Skip to Content

Onion Seeds V Slips V Sets (What’s The Difference?)

Sharing is caring!

When it comes to growing onions, there are three different ways to start your crop. These are Seeds, Sets & Slips, but what are the differences between these three methods?

Let’s have a look!


Seeds are the cheapest way of starting onions, but not the easiest.

Growing onions from seeds is a long process, and ideally, you need an indoor area to start them off in early spring before moving them outside later.

I do grow onions from seed and use the multi-sow method.

This means I sow the seeds into module trays but sow three or four seeds per module rather than growing them individually.

The onions then grow as a cluster when you move them outside. You don’t thin them out; transplant the entire module.

Pros & Cons


  • The cheapest way to grow onions
  • Lots of choices when it comes to variety


  • Slow to grow


Sets are the most popular way of growing onions, in the UK at least.

A set is essentially a small bulb that has been partially grown before being made dormant again.

You then plant the set, which grows into a full-sized onion bulb.

Pros & Cons


  • Easy to grow
  • Can be direct planted


  • More expensive than seeds
  • Can be more prone to bolting
  • Less choice of variety than starting from seed


Slips are not something you see all that often in the UK. They are more of an American thing.

They do pop up in advice articles from time to time, so I thought I would explain what they are to prevent any confusion.

Onion slips are essentially mature seedlings that you transplant.

They are bought from garden centres like this in the USA, but it is not something we really do. Think of them as somewhere in between a seed and a set.

Pros & Cons


  • Easier & Quicker to grow than sets


  • More expensive than seeds
  • Less choice of variety than seeds

How to sow onion seeds

I sow my seeds in early spring indoors under lights. Because they have such a long time to maturity, planting the seeds early is essential.

I multi-sow them in a seed tray. This means I sow and grow a few seeds per module rather than just a single seed.

Once the soil has begun to warm in mid-spring, I transplant the clusters outside, keeping them as one clump rather than separating them.

Sharing is caring!