A Vegetable Gardener’s Dream Plant – Onions
By Jim Binnings, CCMGA Certified Master Gardener
When selecting which vegetables to grow in your garden, there are a lot of choices, but few vegetables rise to the lofty heights of the onion. I am tearing up just thinking about all the possibilities…haha. If you are a vegetable gardener, onions should be in your garden every year. Not many vegetables can add flavor to a dish the way onions can. Not only are they tasty, they are super easy to grow, they can be grown as an annual (bulb onion) or a perennial (bunching onion), and onions are relatively pest and disease free. And something about onions I have learned to appreciate is that they are a natural pest repellant. Rabbits and insects do not like the smell of onions. I have started growing onions and garlic around the outside edges of my vegetable bed for this purpose. And because of this, onions make great companion plants. Additionally, they are surprisingly healthy to eat. Onions are a good source of vitamin C, B6, biotin, chromium, and dietary fiber. Studies have also shown that onions lower blood sugar. In this article, I am going to discuss growing bulb onions and then move on to their cousin, the bunching onion.
BULB ONIONS
Bulb onions are part of the Amaryllidaceae family, along with garlic, leeks, and chives. Bulb onions are going to be red, white, or yellow. They are either American onions, which have a strong flavor, or they will be European onions, which have a milder flavor. Bulb onions can be started from seed in the fall or onion plants in January. Most gardeners find it easier to grow onions from onion plants. Typically, gardeners buy “sets” of onions to plant. A set usually contains 50 or so plants. In North Texas, we can only grow what are known as short-day or intermediate-day onions. This refers to the number of hours of daylight the onion needs to grow successfully. Short-day onions will bulb with 10-12 hours of daylight. Intermediate day onions need 12-14 hours of daylight, and long day onions need 14-16 hours of daylight to bulb.
Onions grow best in raised beds because the fruit is a tuber and grows under the soil. Bulb onions need a depth of four to five inches at maturity. Whether in a raised bed or in the ground, make sure the soil is not compacted so the bulb can grow easily. Onions are heavy feeders, so for the best results at planting time, mix a phosphorus-heavy fertilizer into the soil an inch or so below the seed to give the bulb a boost in the beginning. Then, once the onions start growing, apply a nitrogen-heavy fertilizer every month or so. Stop fertilizing once the onion starts to bulb and the neck of the plant starts to feel soft. This is usually sometime in mid-April.
If you are going to start onions from seed, put them in the ground mid to late October in north Texas. Sow the seeds about ¼ inch into the soil. They should sprout within a week or two. Around February, when the onions have started growing the plants will need to be thinned. Leave around four to six inches between plants. Any pulled onions can be transplanted in other parts of the garden or eaten as scallions.
If you are starting transplants (sets), you should plant the onions mid to late January. I usually start visiting my local nursery in the middle of January, looking for sets. If the sets you see look dry, don’t worry too much. The plants will live on the nutrients in the bulb for several weeks. But do get them in the ground as soon as possible. Each plant should be put in one inch deep, and the more space between onions, the bigger they will get since the plants will be competing for soil nutrients. As mentioned earlier, onions are heavy feeders, so “DO” add a nitrogen-heavy fertilizer once a month during the growing season. I admit I have not done this in the past, but I will start this year…..I learned something new today.
I can say that I have been growing onions for years and have never had any problems with disease or pests. But to avoid blight or purple blotch, just make sure the onions aren’t growing in soggy soil for long stretches of time. Onions need to be grown in well-drained soil to be disease-free. The main pest is the onion thrip. They will nibble on the leaves and suck the juices out of the plant. If a pest problem is causing noticeable damage to the leaves and bulb, in my opinion, the best thing to do is pull the onion and throw it away to keep the pests from spreading to other plants. The literature I have read mentioned a few chemical and biological treatments for pests, such as thrips. I would be VERY careful and read all labels and research the proper use of “vegetable gardening” safe chemicals since you are growing onions to eat.
Have you seen a bulb onion flower? What is up with that?
Last year I had several onions bolt in April and flower. The main reason bulb onions flower is because of fluctuating temperatures. The plant is tricked into thinking it is at the end of its life cycle. When flowering happens, just pull the onion and enjoy it in your favorite dish (an onion that has flowered will not store well). Or you can leave it blooming for the pollinators to have a meal or two. Either way, at this point, the onion has quit developing its bulb.
When do you harvest onions?
Onions should be ready to harvest sometime in May. I usually wait for the leaves to start falling over. But for sure, look at the soil level, and when the onions are ready, you will see the “shoulder” of the bulb above the soil level.
