Onions For Beginners
Onions are a wonderful addition to your garden! They take up minimal space, are easy to plant and maintain, and can store all winter.
They also pair well with other produce in your garden. Use them in sauces, salsas, and salads. (Say that five times fast). Or if you’re like me, a throw thick slice on the grill to pile onto your burger.
Being a root vegetable, they can be planted early in the season, which helps satisfy my need to get my hands in the dirt before the soil is ready for things like tomatoes.
The first question you need to answer before you start, is what type of onion you want to grow. I usually do mostly yellow onions for their versatility in recipes, and a handful of red onions for some of my favorite summer time dishes.
Make sure to take note of the “storing time” of specific varieties. Some are better for eating fresh and can only be stored for about a month, whereas others can be stored for 4-5 months!
Here’s a good list of some different varieties, but your local garden center should have good information for you as well. Click here for an article from Gardener’s Path.
Key Points:
- Onions are a cool weather crop that can be planted when soil temperatures reach 50 degrees F.
- Plant 1/4 – 1/2 inch deep, 3-4 inches apart, in rows 12-18 inches apart
- Water once a week if rain is inadequate.
- Harvest when the tops start to die and tip over.
- Cure before storing to promote longevity and prevent rot.
- Onions can deter aphids, so plant with your lettuce.
Onion Seeds, Onion Sets, or Onion Plants? What’s The Difference?
Apart from variety, you also should note there are three ways you can buy your onions: seeds, sets, and plants.
Onion Seeds
This one is the most obvious. You can buy your onions in a seed packet to sow into the dirt. This is the most cost effective way to grow your onions.
It’s a bit more work doing it this way because once your onions sprout you will have to thin them out. And they will take longer to form bulbs than the other options.
Seeds are also a good option to start indoors or in a greenhouse before the ground thaws.
Onion Sets
This is probably the most common way to grow your onions. Onion sets have been grown from seeds the previous season, and were harvested as immature bulbs. They sit dormant over winter and can be planted the following spring to be grown into full sized onions.
The nice thing about onion sets is that they are easy to plant and space out so you don’t have to worry about thinning later on.
Sets are typically sold by the pound, or in bags.
You can also grow your own sets each year to be used for the following year. This can save some money. I like this article from Harvest to Table on how to do it yourself.
Onion Plants
Plants are my favorite way to grow onions. They are plants that have been started this season. You can buy them by the bunch and will have green sprouts shooting out the top.
Plants are sown exactly the same as onion sets, and also won’t need to be thinned out.
The reason they are my favorite is that they tend to be more successful. I’ve struggled with my onion sets forming mature bulbs in the past, but haven’t had that problem with plants. We grow beautiful, full onions every time when we start with plants.
Planting Your Onions
Onions are relatively easy to grow. They don’t require a large amount of space or anything special to get them going. Just good drainage, plenty of water, and full sun.
Prepping Your Soil
As with anything, soil prep is important. Onions like loose soil with good drainage, high in organic matter, with a slightly acidic pH.
We are constantly adding organic material and manure from our chicken coop to our soil to continue to build it up. You can also add compost directly to the area you intend to plant your onions for a nutrient boost.
This was taken from the U of M website. Article found here.
- Onions grow best in well-drained soil with pH between 6.0 and 7.0, and high organic matter.
- Apply phosphorus (P) and potassium (K) according to soil test recommendations. Many Minnesota soils have enough phosphorus.
- Unless your soil test report specifically recommends additional phosphorus, use a low- or no-phosphorus fertilizer.
- You can increase your soil’s organic matter content by adding well-rotted manure or compost in spring or fall. Do not use fresh manure as it may contain harmful bacteria and may increase weed problems.
- Onions require a good supply of available nitrogen, but too much nitrogen can result in late maturity, large necks that are difficult to cure, soft bulbs, green flesh and poor storage quality.
- Side dress with fertilizer after root systems are well-developed.
- Do this once or twice during the growing season, with urea (45-0-0) at a rate of 0.25 to 0.5 pound per 25 feet of row.
- Spread the fertilizer alongside the row of onions, about six inches away from the plants, and scratch it into the soil.
- Do not use “Weed and Feed” type fertilizers on vegetables. They contain weed killers that will kill vegetable plants.
