are light levels impacting germination?

[bluebell]

I have several lots of seeds on the windowsill to get going whilst it is still rather chilli outside and was wondering if the current weather and more specifically light levels are causing very slow germination? Im having particular issues with red onions and parsnip, neither of which are germinating very well. I appreciate that they are not fast to get going at the best of times but Parsnip have been chitting on window sill for 2 weeks with no sign of activity and onions in seed tray for 3 odd weeks again with no sign of activity at a steady 65

[Andrew Pearman]

Hi Bluebell,
I have also experienced very slow germination of red onions. I sowed Red Spark on 11th Feb in modules on warm sand and some seed is still germinating now. If I remember there was nothing showing for 3 weeks or so. I found standard onions(Hytech) sown on the same date germinated much more quickly. Not sure if this is a characteristic of red onions, or to do with the seed. The Red Spark seed was from last year and the Hytech bought fresh this. I think your parsnip seed will germinate in time as long as the seed is fresh.
Andy

[charles]

 Yes it is a slow start to spring, even in a greenhouse because of less sun meaning less warmth. However that does not apply to windowsills of a house.

I think it unlikely that light levels are affecting the germination of seed in compost. More to do with temperatures which are also low. (In fact the mean maximum temperatures in Britain have shown a small decrease in the last 17 years, possibly due to jet contrails – the overall warming trend is because nights have been warmer).

As for onions, my Red Baron are coming up fine, at the same speed as other onions. But the Mammoth are slow and that may be becuase of seed being older. I fear this can often be the case if seeds given the correct temperature are slow to germinate, and then do so erratically rather than all coming up together. Last year my main sowing of Sturon produced hardly any onions, so I had to plant some sets.

Parsnip should be up after three weeks, if still nothing after four then I would resow with new seed.

[bluebell]

Onions are just starting to show through from sowing on 16th Feb! Not a great level of germination but at least some signs of life. They were 2 different varieties and both newly purchaced from different suppliers so the only other thing I can think of is the compost, but other seeds are doing ok in it.

Now my dilema is what to do with them until the weather picks up a bit.

[bluebell]

First sowing of onion seeds was so poor I decided to ditch them and start again. Sam seed, same window sill, only difference is I think the first batch were in John innes No2 and the second in New Horizon organic compost. Second batch has germinated quite well at about 50% as opposed to previously less than 10 %.

Anyone know why this would be?

[charles]

Getting better, but 50% is still too low, it should be at least three quarters and the legal minimum for germination rates is over 80%. 

Last year I had poor results with John Innes no. 1 seed compost and don’t want to use it again.

My best results this year are from my own mix of old garden compost and manure, not too fine: beetroot came up almost 100% compared with 60% in West Riding multipurpose which is a little dense for some seeds. Onions and cucumber also good.
The New Horizon is quite "bitty" and that helps drainage; seeds need air.

[Author]

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