How do you cure and store onions?
Once the onions have been harvested, they need to be cured, and then they can be stored for later use. To cure onions, put them in a dry, shady spot that gets good airflow. Do not cut the tops (leaves) off yet. The idea here is to let the onions dry out. This will take several weeks. When the leaves are dry, and the outer layer of the onion is crinkly, the onion is ready for storage. At this point, cut the leaves off one inch above the onion bulb and store it in a dry, shady spot. Cured onions can be stored for months.
Now that I have got you thinking about adding bulb onions to your garden, what are the varieties to grow in north Texas?
Here is a list short day onions which the Texas Master Gardeners recommend as of 2020.
Short day red onions: Red Bone, Sakata Red, Red Burgandy, Red Hunter, and Red Granex. Short day white onions: Cirrus, Marquesa, TX Early White, Crystal Wax, and Sierra Blanca.
Short day yellow onions: Chula Vista, Cougar, Early Grano 502, Granex, Jaguar, Legend, Linda Vista, Mercedes, Prowler, Safari, and TX1015Y. Make note of this last onion… TX1015Y. I have read recently that this onion has been added to the “Texas Superstar” list of plants. If you like sweet onions and want to improve your odds of a good harvest, give 1015Y a try.
BUNCHING ONIONS
I think any discussion on growing onions should include growing the cousin of the bulb onion and the bunching onion (Allium fistulosum). Bunching onions are very versatile and really should have a spot in every garden. Three characteristics separate the bunching onion from the bulb onion. First, they don’t produce a bulb. Each plant will put up a half to a dozen shoots. The shoots resemble the bulb onion leaf. The shoots have green leafy uppers and white bases. Second, bunching onions are perennial plants in zones that don’t see many freezes in a year. And third, bunching onions are considered a “cut and come again” plant. This means you can cut the shoots, and the shoots will grow back fairly quickly.
Bunching onions are a compact plant that can be grown in an area as small as five inches. They prefer full sun but will tolerate some shade. They grow best in well-drained soil. Adding good quality compost during the growing season is all the fertilizer they need.
To start from seed, work the soil until it is loose and well-drained. Put seeds in the ground during the spring (April). Put the seeds ¼ to ½ inch deep every inch or so. If starting from transplants, put the plants into the ground in May. Take the transplant, cut the roots back to ½ inch, and cut the tops (leaves) to around four inches. Put some good quality compost in the hole along with the plant. Space the plants every inch or so.
For the first month or two, cut any flowers that appear so the plant's energy can go into developing a healthier root system. After that, bunching onions requires very little attention other than keeping the area around the plants weed-free. If you plan on keeping the onions as a perennial, add quality compost several times a year.
Bunching onions can be harvested within 60 days of germination. Once the plants are around eight inches tall, you can cut the shoots almost down to the ground, and they will grow back. You can also harvest the whole plant by working a fork into the ground and pulling up the whole plant. Bunching onions don’t keep well, so they are best eaten right away.
Like their cousin, the bulb onion, bunching onions are relatively disease and pest free. To avoid rot, keep the plants in well-drained soil. Keep an eye out for aphids, snails, and pill bugs when the plants are young. Many gardeners recommend taking older bunching onion leaves and making a soapy solution to spray on younger plants to deter aphids. Because bunching onions and their cousin, the bulb onion, have a strong odor, they will deter and confuse insects and pests. This makes onions a great companion plant. Mixing onions in with other vegetables is a wonderful idea. Onions are great companion plants for tomatoes, peppers, and eggplants. They also are good companions for leafy green vegetables.
What’s not to like about onions……….ok their taste can be strong 😊.
Onions are easy to grow, healthy to eat, great to cook with, can be grown in that tight little spot we all have in our beds, and are good companion plants. As a vegetable gardener, any discussion of what to grow needs to include onions. It's January, as you read this article, and the local nurseries are planning to make room for the delivery of bulb onion transplant sets. In a few weeks, it will be time to plant bulb onion transplants. Then, in April, it will be time to start bunching onions from seed. And then in May it will be time to plant transplant bunching onions. If you plant onions every year, you know what time it is. If you haven’t grown onions before, it is time to start the new year with a new vegetable in your garden.
References:
https://aggie-hort.tamu.edu/plantanswers/publications/onions/ONIONGRO.html
https://thedallasgarden.com/growing-onions-in-north-texas-the-ultimate-guide/
https://agrilifetoday.tamu.edu/2021/11/24/texas-super-sweet-onion-named-latest-texas-superstar/
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