It’s a waste of tears crying over the tasteless onion varieties in your local grocery store when growing onions of your own is so simple. Originally hailing from Pakistan, homegrown onions come in a variety of flavors and textures. And, they are a staple ingredient in flavorful dishes from around the world.
Your homemade stir-fries and soups will never taste the same once you incorporate freshly grown onions into the mix. Onions are easy to grow, simple to store and take up so little space that you can sneak some into the edges of your flower beds for a bonus harvest.
Whether you decide to grow your onions from seeds or starts is up to you. Either way, you will be well rewarded for your time spent growing this garden delicacy.
- When & Where You Should Grow
- Understanding Seed Germination
- Direct Sowing
- Watering & Mulching
- Companion Planting
- Common Pests & Diseases
- Harvesting & Storing
- Saving Seeds
- Best Variety for You
Seeds, Transplants or Sets: Start Growing Onions
There are a lot of options when it comes to growing onions. The onion is a biennial plant, which means that its growing life lasts for two years. Additionally, the plant doesn’t produce seeds until its second year. Onions are traditionally grown directly from seed, from transplants or from pre-bought sets that have already made it through their first year of growing.
You will need the longest amount of time to grow onions directly from seed. On the other hand, transplants give you a jump start on growing because you buy them as bunches of live seedlings that are several weeks old. Though they dramatically shorten the growing period, they also are more susceptible to disease than onions you seed yourself. Sets, in contrast, are immature bulbs that you grew the previous year. They are easy to plant and grow quickly. However, they tend to bolt early and come in more limited varieties than seeds or transplants.
When and Where Should You Grow Onions?
Onions grow best in full sun and in fertile, well-drained soil. At the beginning of their growing period they prefer cool weather because all their energy is focused on growing their tops, so be sure to get yours planted in the early spring. The bulbs will start to form as the days get longer and the weather becomes warmer.
In fact, onion bulbs grow in direct response to day length. Long day varieties like the ‘Sweet Spanish‘ need at least 14-16 hours of daylight, while short day varieties like ‘Bermuda‘ can get by with 10-12 hours. The key to onion success is knowing your summer sun conditions and planting the right varieties for your region.
Preparing an Onion Bed
Regardless of what type of onion you choose to grow, your onion bed will need to be filled with fertile, loose soil with good drainage. Stay away from clay soil or amend it well with sand and compost. It’s a good idea to dig through the soil for at least six inches and mix a one-inch layer of compost in the bed directly before planting. Slightly acidic soil (between a 6.2-6.8 pH level) tends to be ideal for onions.
Growing Onions From Seeds
At over four months, your onions will take the longest time to grow when you plant them directly from seed, but the wider choice of varieties to choose from makes this well worth it for many gardeners.
Plant your seeds indoors or in cold frames at least two months before the last frost date. Try to keep the temperatures cool, usually, about 60 degrees F. As your seedlings sprout to several inches tall, you can trim off the ends to encourage them to grow stocky, not spindly (be sure to eat the cuttings in a salad after!)
Direct Sowing Outdoors
You can direct sow your onion seeds about four weeks before the last frost date. Plant your seeds thickly in rows that are over ½ an inch thick. A smart idea is to mix in early-sprouting radish seeds with your onions so that your rows will be marked early on before your onions sprout. Once the seeds have sprouted, thin them out to an inch apart, and to six inches apart once they get several inches tall. If you don’t want to plant in traditional rows, you can “scatter plant” your seeds by fitting them in any extra space at the end of garden beds or along your flowers. Just be sure to remember where they’re planted so you don’t accidentally weed them out!
Growing Onions From Sets
Growing onions from sets couldn’t be easier, so long as you plant the right variety for your climate conditions. Simply plant each set about an inch deep and space them three inches apart. You can harvest sets early for use as green onions or scallions or allow them to grow to maturity for the biggest harvest.
Watering and Mulching Requirements
To grow best, onions need to be well weeded and well moisturized. Use a sharpened hoe to cut off weeds that are close to your onions, being careful not to nick the bulbs in the process. Once your onions are well established, you can lay down a thick mulch to keep the weeds suppressed.
