Onion starts are young planting material that offer gardeners a faster and more reliable path to harvest than sowing seeds directly into the garden soil. These starts generally come in two forms: onion sets and onion transplants. Onion sets are small, immature bulbs grown the previous season and kept dormant for replanting. Transplants are young seedlings, usually about the size of a pencil, started indoors in trays before being shipped or sold. Choosing starts bypasses the lengthy germination period and the delicate early seedling stage, which increases the likelihood of a successful onion crop.
Selecting the Best Onion Type for Your Region
Successfully growing a large onion bulb depends on selecting the correct photoperiod type for your geographic location. Onion bulbing is a response to day length, meaning the plant needs a specific number of daylight hours to trigger the switch from leaf growth to bulb formation. Planting a variety that requires significantly more or less light than the region naturally receives will cause the plant to either fail to bulb or begin bulbing prematurely, resulting in small harvests. This photoperiodic requirement is categorized into three main types based on the necessary daylight duration.
Short-day onions initiate bulbing when daylight reaches approximately 10 to 12 hours, making them suitable for southern regions located below the 35th parallel. States like Texas, Florida, and Southern California rely on these types, as the short duration allows them to mature before the intense summer heat arrives. Planting a short-day variety too far north will cause it to bulb too quickly while still small, leading to a poor yield because the plant did not have sufficient time for vegetative growth.
Long-day onions require 14 to 16 hours of daylight to trigger bulbing, making them the appropriate choice for northern regions above the 42nd parallel. Gardeners in states such as New York, Washington, and Minnesota should choose these varieties to ensure the plants develop substantial foliage before the long summer days signal bulbing. These plants use the extended daylight hours to maximize photosynthesis and energy storage in the developing bulb structure.
Intermediate-day, or day-neutral, onions require around 12 to 14 hours of daylight, which suits the middle latitudes between the 35th and 42nd parallels. These varieties offer greater flexibility and are often successful in transitional zones like parts of the Midwest and mid-Atlantic states. Confirming your specific latitude and corresponding required photoperiod is essential before purchasing any onion start material.
Retail and Online Sources for Onion Starts
Once the appropriate photoperiod type is determined, gardeners can source their onion starts from local physical stores, such as large home improvement centers and independent garden nurseries. These stores offer immediate accessibility and allow for personal inspection of the material before purchase. They typically stock common varieties well-suited to the immediate area, simplifying selection. However, the variety offered is often limited, especially concerning heirloom or less common intermediate-day types.
Big box stores usually carry onion sets in bulk mesh bags, which are cost-effective but may not always be labeled with the specific cultivar name or photoperiod requirement. Independent garden centers are often more knowledgeable, providing transplants in trays that are clearly labeled with variety and day length. While convenience is high, the window of availability for these seasonal items can be quite short, often only a few weeks in early spring.
For gardeners seeking a wider selection or specific regional varieties, mail-order suppliers and specialty online seed companies are a good alternative. Dedicated onion start suppliers often have dozens of cultivars, including those bred specifically for flavor, storage, or unusual colors, which are rarely found in local stores. These companies provide transplants or sets grown in optimal conditions, ensuring the material is healthy and ready for planting upon arrival.
Ordering online requires planning to account for shipping timelines, as the starts must arrive near the correct planting date for the region. Most reputable online companies pre-schedule shipments based on the customer’s USDA hardiness zone to ensure optimal delivery timing. While the cost may be higher due to shipping and handling fees, the benefit is access to the right onion type for successful bulb formation.
Evaluating the Quality of Onion Sets and Transplants
Inspecting the physical quality of the onion starts before planting helps ensure a successful harvest. When purchasing onion sets, the size of the small bulb is important. Sets should ideally be no larger than a dime, or about a half-inch in diameter. Larger sets are more prone to bolting, which is prematurely sending up a flower stalk. Bolting diverts the plant’s energy away from bulb development, reducing the size and quality of the final product.
Inspection for signs of disease or decay is necessary for both sets and transplants upon acquisition. Onion sets should feel firm and dry; white fuzzy growth, mold, or soft, mushy spots indicate fungal infection or rot. Transplants should exhibit green, healthy foliage and possess a well-developed root system that appears white or light tan. The roots should be free of shriveling or desiccation.
For transplants, yellowing or floppy leaves may indicate stress from shipping or improper handling, though slightly bent leaves are often normal. A healthy transplant should stand upright and have a pencil-thick neck. If the starts cannot be planted immediately, store them in a cool, dark, and dry location with good air circulation to maintain dormancy and prevent premature sprouting.