sowing onion seeds - when?

[aquilegia]

When should I sow my onion seeds?

Some say January, others say Late Feb/March.

I now have a heated propagator, if that helps.

(Oh heck - just realised I need more room in my roots and alliums bed. I've only got room for onions or leeks, but not both. More digging...)

[aquilegia]

[philcooper]

For big ones, go for it now.

My Kelsae have just germinated they took 7 days at ~18 degrees C

The advice from growers of exhibition size tubers is to sow them 1" apart and prick out into individual pots AFTER the curl has disappeared

Phil

[aquilegia]

If I don't want big ones, but plant them now, can I harvest them earlier?

I was going to sow them in clusters, so save space (very limited in my little patch!)

[philcooper]

I believe, and John will no doubt say if I'm wrong, that onions stop bulking up around mid summer so the longer they are growing the better.

Hence sowing now will give them a good long growing season and allow them to reach their maximum under whatever conditions you choose ie they'll be bigger if sown now using your clusters than if you do the same later

Phil

[aquilegia]

Thanks Phil

I think I'll give it a go at the weekend. I'm itching to get some seeds in the compost!

[Moggle]

Hurrah, I'm going to get mine going too on the weekend  :)

[Mothy]

I sowed some last weekend (Ailsa Craig I think) but in a cool greenhouse so I guess maybe a little slower to germinate?

[john_miller]

Aqui, just to clarify Phil's comment. Your onions will start to bulb when daylength decreases beyond a certain point. The bigger the plant is at this point then the bigger will be the bulb but you will not get them any earlier (all other things being equal)- at least I have never seen an onion cultivar sold as 'early', but mostly only on their ability to store well. Adequate potassium in the soil is also critical to increase bulb size and to improve storage life.

[aquilegia]

Thanks John. Potassium - should I give them tomato feed then? (Or have I got completely mixed up?)

If I sow them this weekend indoors, when can I start hardening them off and get them in the ground? (I'm trying to be ultra organised and plan where and when everything will be in the ground!)

[growmore]

Mine were sown on  boxing day .In  another Fortnight or so they will be ready for pricking out into pots.They need growing on then at around  50-55 degrees .They can be put into cold frame around March time dependant on weather.
Then planted out to their final growing position late  April to
early May .
Like Phil Cooper mine are Kelsae and also Alsae...So I am hazarding a guess Phil is going for big ones like my self..
For onions for the table as in Ailsa Craig etc I would delay sowing till Late March. Jim..

[philcooper]

TimJ

Here's a reply I prepared earlier

According to tables in Mel Bartholomew’s Square Foot Gardening, onion germination rates and times are, against temps in degrees C:

0   136 days    90%
5    31 days    98%
10   13 days    98%
15    7 days    98%
20    5 days    99%
25    4 days    97%


Phil

[aquilegia]

Phil - that is interesting. They germinate quickest at 25, but more germinate at 20. So hottest isn't necessarily best. Is that the temperate at the top of the soil?

I put my propagator on with nothing in it but a thermometer, just to test how hot it got. It went up to 27 deg!

[john_miller]

No Aqui you haven't got it wrong. Like any plant give them a balanced fertiliser initially with a shot of K, probably around summer solstice, to help development of bulb tissue. Tomorite is an excellent source as its liquid formulation will be readily available to the plant- I wonder if the manufacturers should change the name as they may be losing sales with a name so closely identified with one vegetable?
I'm no statistician but I wouldn't pay too much attention to the differing germination percentages at various temperatures in this instance as I don't think they would be considered outside of margin of errors and would be down more to plain luck. Having said that, excess temperatures (30C or more, although some are inhibited at lower temperatures) will cause germination rates to decline with many seeds.

[campanula]

my god, don't they look like feeble little things )i grew sets last year) Bedfordshire Champions from seed, 1st January this year.

[philcooper]

Aqui,

I agree with John, there is also the adage to grow 'em tough.

Too high a temp will produce plants which very quickly "outgrow themsleves".

So the optimum for a good crop would be to germinate at as low a temp as you are prepared to wait for the germination and you don't loose too many - French Beans for instance don't germinate at all (they just rot off) below about 15 degrees

Phil