Onion Seeds have Germinated – 5 to 12 days from Sowing

20th Jan 2025

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Thanks for joining me on my first Onion Seed Sow Along on 11 January 2025.

If you haven’t watched it yet, here’s the Video Link: Sow Onion Seeds With Me and there’s still time to Sow Onions from Seed:

When to Sow Onions from Seed

Indoors on a windowsill in January & February &
Outdoors direct in the ground in March.

Day 5 – Onion Seed Germination

As you can see, Onion Seedlings are just about popping their heads above the soil in 5 days.

This cell tray has had the lid on until this point and we have had some cold nights but the room temperature and the humidity in the lid has made it cosy for the seeds to germinate.

Day 12 – Seedling Growth

Here’s what your seedlings will look like after 2 weeks. They look like blades of grass, some might be bent over and some still with the seed heads on. These are all ok.

The ventilation lid should be removed by week two as your seedlings would have reached the top of the lid.

Give them a light bright windowsill to help them continue their growth.

What happens after your Onion Seeds Germinate?

Remove the ventilation lid – when the majority of seedlings are up above the soil or if your seedlings are touching the top of the lid already.

Give them Light! – They now need lots of light to grow so I’ve moved my tray to the middle of the windowsill as it was in the corner. The middle of the window gives it light all around the tray.

Turn the Tray – Turn the cell tray every few days so that your seedlings are not leaning towards the light. By turning your tray, you are getting them to try and grow straight upwards as opposed to leaning towards one side.

Water if the Soil is too Dry – By Week 2, I hadn’t watered my seedlings and they were still thriving on the water I gave them 2 weeks ago. But they definitely needed water.

See my ‘Top Tip Video on how to tell if your seedlings need water’ below. Check every 2 weeks to see if water is required.

Try not to overwater, as mould thrives in wet conditions and could eat away at your seedlings. It’s better to be on the dry side than too wet.

* Top Tip – How to Check if Your Seedlings Need Water – Video *
You will need: A Pencil

Click here if your video is not loading – to view on the website.

How to Check the Water Content of your Compost

Using a Pencil, gently push it into the side or corner of the cell tray away from the onion seedlings.
Pull out the pencil and see if it has any compost stuck to it.
Compost Dust or nothing sticking to pencil = Dry Soil & Compost Stuck to pencil = Wet Soil.
If you have dry soil, water the compost lightly, until you see the water in the tray under the cells.
The cell tray should not need watering for another 2 weeks. Test soil again then.