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Yard and Garden: Prepare and Plant Onion Cultivars in Spring

By Richard Jauron
Iowa Stare University Extension – Horticulture

With spring here, it’s time to think about planting in home gardens. Onions are a popular garden product, but they do require some special conditions and care to get optimal results. Here are some tips from Iowa State University Extension and Outreach horticulturists on the proper way to plant them.

Onions perform best in well-drained, slightly acidic, fertile soils in full sun. The planting site should receive at least six hours of direct sun each day. Heavy soils can be improved by incorporating organic matter, such as compost, into the soil. Onions require higher fertility levels than most other vegetables. Apply one half to a pound of an all-purpose garden fertilizer, such as 10-10-10, per 50 square feet and till into the soil prior to planting. Four to five weeks after planting, sidedress with additional fertilizer. Sprinkle one pound of an all-purpose garden fertilizer per 100 feet of row. Place the fertilizer in a narrow band about 2 to 3 inches from the base of the onion plants.

Onions may be grown from seeds, sets (small bulbs) and plants. Base your planting method on cost, availability and ease of planting. For most home gardeners, growing onions from seeds is the most difficult planting method as germination rates are sometimes poor. However, it is the least expensive. Seeds of specific onion cultivars are readily available. Growing onions from sets is easy. However, specific onion cultivars are usually not available. Onion sets are typically sold as red, white or yellow onions. Since the cultivar is unknown, the flavor, use and keeping quality of onions grown from sets vary considerably.Growing onions from plants is the preferred planting method for many home gardeners. Onions are easily grown from plants. Additionally, specific cultivars are available at garden centers.

For more information, visit www.extension.iastate.edu or contact the ISU Hortline at (515) 294-3108 or hortline@iastate.edu.