Everything You Need to Know About Intermediate-Day Super Sweet Onion Sets

The perfect balance of sweetness, size, and adaptability for home gardeners.

Intermediate-day Super Sweet onions are a versatile and popular choice for gardeners looking for a mild, flavorful onion that performs well across a variety of regions. They are especially valued because they strike a balance between short-day and long-day varieties, producing consistent bulbs in both northern and southern climates.

This guide covers everything you need to know about planting, growing, harvesting, storing, and using Intermediate-Day Super Sweet onion sets.

What Are Intermediate-Day Super Sweet Onion Sets?

Intermediate-day Super Sweet onion sets are small, immature onions grown the previous season and dried for replanting. They are specifically bred to produce bulbs when day length reaches 12–14 hours, making them adaptable for a wider range of latitudes compared to long-day or short-day onions.

Key characteristics:

• Mild, sweet flavor ideal for raw eating and cooking
• Crisp texture that holds up in salads and sandwiches
• Medium to large bulb size
• Rapid and reliable growth from sets
• Versatility in various climates

These sets provide home gardeners with a simple, effective way to produce high-quality onions with minimal effort.

Why Grow Intermediate-Day Super Sweet Onion Sets?

✔ Mild Flavor

Ideal for salads, sandwiches, grilling, and fresh consumption without the pungent bite of standard onions.

✔ Versatile Day-Length Adaptation

Intermediate-day varieties grow well in both northern and southern regions, unlike strictly long-day or short-day onions.

✔ Easy and Fast Growing

Using sets instead of seeds reduces growing time and improves success rates for first-time gardeners.

✔ Reliable Yields

Produces consistent, uniform bulbs that store well for several months.

✔ Disease Resistance

Good resistance to common onion pests and diseases like thrips, downy mildew, and pink root.

When to Plant Intermediate-Day Super Sweet Onion Sets

Intermediate-day onion sets are best planted as early as the soil can be worked in spring:

• Soil temperature: 50–75°F
• Outdoor temperatures above 28–30°F
• Soil must be loose, well-drained, and workable

Southern regions: plant in late fall or early spring
Northern regions: plant when the threat of frost has passed

How to Plant Intermediate-Day Super Sweet Onion Sets

1. Prepare the Soil

• Loosen soil to 8–10 inches deep
• Enrich with compost or aged manure
• Ensure soil pH is 6.0–6.8
• Avoid heavy clay or waterlogged soils

2. Planting Depth & Spacing

• Plant sets 1 inch deep
• Space sets 4 inches apart
• Space rows 12–18 inches apart
• Plant with the pointed tip up

Proper spacing ensures adequate airflow and optimal bulb size.

3. Watering

• Water thoroughly after planting
• Maintain consistent moisture during early growth
• Avoid waterlogged soil, which can lead to rot

Care Throughout the Season

✔ Watering

• Provide 1 inch of water per week, adjusting for rainfall
• Maintain consistent soil moisture during bulb formation

✔ Fertilizing

• Apply a nitrogen-rich fertilizer during early top growth
• Switch to a balanced or low-nitrogen fertilizer once bulbs begin to swell
• Avoid excess nitrogen late in the season to prevent soft bulbs

✔ Weeding & Mulching

• Mulch with straw, grass clippings, or shredded leaves
• Keep onions weed-free to prevent competition for nutrients

✔ Pest & Disease Management

• Common issues: onion maggots, thrips, downy mildew, fusarium, pink root
• Preventive measures: crop rotation, proper spacing, removing infected plants, good soil drainage

Harvesting Intermediate-Day Super Sweet Onions

Intermediate-day Super Sweet onions are usually ready 90–120 days after planting.

Signs of maturity:

• Tops turn yellow and fall over naturally
• Bulbs are firm and medium to large in size

How to Harvest

1. Loosen soil gently with a garden fork
2. Pull bulbs carefully to avoid bruising
3. Lay onions in a shaded, well-ventilated area to cure
4. Do not wash before curing

Curing & Storing

✔ Curing

• Cure onions for 1–2 weeks
• Warm (75–85°F), dry, and ventilated area
• Tops and necks must dry completely

✔ Storage

• Cool (35–55°F), dry, and dark environment
• Store in mesh bags, crates, or baskets
• Typically stores 3–4 months depending on conditions

Culinary Uses for Intermediate-Day Super Sweet Onions

• Raw: salads, salsas, sandwiches, and burgers
• Grilled or roasted: caramelizes beautifully
• Sauteed: for soups, stews, and stir-fries
• Pickled: adds sweet flavor to preserved dishes
• Versatile in cooked dishes: mild enough to enhance but not overpower

Frequently Asked Questions

Are Intermediate-Day Super Sweet onions good for beginners?

Yes, sets are easy to plant and grow successfully.

Do they store well?

Yes, up to 3–4 months when properly cured.

How large do the bulbs grow?

Medium to large, depending on soil fertility and spacing.

Can they be grown in containers?

Yes, with at least 12” of loose soil and good drainage.

Are they long-day or short-day onions?

Intermediate-day varieties require 12–14 hours of daylight, making them adaptable across multiple regions.

Tips for Growing Success

• Plant sets early in the season
• Provide full sun (6+ hours/day)
• Mulch to retain moisture and reduce weeds
• Fertilize lightly after early growth
• Maintain consistent watering
• Cure fully before storage
• Rotate crops annually to prevent disease

Intermediate-day Super Sweet onion sets are an excellent choice for gardeners seeking a mild, adaptable, high-yield onion that performs reliably across regions.