Now is the time to get onions in the ground
By Tracey Payton Miller
OSU Extension Horticulturist
I rarely make a dish without onions, so having them on hand and homegrown is a bonus in my opinion. I grow at least a set of onions every year in the garden. But now is the time to get those onions in the ground, so you can enjoy them this summer.
Around Valentine's Day is the best time to plant onion sets or bulbs in the garden. But there may be some confusion on just what types to plant. There is an abundance of onion varieties available in any garden center, but not all do well in Oklahoma. In general, red onions and "long-day" onions don't do well here. I recommend you only plant those onions termed "short-day" varieties.
Many plants may be considered short-day or long-day plants. Short-day plants flower when the days are shorter than 12 hours, like fall and winter. Short-day plants include poinsettias and mums. Long-day plants flower when the days are longer. Long-day plants include many summer flowering plants such as coneflowers and summer vegetable crops. Day-neutral plants will flower regardless of day length. Short-day onion varieties that do well here include: Texas 1015 (aka Grano 1015Y), Granex, Yellow Sweet Spanish, Walla-Walla, Crystal Wax, White Sweet Spanish, and Evergreen White. I really like Texas 1015, as they are sweet wherever grown and readily available.
Bulb or tuber forming vegetables benefit from a fluffy soil, free of rocks or clods which can deform the crop. Clear the soil of any debris or cover crop prior to planting. Space the onions 4 to 5 inches apart and roughly 1 inch deep. Lightly shower the onions with water immediately after planting, taking care to not wash them out. A soaker hose can be laid before or after planting, and set with a timer for ease of watering. One or two weeks later, apply a nitrogen fertilizer and 1 to 2 inches of straw or cottonseed mulch. I recommend a nitrogen fertilizer, as most garden soils I've seen are tragically high in phosphorus and potassium. You may reapply this fertilizer monthly. I like to use blood meal as a fertilizer because it's organic and has a low percentage of nitrogen that won't burn the plants. Each onion leaf directly corresponds to a layer on the bulb. So, for bigger onions, you need more leaves. For more leaves, you need nitrogen.
Harvest onions 7 to 10 days after the tops naturally fall over. Then collect the onions and dry them for a week or so. I like to tie my onions together in clumps of five or six, and then hang them from a deck or porch railing. When the green tops are dried, and a skin is formed, the onions are ready for use or storage.