-75°F). A heat mat speeds up germination. Seeds should sprout in 7-14 days. Keep the soil moist but not soggy.
Step 3: Provide Light Immediately
As soon as you see green shoots, move the trays under grow lights or to a sunny window. Onion seedlings need 12-14 hours of bright light daily. Without enough light, they get leggy and weak. Keep lights 2-3 inches above the seedlings and adjust as they grow.
If using a window, rotate the trays every few days so all sides get light. Consider using a timer to keep the light schedule consistent.
Step 4: Thin And Fertilize
When seedlings are 2-3 inches tall, thin to one strong plant per cell. Snip the extras at soil level with scissors. Do not pull them out, as that disturbs the roots of the remaining plant.
Start fertilizing with a half-strength liquid fertilizer (like fish emulsion or 10-10-10) once a week after thinning. Stop fertilizing 2 weeks before transplanting.
Step 5: Harden Off Before Transplanting
About 10-14 days before your planned transplant date, start hardening off the seedlings. Take them outside for 1-2 hours in a shaded, sheltered spot. Increase time and sunlight exposure gradually each day.
Bring them indoors at night if temps drop below 40°F. After a week, they can stay out overnight if temps are above 35°F. This process reduces transplant shock.
Transplanting Onion Seedlings Outdoors
Once your seedlings are 4-6 inches tall and have 3-4 true leaves, they are ready for the garden. Transplant on a cloudy day or in late afternoon to reduce stress.
Preparing The Garden Bed
Onions need full sun (6-8 hours daily) and well-drained soil with a pH of 6.0-7.0. Work in 2-3 inches of compost or aged manure before planting. Add a balanced fertilizer like 10-10-10 at a rate of 1 pound per 100 square feet.
If your soil is heavy clay, consider raised beds. Onions rot easily in wet soil. Good drainage is critical.
Spacing And Planting Depth
Space onion plants 4-6 inches apart in rows 12-18 inches apart. Dig a small hole deep enough to cover the roots and the white part of the stem. Do not bury the green leaves. Press soil gently around the base.
Water thoroughly after planting. Keep the soil evenly moist for the first 2 weeks while roots establish.
Mulching And Weed Control
Apply a 1-2 inch layer of straw or shredded leaves around the plants. Mulch keeps soil cool, retains moisture, and blocks weeds. Onions have shallow roots, so weeds compete heavily. Hand pull any weeds that appear.
Caring For Onions Through The Season
After transplanting, your main jobs are watering, fertilizing, and watching for pests.
Watering Schedule
Onions need about 1 inch of water per week from rain or irrigation. Water deeply once or twice a week rather than light daily watering. Consistent moisture is key for bulb growth. Drought stress causes small bulbs or early bolting.
Stop watering once the tops start falling over. That signals the bulbs are maturing and excess water can cause rot.
Fertilizing For Big Bulbs
Feed onions every 2-3 weeks with a nitrogen-rich fertilizer like blood meal or fish emulsion. Switch to a phosphorus-potassium blend (like 0-10-10) once bulbs start swelling. Too much nitrogen late in the season makes soft bulbs that store poorly.
Side-dress by sprinkling fertilizer along the row and watering it in. Avoid getting fertilizer on the leaves.
Common Pests And Diseases In Arkansas
- Onion thrips: Tiny insects that suck sap. Use insecticidal soap or neem oil.
- Onion maggots: Larvae that tunnel into bulbs. Rotate crops and use row covers.
- Downy mildew: Gray fuzzy growth on leaves. Improve air circulation and avoid overhead watering.
- Purple blotch: Purple spots on leaves. Remove infected leaves and apply copper fungicide.
Rotate onion crops every 3-4 years to prevent soil-borne diseases. Do not plant onions where garlic, leeks, or shallots grew the previous year.
Harvesting And Storing Arkansas Onions
Onions are ready to harvest when 50-75% of the tops have fallen over naturally. Do not bend the tops yourself, let them fall on their own. That indicates the bulb is mature.
How To Harvest
Loosen the soil with a garden fork, then pull the onions by the tops. Shake off excess dirt but do not wash them. Lay them in a single layer in a warm, dry, shaded spot with good air circulation. A garage or porch works well.
Let them cure for 2-3 weeks until the necks are dry and the outer skin is papery. Cut the tops off leaving 1 inch of stem, and trim the roots. Store in a cool (32-40°F), dry, dark place.
Storage Tips For Arkansas Summers
Arkansas summers are hot and humid, which shortens onion storage life. Sweet onions like Texas SuperSweet only keep 2-3 months. Pungent varieties like Red Creole store 4-6 months. Keep onions in mesh bags or baskets with good airflow. Check regularly and remove any that start to soften or sprout.
For long-term storage, consider dehydrating or freezing chopped onions. They retain flavor well for cooking.
Frequently Asked Questions
Can I plant onion seeds directly in the ground in Arkansas?
Yes, but it is not recommended for best results. Direct seeding in late February or March gives onions less time to grow before bulbing. You will get smaller bulbs. Indoor starts give you a 2-month head start.
What is the last frost date for Arkansas?
Last frost dates vary by zone: Zone 6b (April 10-20), Zone 7a (March 25-April 10), Zone 7b (March 15-30), Zone 8a (March 5-15). Check your local extension office for exact dates.
How long do onion seeds take to germinate?
Onion seeds germinate in 7-14 days at 65-75°F. Cooler soil slows germination. Using a heat mat speeds things up.
Should I soak onion seeds before planting?
Soaking is optional. It can speed germination by a day or two, but it also increases risk of fungal rot if seeds stay wet too long. If you soak, limit to 4-6 hours and plant immediately.
Can I grow onions in containers in Arkansas?
Yes, use a container at least 8 inches deep with drainage holes. Plant seeds or transplants 3-4 inches apart. Containers dry out faster, so water more often. Use a quality potting mix and fertilize regularly.
Final Tips For Success
Start your seeds on time and you will have onions ready by June or July. Keep a garden journal with planting dates and weather notes. That helps you adjust timing next year based on your specific microclimate.
Join a local gardening group or check with the Arkansas Cooperative Extension Service for zone-specific advice. They often have planting calendars and variety trials for your area.
With the right timing and a little care, you can grow enough onions to last through winter. The sweet taste of homegrown onions is worth the effort. Start planning now, order your seeds, and mark your calendar for the best time to start onions seeds in Arkansas.