Sow Your Seeds (or sets…or plants)
Seeds
You can sow your seeds early in the spring, as soon as the soil is workable.
- Sow seeds in a 2 inch wide band
- 1/4 to 1/2 inch deep
- Rows should be spaced 12 to 18 inches apart
- Once sprouted, thin to 3 – 4 inches apart
Always check your seed packets for variety specific variations to this.
Sets and Plants
Onion sets and transplants can be treated basically the same when planting. They can tolerate a mild frost and can put put in the ground when soil temperature reaches 50 degrees (F). In Minnesota (zone 4b), that is typically some time in April or early May.
You’ll want to trim the roots of your plants to roughly 2 inches, and the tops to roughly 4 inches.
Your sets should be planted with the pointy tip up.
- Create a furrow in your soil with a hoe
- Place onions 2 inches deep
- 3 to 4 inches apart
- In rows 12 to 16 inches apart
Caring for Onions
Onions are shallow root vegetables that require a lot of water for good growth. They need a good soaking once a week (more if soil is sandy), so monitor rainfall and water accordingly.
Onions can be hoed between rows to control weeds, but avoid going too deep. You can cover your rows with organic material to reduce the amount of weeding and cultivating you are doing. Grass clippings and straw are good options, but make sure your material is weed free or it will defeat the purpose.
This year we are trying pine shavings because we had them on hand. Be mindful of your soil pH though as pine shavings will increase the acidity. I’m not worried about this with my onions as they like a bit of acidity, but I wouldn’t add it all over my garden. I’ll let you know how it works out this season!
Harvesting and Storing
You can start harvesting your onions when the tops start falling over or turning brown. This means the plant is mature and has stopped growing, which usually happens in late summer or early fall.
We usually pull some earlier that look like they have a good bulb on them for use as needed through the summer, but wait to do a mass harvest until the majority of them show they are ready.
It’s okay to leave them in the ground for a while after they have matured, but pay attention to rain. You don’t want them sitting in wet dirt for too long after they are done growing.
To harvest, wait for a dry sunny day. You can often just gently tug on the bulb (don’t yank on the leaves) and they’ll come right out. If they’re a bit tough, use a garden fork or shovel to wiggle around the outside (careful not to touch or damage the onion). This should loosen the soil enough to make pulling them much easier. Leave the tops on – cutting will leave the onion vulnerable to bacteria during the curing process.
Curing Your Onions
Once you’ve pulled them all out, let them lay on top of the soil, or any other sunny spot of your choice for a day or two. This will let the roots dry out.
The next step of the curing process is to find a shady spot (to avoid sunburn) outdoors, or a garage or basement if it rains a lot and you can’t keep them covered. You want to lay them out without crowding them so they get plenty of air flow. You want your onions to dry, dry, dry. Moisture will cause them to rot quicker and they won’t store nearly as long over winter.
This process should take two to three weeks to fully dry your onions.
Once cured, the roots and tops should be very dry and wiry. The skins should be papery and the outer layer should flake off easily.
To store them, you can decide if you’d like to cut the tops off at this point and remove the outermost layer leaving a nice clean looking onion for storage. Otherwise you can leave the stems intact and braid them together. With this method you can hang them in your cellar or pantry for storage. Braiding is going to give you continued airflow and might increase their shelf life, but both options are good.
Properly curing your onions can make them last for many months. We’ve never had our onions last us until Spring, but only because we eat them up way too quickly. The longest we’ve had onions in our basement is February, but they were still very fresh and no signs of rot.
Companion Plants For Onions
Onions do a good job of repelling a lot of insects due to its potent smell. They are great companions of anything in the cabbage family like broccoli, kale, kohlrabi, and brussel sprouts because they deter cabbage worms.
They also repel aphids and Japanese beetles making them a good friend to your veggies typically hit by those such as lettuce, tomatoes and strawberries.
Other good companion plants: carrots, dill, beets, peppers
Avoid
You want to keep them away from peas, beans and asparagus for possible flavor contamination. And avoid planting with others in the onion family like shallots or leeks because of the potential to spread onion maggot.
I hope this helps you get started on your veggie garden! Let me know if you have any questions or more tips to grow onions, or what you’d like help with next.
If you’re local in Southern MN check out our Farm Stand to see what’s growing.
