An essential kitchen vegetable, onions are arguably the world’s most widely used ingredient. They vary in shape and colour from flattish brown to round pale bulbs but share a common structure, with a papery outer ‘kin and protecting inner layers of pale, crisp flesh. Yellow onions are hot and pungent enough to make your eyes water; Spanish onions are the largest, with brown skin and a mild, sweet flavour; brown onions are a smaller variety of yellow onion with an even more pungent flavour, making them a good all-rounder.
HOW TO GROW
- Choose a type of onion to grow.As with most fruits and vegetables, there are many variations of the onion that are appealing for different reasons. Onions come in three general colors – white, yellow, and red/purple – each with their own distinct taste. Additionally, onions are categorized into two growing types: long-day and short-day. Long-day onions are named such because they begin sprouting when the days between 14-16 hours in length (late spring/summer), while short-day onions begin sprouting when days are between 10-12 hours in length (winter/early spring).
- Long-day onions grow the best in northern states, while short-day onions grow the best in southern states.
- Yellow onions are golden in color and have a slightly sweet flavor, white onions are sharp and a bit tangier than their yellow counterparts, and red onions are violet in color and are often eaten fresh rather than cooked.
- Decide how you will plant the onions.In general, there are two popular ways of growing onions: using either onion sets (bulbs) or using onion seeds. Gardeners tend to prefer planting onion sets, as they are a bit hardier and stand up to poor weather better than onion seeds. However, if you’re able and willing to grow your onions from seeds indoors and transplant them outdoors, you can certainly raise them all on your own from seeds.
- You can choose to grow onions from transplants/cuttings, but this isn’t always successful and is much more difficult to accomplish than just using sets or seeds.
- Visit a local nursery to get recommendations on sets and seeds that grow well in your area.
- Know when to grow.Onions can be tricky to grow if they’re not planted at the right time. If planted in cold weather, they can die off or waste energy in blossoms rather than bulbs in the spring. If you’re planting seeds, start them indoors at least 6 weeks prior to planting outdoors. Onions can be planted outdoors at the end of March or beginning of April, or whenever temperatures do not drop below 20 °F (−7 °C).
- Select the ideal location.Onions aren’t too terribly picky when it comes to growing conditions, but they do have some preferences. Select a place with plenty of room and full sunlight. Onions will grow quite large if they’re given enough space, so keep in mind that the more area you give them to grow, the larger they will get. Avoid planting them in a location that is shaded by larger plants or trees.
- Onions grow well in raised beds, so if you’re unable to find adequate garden space, you can build a separate raised bed for your onion crop
- Prepare the soil.Although it takes some forethought, if you are able to prepare the soil of your plot for planting several months in advance, you’ll receive a better onion crop down the line. If you’re able, begin tilling the soil and adding in manure in the fall. If your soil is very rocky, sandy, or has lots of clay, mix in some potting soil to help even things out. Additionally, test the pH level of your soil and add in any necessary compounds in order to create a pH that falls between 6-7.5.
- Testing and altering the pH of your soil is best done at least a month prior to planting, so that any additives have time to take effect on the soil and prepare the foundation for the onions to grow.
- .Get the soil ready.When you’re ready to plant, till the soil about 6 inches (15.2 cm) deep and add a layer (1 cup per 20 feet) of phosphorous fertilizer. Using a mixture such as 10-20-10 or 0-20-0 will provide an extra boost for your developing onions. At this point, be sure to remove any weeds that may be present in the garden plot you’re planting in.
- Dig the holes.Plant onions so that no more than one inch of soil is placed above the sets or seedlings; if too much of the bulb is buried, the growth of the onion will be reduced and constricted. Space onion sets 4–6 inches (10.2–15.2 cm) apart, and onion seeds 1–2 inches (2.5–5.1 cm) apart. As your onions begin to grow, you can transplant them and space them further apart in order to increase their growing size.
- Plant the onions.Place your seeds in the holes you’ve dug, covering them with ½ to 1 inch (2.5 cm) of soil. Use your hands or shoes to firmly tamp the soil over the top of the onions; they grow better in firm, rather than loose, soil. Finish up planting by adding a bit of water, and you’re set to watch them grow!
- Transplanted onions require more water than sets or seeds, so give yours a little extra moisture if that’s what you planted
- Maintain your onion patch.Onions are relatively delicate plants, as they have a fragile root system that can easily be damaged or abused by weeds and tugging. Use a hoe to cut off the tops of any weeds that emerge, rather than pulling them out; tugging the weeds could tug out the roots of the onions, and make growing difficult. Give your onions about 1 inch (2.5 cm) of water per week, and supplement with a nitrogen fertilizer once a month for nutrients. One month after planting, add a layer of mulch between each plant to lock in moisture and block out weeds.
- If you want your onions to taste a bit sweeter, give them more water than you normally would.
- If any of your onions flower, pull them out. These onions have ‘bolted’ and won’t continue to grow in size or flavor.
- Harvest your onions.Onions are fully ripe when the tops appear golden yellow; at this point, bend the tops so that they lay flat on the ground. Doing this will move further nutrients towards developing the bulb rather than growing the shoots. After 24 hours, the tops should appear brown and the onions are ready to be pulled. Remove them from the soil and trim off the shoots at 1 inch (2.5 cm) above the bulb and the roots. Leave the onions to dry out for a day or two in the sun, and then move them to a dry space indoors for 2-4 weeks to continue drying.
- Store onions in stockings or over a wire screen to allow good airflow when drying. This will help them to keep for longer and maintain their flavor.
- Sweet onions will go bad earliest because of their high moisture content, so eat them first in order to prevent rot from making an appearance.
- Discard, or cut up and use, any onions that show signs of decay so they don’t spread disease to other onions in storage.
- Fertilize every few weeks with nitrogen to get big bulbs. Cease fertilizing when the onions push the soil away and the bulbing process has started. Do not put the soil back around the onions; the bulb needs to emerge above the soil.
- Generally, onions do not need consistent watering if mulch is used. About one inch of water per week (including rain water) is sufficient. If you want sweeter onions, water more.
- Onions will look healthy even if they are bone dry, be sure to water during drought conditions.
- Make sure soil is well-drained. Mulch will help retain moisture and stifle weeds.
- Cut or pull any onions that send up flower stalks; this means that the onions have “bolted” and are done.
- To control thrips—tiny insects about as fat as a sewing needle—take a dark piece of paper into the garden and knock the onion tops against it; if thrips are present, you will spot their tan-colored bodies on the paper. A couple of treatments with insecticidal soap kills them. Follow the package directions. Spray the plants twice, three days apart, and the thrips should disappear.
- Onion Maggots: Cover your emerging onion crop with a fine mesh netting. Seal it by mounding soil around the edges. The onion maggot likes to lay its eggs at the base of plants, so the netting should prevent that. You should also keep mulch away because the insects like decaying organic matter, and make sure you completely harvest your onions as the season progresses. Onion maggots are usually a problem in very rainy periods, so these precautions may be unnecessary if you have a dry season.
- Onions are excellent sources of vitamin C, sulphuric compounds, flavonoids and phytochemicals.Phytochemicals, or phytonutrients, are naturally occurring compounds in fruits and vegetables that are able to react with the human body to trigger healthy reactions. Flavonoids are responsible for pigments in many fruits and vegetables. Studies have shown that they may help reduce the risk of Parkinson’s disease, cardiovascular disease and stroke.