Best onions to grow in massachusetts

If you’re growing onions in Massachusetts, your best bet is to choose long-day varieties, as they form bulbs when daylight reaches 14 to 16 hours, which happens in our summers. Short-day onions won’t bulb properly here. For reliable yields, plant sets or transplants in early spring, and you’ll be harvesting by midsummer. Here’s what works, and what doesn’t, in our New England soil and climate.

Understanding Onion Day Length

Onions are triggered to bulb by day length. In Massachusetts (zones 5b to 6b), we get long summer days, so long-day varieties are the way to go. These onions need 14 to 16 hours of daylight to form bulbs. Short-day onions, which need 10 to 12 hours, will just grow tops and never bulb properly. Intermediate-day onions (12 to 14 h ours) might work in southern Massachusetts but are less reliable. Stick with long-day for consistent results.

Top Long-Day Onion Varieties for Massachusetts

Here are the varieties that perform well in our region, based on my own trials and feedback from other New England growers.

Variety	Type	Days to Maturity	Storage	Flavor
‘Yellow Sweet Spanish’	Yellow	110	Short to medium	Sweet, mild
‘Walla Walla’	Yellow	125	Short (use fresh)	Very sweet
‘Red Wethersfield’	Red	110	Long	Pungent, sharp
‘Redwing’	Red	110	Long	Mild, sweet
‘Copra’	Yellow	105	Long (up to 9 months)	Strong, good for storage
‘Candy’	Yellow	100	Medium	Sweet, crisp
‘Ailsa Craig’	Yellow	110	Medium	Large, sweet

For storage, ‘Copra’ is my top pick. It keeps well into winter. For fresh eating, ‘Walla Walla’ is a treat, but it doesn’t store. ‘Redwing’ is a reliable red that stores well. If you want a classic yellow for general use, ‘Yellow Sweet Spanish’ is a solid choice.

When and How to Plant Onions in Massachusetts

Onions are cold-hardy, so you can plant them as soon as the soil is workable in early spring, usually late March to mid-April, depending on your zone. In zone 5b, aim for early April; in zone 6b, late March is fine. Soil temperature should be at least 40°F.

You have three options: seeds, sets, or transplants.

• Seeds: Start indoors 8 to 10 weeks before your last frost date (around March 1 in most of Massachusetts). Sow seeds 1/4 inch deep in trays. Harden off and transplant in April. This gives you the widest variety choice.
• Sets: Small bulbs, plant them 1 inch deep, spaced 4 inches apart. Sets are the easiest, but they may bolt (go to seed) if they’re large. Look for sets that are 1/2 inch or smaller.
• Transplants: Buy from a local nursery or online. Plant them 1 inch deep, spaced 4 to 6 inches apart. Transplants are a good middle ground.

For all methods, space rows 12 to 18 inches apart. Onions need full sun (at least 6 hours) and well-drained soil with a pH between 6.0 and 7.0. Work in compost before planting.

Caring for Onions Through the Season

Onions have shallow roots, so they need consistent moisture. Water about 1 inch per week, more in dry spells. Mulch with straw to retain moisture and suppress weeds.

Fertilize with a balanced fertilizer (like 10-10-10) at planting, then side-dress with nitrogen (like blood meal) every 3 to 4 weeks until the bulbs start to swell. Stop fertilizing once the tops begin to fall over.

Weeds are a big issue. Onions don’t compete well. Hand-pull or hoe carefully, as the roots are near the surface.

Harvesting and Storing Onions

Onions are ready when the tops fall over and start to yellow, usually late July to August for long-day varieties. Gently lift them with a fork, let them cure in a dry, shaded spot for 2 to 3 weeks. Then trim the tops to 1 inch and store in a cool, dry, well-ventilated place. For storage onions like ‘Copra’, keep them at 35 to 40°F with low humidity.

Yields: Expect 50 to 80 onions per 10-foot row, depending on variety and spacing. A 10-foot row with 4-inch spacing gives about 30 onions, so plan accordingly.

Common Problems and Solutions

• Bolting: Caused by cold snaps or large sets. Plant sets that are small, and cover with row cover if a hard frost is forecast.
• Onion maggots: These pests lay eggs at the base of plants. Use row covers to prevent egg-laying, and rotate crops.
• Purple blotch: A fungal disease that causes purple spots on leaves. Avoid overhead watering, and space plants for good air circulation.
• Thrips: Tiny insects that cause silvery streaks. Use insecticidal soap or neem oil.

FAQ

Can I grow sweet onions like Vidalia in Massachusetts? No, Vidalia onions are short-day varieties, and they won’t bulb here. Instead, grow ‘Walla Walla’ or ‘Ailsa Craig’, which are sweet but adapted to long days.

What’s the best way to start onions: seeds, sets, or transplants? For beginners, sets are easiest. For variety and storage quality, seeds or transplants are better. I prefer transplants from a local nursery for a head start.

When should I plant onions in zone 5b? Plant sets or transplants in early April, as soon as the soil is workable. For seeds, start indoors in early March.

How do I know when onions are ready to harvest? When the tops fall over and turn yellow, that’s your signal. Don’t wait too long, or they may rot in wet soil.

The Bottom Line

For Massachusetts, choose long-day onion varieties like ‘Copra’, ‘Redwing’, or ‘Yellow Sweet Spanish’. Plant early in spring, keep them watered and weeded, and harvest when tops fall over. With a little care, you’ll have a good crop of onions for fresh eating and storage. Start with sets for ease, or transplants for better variety selection. Happy growing!