- Species and varieties: Onions (Allium cepa) and leeks (Allium ampeloprasum) are both part of the Allium family. Common varieties of onions include yellow onions, red onions, and white onions. Leeks are typically categorized by their growing season, such as summer leeks and winter leeks.
- Hybrid or heirloom: Both onions and leeks can be found in hybrid and heirloom varieties. Hybrid varieties are often bred for disease resistance and uniformity, while heirloom varieties are valued for their traditional flavors and adaptability to local growing conditions.
- Pruning and training: Onions do not require pruning, but it's important to keep the area weed-free to reduce competition for nutrients. Leeks may benefit from hilling, which involves mounding soil around the base of the plants to blanch the stems and produce a longer white shaft.
- Fertilization needs: Both onions and leeks benefit from a balanced fertilizer applied at planting and periodically throughout the growing season. High nitrogen fertilizers can promote leafy growth, while phosphorus and potassium support root and bulb development. Organic matter, such as compost, can also improve soil fertility and structure.
- Hardiness zones: Onions and leeks are generally suitable for USDA hardiness zones 3-9. They can tolerate a range of climates but perform best in cooler weather.
- Climate requirements: Onions and leeks prefer full sun and well-drained soil. They thrive in temperatures between 55-75°F (13-24°C). Onions require a period of cool weather to form bulbs, while leeks can tolerate colder temperatures and are often harvested in late fall or winter.