Multiplying onions grow from seed or from dry bulbs, depending on variety. The three major types available include Japanese bunching onions, shallots and potato onions. Japanese bunching onions such as the Evergreen White cultivar start well from seed in early spring. Shallots and potato onions grow from dry sets planted in fall. Dividing clusters of mature bulbs provides planting stock for expanding the onion bed. Bunching onions and shallots yield long-season harvests of green scallions. Shallots and potato onions grow bulbs suitable for dry storage.
Things You'll Need
- Garden tiller
- 10-10-10 fertilizer
Test the soil where you intend to grow multiplying onions and correct the soil's pH balance to between 6.0 and 6.5. Applications of agricultural lime raise the pH and acidic fertilizers lower the pH.
Till the soil deeply with the garden tiller. Work in rotted vegetable matter or finished compost to improve soil quality and soil drainage.
Dig a trench 4 inches deep and 6 inches wide and the length of the proposed onion row. Scatter 1/2 lb. of 10-10-10 fertilizer along the bottom of a 100-foot trench.
Rake soil over the top of the fertilized trench to prepare the site for the onion row. Onions grow feeder roots only 6 inches long and grow best with a band of fertilizer laid below the planting row, according to University of Hawaii Department of Tropical Plant and Soil Sciences.
Plant multiplying onion seed 1/4 inch deep over the fertilized trench, spaced 1 1/2 inches apart. Cover the seed with fine soil.
Cultivate the rows to suppress weeds or weed by hand to reduce competition with the onions in the row.
Apply 1 lb. 10-10-10 fertilizer as a side dressing, five to six weeks after plants emerge. Thin onion plants to 3 inches apart to encourage bulb growth or harvest green onions when stalks reach pencil thickness.
Tips & Warnings
- Yellow-green onion tops indicate a nitrogen deficiency. Apply a third dose of high nitrogen fertilizer three weeks after the first side dressing to encourage healthy top growth.
- Dig onion sets for replanting when the onion tops dry and topple. Divide multiple bulbs and replant in the fall at a 1-inch depth. Allow 3 to 4 inches between plants.
- Plant shallots or potato onion bulbs in the fall. Plant the bulbs from 1 to 1 1/2 inches deep, measured from bulb tip to ground surface. Space shallots 4 inches apart, and give potato onions 16 inches between plants.
- Harvest shallots as green onions in winter and spring or as dry bulbs the following summer when tops die down.
- Dig potato onions the summer following a fall planting. Replant a mix of large bulbs and small bulbs in any new potato onion row. Large sets produce clusters of small bulbs and small sets produce a single large potato onion bulb.
- Photo Credit Polka Dot Images/Polka Dot/Getty Images
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