There once was a time when most East Texans had large garden patches to grow food for the table. That isn't true anymore since most of us live in more crowded urban areas with smaller and often tree-shaded lots. But interest in growing produce is high again, with many wanting at least small garden plots in raised beds or containers.
My dad loves onions with every meal, so I always try to grow him some. And we all know about Noonday and the history of sweet onion production there. Today, we'll look at successfully growing onions in containers, but the information certainly applies to raised beds and even traditional garden rows.
When growing onions in containers, there are several key factors to consider. The first would be the container to grow them in. Regardless of the container, adequate drainage is a key to success. A soilless mix that drains rapidly should be used. Ideally, when watering a container-grown plant, water should soon come out of the bottom of the container. This not only indicates proper drainage, but also enables leaching of fertilizer salts which, if accumulated in heavy concentrations, can damage a plant's roots.
Soilless mixes contain no dirt from your yard or garden. No matter how wonderful you think your soil is, when soil is put into a container, it loses many of its beneficial qualities. Soil in a container compacts, causing poor drainage and insufficient aeration. Microorganisms such as nematodes and pathogenic fungi may also contaminate the root system if non-pasteurized soil is used. Many suitable types of soilless professional potting mixes are available. A soilless mix should be disease- and weed-free, retain adequate moisture after watering, yet be well-drained and lightweight. Most professional potting soils are a combination of sphagnum peat moss, vermiculite and perlite, with some incorporating composted pine bark for increased drainage and reduced cost.
Once you have formulated or purchased a well-drained soilless mix, be sure the container being used has adequate drainage capabilities. If a water-tight container is being used, drainage holes will have to be drilled. When considering drainage holes, remember, the more the merrier. Also, don't worry about lining the bottom of the container with gravel or broken pots to expedite drainage. Recent research indicates that doing so actually impedes drainage.
Half whiskey barrels or something of a similar size makes a great container for onions and other vegetables. My uncle uses used cattle feed supplement containers. At SFA, we used 30-gallon nursery pots. And back at the farm, I used to use homemade crown-tire planters made from my worn-out truck tires but now use galvanized fire rings. As long as the container is large enough, has good drainage and contains a well-drained potting soil, it will work.
If you don't plant the onion varieties best suited for East Texas, you are doomed before you begin. Onion bulbs form when the carbohydrates in the foliage are transferred to the bulb. The triggering of this transfer is dependent upon day length and temperature and not the size or age of the plants. There are different types of onion varieties categorized on which day lengths they produce foliage. Here we grow short-day onions, which bulb when the days start to get longer in the spring. This means the earlier you plant them, the longer they have to produce foliage before bulbing.
The short-day onions that do well here, and are traditionally grown here, were all bred in Texas. These include Grano 502, Granex ("Vidalia" or "Noonday") and 1015Y (Texas Super Sweet). These can generally be found at local feed stores or ordered directly from Dixondale Farms in Carrizo Springs, where most of the onion transplants in the United States are grown (www.dixondalefarms.com).
After selecting the best variety, you will want to plant them about knuckle deep, 4 inches apart if you want them to mature as is, or two inches apart if you want to gradually harvest every other one as green onions. They should be watered in immediately after planting with a half strength water soluble fertilizer. Always remember, the earlier you plant them, the larger the bulbs will be, because day length causes everybody's onions to start bulbing on the same day.
Onion plants require high levels of slow-release fertility for vigorous, continuous growth and high yields. When I was a kid, I was told not to fertilize onions too much or they would make "all tops and no bottoms." That was wrong. Always remember the more onion top you grow, the larger your onion bulb will be. Every onion bulb is composed of modified leaf tissue. So for every leaf you produce, you create another ring in your onion. Soilless mixes are lacking in sufficient nutrients for optimum production. Fertility can be provided in two ways. The most common technique is to periodically water with a fertilizer solution. Commercially prepared, water-soluble formulations are available in local nurseries and garden centers. Follow label directions when mixing.
Retired Texas AgriLife Extension Vegetable Specialist Dr. Jerry Parsons in San Antonio recommends a slow release fertilizer like Osmocote in addition to regular feedings with a water-soluble fertilizer (the stuff that usually turns the water blue or green). Dr. Parsons uses four times the recommended rate on the slow- release fertilizer since onions are such heavy feeders and this slow-release fertilizer only releases a small amount at a time. Their benefit is that they don't burn the plants yet constantly feed them. If you choose to use a typical quick release granular lawn fertilizer like 15-5-10, you must be very careful to only sprinkle tiny amounts every several weeks to make sure it doesn't burn the roots of the young plants. Always remember fertilizers are salts and can easily damage plant tissue. You should always water the plants immediately after applying a quick release fertilizer to make sure it's washed off the foliage and stem.
Onions are edible at any stage of the game, but for the most production and the best storage potential, wait and harvest them after the bulbs have fully expanded and the tops have fallen over, generally around May.
Greg Grant is the Smith County horticulturist for the Texas A&M AgriLife Extension Service. You can follow him on Facebook at Greg Grant Gardens, read his "Greg's Ramblings" blog at arborgate.com or read his "In Greg's Garden" in each issue of Texas Gardener magazine (texasgardener.com).