How to Start Onions from Seed II

Planted Onions

Once you have started your onions from seeds and once you have your transplants strong and healthy, it’s time to move your onion plants to the garden. If your climate conditions allow, you may choose to put the transplants in the ground early (not to mention that people living in very warm climates may start the seeds directly in the ground). Typically, however, you will need to wait till mid-May to plant your onions in the garden. By that time, they should be about half the size of a pencil.

Onions need soils that’s very hight in organic matter. It doesn’t matter whether you start them in the garden from transplants, sets or directly from seeds: you will need to provide soil high in organic matter. Another thing onions require is well-drained soil. They should not stay in water after a rain, for example.

Onions thrive in a fertile, loose loam. The ideal pH values are 6 to 6.5. It’s also important to work in a 5-10-5 fertilizer or an organic fertilizer to help your onions grow and become strong.

The transplants should be planted about 1/2 inch deep, 4-6 inches apart. In case of larger varieties (producing larger bulbs), place them 6 inches apart. In case of smaller ones, 4 inches is enough.

When they are in the ground, cut the top-heavy leaves back to about 6 inches. It will prevent the heavy tops and it will give the plant more energy to grow the bulb instead of leaves. You can do this thinning of leaves as the summer progresses. Remember, you can use leaves in the kitchen, so don’t throw them away. They are great for salads and cooking.

You may plant single or double rows of onions, depending on your space and preferences. Planting in rows (as the opposite of beds) is great because it requires less work – rows are much easier to weed. It’s important to keep the onions well weeded because otherwise the onions will compete with weeds for resources (light, water, and nutrients). To avoid damaging the delicate and shallow onion roots, make sure to pull weeds by hand.

Planted Onions

To make your onions thrive, make sure to provide them with water and nutrients. Keep the soil surface evenly moist. They should receive at least 1 inch of water per week. They should have a constant supply of moisture during the bulb-enlarging stage. In case the soil is too dry it will put the plants under stress, and it will result in smaller bulbs with a stronger flavor. In case you experience a dry season, you should mulch the onions with grass clippings or leaves. However, make sure to keep the mulch away from bulbs to prevent rotting and diseases. Also, as your onions grow and mature, make sure to brush the soil away from their bases. It’s important that each onion plant perches on top of the ground.

Remember that onions are heavy feeders. You should feed them during planting, but they will sure benefit from fertilizing when the bulbs begin to swell. Another thing you may introduce is a bit of a side dressing of manure. Onions need adequate doses of potassium or else their necks will thicken, so the bulbs won’t store well.

When the onions start to mature, you should ease up on water and fertilizer. This will encourage dormancy. Also, as the onions mature, you should pull the soil away from most of the bulbs. Leave only the roots and the lowest part of the bulb in the dirt. It should look like the onions are sitting on top of the soil. It’s important to do this to encourage the drying process by keeping the soil away from the onion skin. Also, to get the best and healthiest bulbs, rotate the crop yearly.

When it comes to pests, keep an eye on any potential pest problem. Onion maggots are a frequent problem so to avoid them, don’t plant too early in the spring. Also, you may consider using row covers to prevent the egg-laying flies. Other than this, onions tend to be pest and disease free plants, so you should not have many problems with them.


Harvesting should usually be done at the end of August. Remember: your onions will go dormant at full maturity. The inner leaves will stop producing blades, and the hollow, center neck weakens. This will cause the tops to bend over. You have to allow the plants to go dormant before harvesting. You need to allow the onions to go dormant or else they won’t store well.

When the tops are started to brown, with toppled tops, the bulbs will develop skins. This is when you should tip bulbs over to break the roots. This will speed up drying. However, it’s important not to bend the tops over before the bulbs are mature, because it will only open the risk for a disease.

After the tops have withered, you should pull the bulbs out of the ground and place them in a warm, dry and airy location. When you take them out of the ground they will need some time to cure before they are ready to be stored. Make sure that they should be out of direct sun and with no contact with moist soil. You may spread onions out on a screed and dry them on a warm porch or in a garage or a shed.

It can take up to three weeks to cure your onions before you can store them. Once they have dried up, you should cut the foliage back to about 1-2 inches from the top of the bulb. In case you want to make a decorative onion braid, however, you should keep the tops on.

Store the crops in a cool, dry location. Make sure that the chosen location has a good air circulation. You may store the onions in a traditional onion bag or in a shallow box. Make sure to use newspaper to divide the bulbs. Alternatively, you may place an onion in a pair of old pantyhose and tie a knot above the onion. Make sure to tie knots between each bulb. When you want to use a bulb, simply cut below the knot.

Keep in mind that not all onion varieties are good for long-term storage. For example, the large, sweet varieties such as Ailsa Craig Exhibition or Lancastrian have to be used in a couple of months after harvest. As a general rule, onions with thick necks should be used soon. Those varieties suitable for long-term storage have dry, firm bulbs with tight necks, and layers of protective skin (yellow or brown). These onions are typically sweet and pungent and they become milder the longer they are stored.

Photo credit: Distant Hill Gardens via photopin cc