Overly dry conditions can cause your onions to suffer and even split in half. To avoid this, provide them with at least an inch of water a week, keeping in mind that seeds and transplants need more water than sets. A soaker hose or drip irrigation system tends to work well for getting the bulbs hydrated without overly wetting the greens.
If you prepared your garden bed well before planting, there shouldn’t be any reason to have to add fertilizer throughout the growing season unless you are eager to grow massive bulbs. If so, you can add some nitrogen fertilizer to the beds every few weeks.
Companion Planting and Rotation Considerations
Planting onions near other flavorful vegetables tend to benefit both varieties. Many people have reported that chamomile and summer savory taste better when planted near onions, and that carrots, beets, kohlrabi, lettuce and tomatoes all grow well next to onions. For best results, keep your onions far away from peas and asparagus.
Common Pests and Diseases for Onions
Onions don’t tend to have a lot of pest and disease problems, but the ones they have can cause a lot of damage.
- Gophers and other rodents love to dig in onion beds and eat the bulbs, and the best way to keep them away is to use wire animal traps or construct sturdy garden fences around your vegetables.
- Onion Thrips are tiny insects that love to nibble on onion leaves, but you can prevent an invasion through the use of overhead irrigation systems or by introducing their natural predators, like lacewing larva, to your garden.
- Onion maggots live in the soil and enjoy eating the roots of onion seedlings. Rotate your onion beds annually to prevent this from being a problem.
- Downy mildew loves cool, humid weather and can quickly spread a white, powdery fungus to every onion in your bed. You can avoid it by planting in an area with good drainage and not putting your plants too close together.
Harvesting and Storing Onions
Onions are almost ready to harvest once their tops stop growing and begin to turn yellow. At this time you can use the back of a rake to bend the tops over towards the ground, which helps to stop them from growing and instead focuses the plant’s energy towards the maturing bulb instead. After a few days, you can dig up the bulbs and allow them to dry out in the sun, being sure to put the tops of some bulbs over others to prevent them from getting sunburned.
Once the outer onion layers are dry, you can wipe off the excess soil and remove the tops. Be careful not to bruise them, as any cuts or bruising will cause your onions to go bad much more quickly. If this happens, simply chop up the onion and freeze it for use in soups and casseroles in the winter. Your onions should be stored in a cool dry place, where they should last between four months to a year.
Saving Onion Seeds
Because onions are biennial, it will take two years of growing before you can harvest seeds from your crop. Isolate the species that you want to save seeds from by at least a mile from other onions and after the first year of growth select out the best bulbs to store for 3-6 months. Replant these bulbs in early spring and allow the plants to form seed heads. Once these have dried on the plant, you can cut them off and thresh the seeds into a paper bag. When stored in a cool, dry place these seeds should last for a year or two.
Choosing the Best Onion Seeds for Your Conditions
The type of onion you chose to plant depends on the length of your days in the summer, whether or not you want to store them and the varieties that you prefer to eat.
- Long Day varieties mature earlier than other types but only store for a few months before going bad. These are ideal for the Midwest up to Canada.
- Intermediate-day varieties are the main crop grown throughout the country and are ideal in regions from Washington DC to northern Arizona.
- Short Day varieties start bulbing after 10-12 daily hours of sunlight and are usually planted in the south during the winter or early spring months.
Besides day length, there are many factors that affect the variety you will grow. Below are some of the most popular types of onions that are grown by backyard gardeners.
- Yellow Onions: considered an all-purpose onion, these varieties become sweeter the longer the cook and are delicious in casseroles.
- White Onions: these onions have a sharper flavor than yellow ones, though they tend to be more tender. They are ideal in spicy salsas.
- Sweet Onions: sweet onions like Vidalias are less pungent than regular onions and are great on salads or sandwiches.
- Red Onions: these tend to be milder than other onions, making them useful raw.
- Egyptian Onions: unlike other onions, Egyptian onions from bulb clusters at the tip of their stems that can be eaten like chives.
Additional Growing Tips for Organic Onions
There are lots of trade secrets that any experienced gardener can tell you about growing a great crop of onions, but here are some tips to get you started for your first few seasons.
- Keep your onions in weed-free areas as they don’t tend to compete well with them.
- Water your onions regularly and uniformly to encourage proper bulb development.
- Start your seeds early! Many onions need at least 110 days to form bulbs, so start as early in the spring as you can.