Sowing The Seed
Onions are best started indoors, 8 to 12 weeks prior to the last frost. In some Northern regions, it may be best to even begin sowing in the month of December. Having said that, sow your black onion seeds directly to the surface of the soil. Cover with a quarter inch of topsoil. Transplant early bulbs into the garden when the weather is warm enough to work the soil.
Growing Conditions
Onions are a cool weather crop, so they thrive in the early months of Spring and the late months of Fall. Ideal temperatures should stay beneath 70F, but above 55F. You will also want to provide an area of full sunlight for the majority of the day. The soil should be friable, fertile, as well as loose and free of all rocks or gravel. You will also want to make sure that your sowing medium is well drained as well. To increase drainage, we recommend adding a light compost to areas containing hard, compact soil. Water the seeds daily so that the soil remains moist, but avoid drowning or overwatering.
Germination & Growth
Onions typically begin germinating in about 7 to 14 days after sowing. The green tops will grow to roughly 20 to 24 inches tall, producing 8 to 12 ounce bulbs. Onions can be spaced roughly 3 to 4 inches apart from one another, in rows spaced 12 to 18 inches apart. The tops can be used in soups, on salads and in casseroles as well. The onions themselves are enjoyed raw on burgers & sandwiches, cooked in stir fry, or added to a freshly made pizza.
White Sweet Spanish Onions can be harvested in roughly 110 days. You will know when its time to pull them up because the tops start to lose their coloring and flop over. It may be best to loosen the soil around the bulb, prior to pulling them up. Once the onions are out of the ground, let them sit in the sun for a day to dry them out.
We recommend that you choose a sunny and dry day to harvest your onions.