How to Select the Best Onions & Leeks

Growing Onions and Leeks: A Guide to Your Best Harvest Yet

Onions and leeks are not only versatile kitchen staples but also essential additions to any vegetable garden. To achieve the biggest, healthiest bulbs, two critical factors come into play: choosing the right type of onion for your region and deciding whether to grow from transplants, sets, or seeds. With careful planning and execution, you’ll be on your way to a bountiful harvest.

Choosing the Right Onion for Your Region

The first step in growing successful onions is selecting a variety that matches the day length and climate of your location. Onions are sensitive to sunlight and temperature, which determine their bulb formation.

Day-Length Requirements

Onions are classified into three main types based on their day-length requirements:

1. Long-Day Onions

   • Require at least 14 hours of sunlight to form bulbs.
   • Thrive in cooler climates and northern regions.
   • Typically planted in spring and harvested in late summer.
   • Unsuitable for southern regions, as they won’t receive enough sunlight to develop large bulbs.

2. Short-Day Onions

   • Require 12 hours of sunlight for bulb formation.
   • Ideal for southern regions with mild winters.
   • Planted in fall to over-winter, with bulbs forming in spring as days lengthen.
   • Poor performers in northern regions, as they bulb up too early, resulting in undersized bulbs.

3. Intermediate-Day (Day-Neutral) Onions

   • Form bulbs with 12 to 14 hours of daylight.
   • Can be grown in most zones except for extreme southern areas like south Florida and south Texas.
   • Versatile planting options, depending on regional weather conditions.

Leeks

Unlike onions, leeks are not dependent on day length and can be grown in most gardening zones.

For more information on onion day lengths, read this post and watch our video.

Growing Onions from Sets, Transplants, or Seeds

Once you’ve chosen the right onion variety for your region, the next step is deciding whether to grow from sets, transplants, or seeds. Each method has its benefits and challenges.

Shop Onion Sets

Growing from Sets

Onion sets are immature bulbs harvested early and stored for later planting.

• Best for: Gardeners looking for a quick start.
• Pros:
  • Convenient to store and easy to plant.
  • Suitable for planting in spring or fall.
  • Provide extra months of growing time.
• Cons:
  • Limited to long-day varieties.
  • Prone to bolting (premature flowering).
  • Often better for growing scallions rather than full-sized bulbs.

Growing from Seeds

Onion seeds offer the most variety and flexibility for onion and leek cultivation.

• Best for: Gardeners seeking specific colors, flavors, and shapes.
• Pros:
  • Available in short-, intermediate-, and long-day varieties.
  • More resistant to disease.
  • Produce onions with longer storage life.
• Cons:
  • Require a longer growing season.
  • More challenging to germinate and grow.

Tips for Growing from Seeds:

• Start seeds indoors before the last frost for transplanting, or sow directly into the garden as soon as the soil is workable.
• Plan for a longer growing season to allow seeds to mature into large bulbs.

Growing from Transplants

Onion transplants are seedlings started in controlled environments and sold ready to plant.

• Best for: Gardeners who want a head start without starting from seed.
• Pros:
  • Easier to grow than seeds.
  • Available in various day-length types.
  • Provide a quicker harvest than seeds.
• Cons:
  • Slightly more expensive than seeds or sets.

Tips for a Successful Onion and Leek Harvest

Follow these best practices to maximize your onion and leek yields:

1. Soil Preparation

• Ensure the soil is loose, well-drained, and rich in organic matter.
• Maintain a soil pH of 6.0 to 6.8 for optimal growth.

2. Fertilization

• Apply a nitrogen-rich fertilizer during the growing season to promote leaf development, which directly impacts bulb size.
• Reduce nitrogen levels once bulbs start forming to prevent soft, poorly storing onions.

3. Watering

• Keep the soil consistently moist but not waterlogged.
• Reduce watering as the bulbs mature to prevent rot and enhance storage quality.

4. Weed Control

• Onions and leeks have shallow root systems, so weeds can compete for nutrients and water. Regular weeding is essential.

5. Mulching

• Apply a layer of mulch to retain soil moisture, regulate temperature, and suppress weeds.

6. Proper Spacing

• Space onion plants 4 to 6 inches apart to give bulbs room to grow.
• Leeks can be spaced closer together, about 2 to 4 inches apart.

Harvesting and Storage

Onions

• Harvest onions when the tops begin to yellow and fall over.
• Cure them by laying them in a dry, shaded area for 10 to 14 days until the necks are completely dry.
• Store in a cool, dry, and well-ventilated area for extended shelf life.

Leeks

• Harvest leeks when they reach a desirable size, typically when stems are 1 to 2 inches thick.
• Leeks do not require curing and can be stored in the refrigerator for several weeks.

Final Thoughts

Onions and leeks are rewarding crops that add flavor and nutrition to your meals. By selecting the right day-length variety, choosing an appropriate planting method, and following proper care practices, you can enjoy a successful harvest. Whether you prefer the convenience of sets, the variety of seeds, or the head start of transplants, onions and leeks are versatile additions to any garden.

Start planning your onion and leek garden today, and savor the satisfaction of growing your own flavorful harvest.