When to plant onion sets – gardening season is now on!

Onions placed on a white table

Onions are used in many dishes by everyone all year long. If you think that planting onions is secondary in thought you are wrong because there is a lot to be considered in order to have a bumper crop of this centuries old mainstay.

Planting onions

Onions are easy to grow and are planted in the spring season but they are harvested in the fall. It is doesn’t matter if you start growing onions from seed, seedling or sets, there are always going to be some tricks which can make the differance from a great crop and a bad one. This article will help you in finding out how to plant onions.

How to plant onions from onion seeds

Planting onions from seed may sometimes be even necessary in colder climates. Onions from seed will grow in soil which is going to be at least 50°F to germinate. Thats why they should be started inside for about 6 weeks before transplanting it to the garden.

If you want to reach early summer harvest you should plant them in spring. Think about starting your onion seeds 12 up to 16 weeks before last frost date.

Planting onion sets

Many people prefer planting onions from onion seeds than starting onions from seed. Why? Because sets establish way quicker.

Onion sets are simply just very tiny onions which gets mature in about 14 weeks. You should plant them in the garden 2 to 4 weeks before the lat frost date which was in your area. You should dig deep enough hole to burry them (the bulb is supposed to be mostly under the soil however its pointed tip level should be with the soil surface). Onion sets are supposed to be spaced about 4 up to 6 inches apart. So remember to space onion sets for its good.

Type of onions

There are few onion types. Those types are:

  • green onions – those onions are also known as scallions. If they will be allowed to grow for a bit longer and form bulbs they are considered as spring onions,
  • bulbing onions – those onions are simply tradicional onions,
  • spring onions – this kind of onions are simply just young onions which are harvested before the bulb shows up.

Onion varieties

There are onion varieties like:

  • short day onions – this onion varieties forms bulbs durning daylight hours increased 10 to 12 number of daylight hours. Short day onions which are grown in the north may flower too early in its season when days goes longer. Those vareties are for example Grano, Red Burguandy or Vidalia,
  • long day onions – those onions will provide with bulbs when they are provided with at least 14 hours of daylight hours or even more. Long day onion varieties are for example Walla Walla, Rosa di Milano or a Red Carpet,
  • day neutral onions – those varieties are also called intermediate day onions. They form bulbs with 12 to 14 hours of a daylight. Those varieties are for example Talon, Sierra Blanca, Gladstone, Cabernet.

When to harvest onions?

Onions in a pot ready to harvest

If you want to use as green onions you should harvest them at any time after they are in the size of a pencil or starts to form bulbs (good tip is to trim the tops occasionally to enjoy the green onions and leave the bulb to continue to grow).

When onion bulb form you can harvest them just when you will want to use one. It is the best feeling ever to harvest a fresh onion for dinner when it is needed. To use their maximum storage potential as dry bulbs you suppose to let them grow and reach full maturnity.

Onions are ready to harvest when the main stalk gets weak, thin and when flops over.

Tip: be gentle while harvesting onions. Onions are very susceptible to bruising.

Pests and diseases

There are couple of pests and diseases which can touch onions:

  • thrips – if you want to control thrips take a dark piece of paper to the garden and knock the onion tops against,
  • white rot – this is in fact very serious disease which starts with infection of a plant material. Transplants grown in soil based compost should be avoided,
  • onion maggots – to help it you should cover emerging onion crop with a fine mesh netting or row covers. Also a good idea would be to keep mulch away.

How to store onions?

  • to cure onions just leave them on a dry ground (for example in a garage),
  • when onions are cured you can hang onions for example in a mesh bag,
  • check them time to time if there aren’t onions which are rotting or sprouting,
  • do not store onions with apples or pears.


  • it is okay to grow onions almost any time of the year, there is no concern needed for day length,
  • in early spring or fall mix aged manure or compost into the soil this will improve its texture,
  • if you will want to pull immature onions try to do it as they are scallions,
  • many gardeneres likes to add about an inch of compost tea before they will plant onions,
  • plant onion seeds in spring indoors about 6 weeks befor you will transplant them to the ground,
  • you should water onions as soon as you will plant them outdoors – remember to water them regularly,
  • there are red onions, white onions and of course yellow onions,
  • well drained soil is very important durning transplant to the ground!
  • if you want to plant onions in tropical climate the best way for planting onions is to do it with help of raised beds,
  • onions grow best in a soil ph between 6.0 to 6.8,
  • if you want to plant onion seeds you should plan to plant them somewhere around 8 to 10 weeks before the average last frost date,
  • mulch helps to retain moisture and also stifle weeds
  • if you want to go for spring plantings you should be planting onion sets in the ground no later than a month before last frost date,
  • if is quite helpful to think of an onion as a leaf crop but not as a root crop,
  • if you want to grow onions from seed you can do it in both ways. This means that you can start seeds indoors as well as sow seeds outside,
  • it is a good idea to water onions at least once with a compost tea durning the growing season,
  • it is fostering healthy foliage growth that ensure plant to have enough energy to the large bulbs,


We hope that this article taught you couple of things which will enable you to grow flavorful onions. With its help you know how to grow onions and how to store onions as well.

You can have fresh onions or just simple small green onions from your own garden isn’t that great? All you gotta do is plant onion and you can have diced onions which will be your own in a salad!

Now you know the best ways to plant onion bulbs and sets so go on and start onion planting!