Onions are a popular and rewarding crop for home gardeners, offering a versatile ingredient that stores well. Successful cultivation depends heavily on timing and varietal selection specific to the Midwestern climate. This guide focuses on the precise steps Nebraska gardeners should follow, from choosing the right type of onion to the final harvest and curing process.
Selecting the Best Onion Varieties for Nebraska
Onion varieties are classified by the number of daylight hours required to trigger bulb formation. Since Nebraska is in the northern growing region, gardeners must choose long-day varieties for proper bulb development. These onions require 14 or more hours of daylight to begin forming bulbs, allowing time for foliage growth before the summer solstice. Planting a short-day variety causes bulbing too early, resulting in small bulbs. Each leaf an onion grows translates into one ring layer in the mature bulb, making robust early growth important. Suitable long-day examples include the sweet ‘Walla Walla,’ ‘White Sweet Spanish,’ and ‘Utah Yellow Sweet Spanish.’
Precise Planting Schedule for Seeds, Sets, and Transplants
The optimal planting window in Nebraska is early spring. Onions are a cool-season crop that tolerates light frost once established. Planting early allows them to develop strong root systems and green tops before summer heat signals bulbing. This early start is typically four to six weeks before the last expected spring frost, meaning late March or early April, as soon as the soil is workable.
Starting onions from seed offers the widest variety selection but requires sowing seeds indoors in late January or February. These grass-like seedlings are transplanted outdoors once the soil is workable and daytime temperatures reach 50°F.
Transplants, which are nursery-purchased seedlings, are ideal because they provide a significant head start, resulting in the largest bulbs. They should be set out during the same early spring window after being hardened off.
Onion sets (small, dormant bulbs) are the easiest to plant but are prone to “bolting,” which halts bulb enlargement. If using sets, plant them as soon as the soil is workable, pressing them in until the tip is just covered. For large, mature storage onions, growing from seeds or transplants is recommended.
Essential Soil Preparation and Spacing Guidelines
Successful onion growth requires loose, well-draining soil; bulbs struggle in heavy, compacted conditions. Amending the soil with organic matter, such as aged manure or compost, ensures proper drainage and aeration. The soil pH should be slightly acidic to neutral, ideally between 6.0 and 7.0.
Onions are heavy feeders and benefit from a balanced fertilizer incorporated before planting. Nitrogen is important early in the season to fuel the leaf growth that determines the final bulb size. Transplants and sets should be spaced four to six inches apart for bulb expansion. Plant shallowly, only covering the base of the root, as much of the mature bulb forms above the soil line.
Knowing When and How to Harvest Onions
The end of the growing season is signaled when the plant finishes transferring energy from its foliage to the bulb. Onions are ready for harvest when about two-thirds of their green tops have naturally yellowed, dried, and fallen over. This process typically occurs in late July or August in Nebraska, approximately 100 to 120 days after planting.
Once the tops have flopped, withhold both water and fertilizer for about a week to encourage the final maturation process. The bulbs should be carefully lifted from the ground, avoiding bruising, which can lead to storage rot.
Curing is necessary for long-term storage. This involves drying the onions in a warm, shaded, well-ventilated area for several days to a few weeks. Curing is complete when the necks are completely dry and papery, and the outer skins are tight, preparing them for winter storage.