[Bodmass]

As the temp drops back down to seasonal norms I'm faced with a choice between maximising light to my tomato (& chilli) seedlings, or keeping them warm.

I live in a flat with an south-east facing balcony & small windows.  I have a plastic growhouse sitting on the balcony which has been adequate for most flower seedlings & due to the higher temps I have had my tomato seedlings there.  This gets direct sunlight till (maybe) 10 or 11am but is at least getting some light for much of the day.

My windows are even more limited in the light they get (2hrs less direct sunlight & darker for rest of day) but is obviously warmer than the growhouse.

Hence my basic question, which is more important at this stage, heat or warmth?

[8doubles]

Light during the day and heat at night !

Seeing as you haven`t asked if you started them too early i will not say anything else.

[TheSpartacat]

I honestly think that even with the warmer days we've had recently, its way too cold at night to house tomato and chilli seedlings outdoors, they won't thank you for it. They sulk if it drops below 10C (and even then, i think they prefer it warmer)

I get similar lack of light... but i manage with the chilli seedlings by putting reflective tin foil behind them. I've also replaced my bulbs with daylight bulbs (more blue spectrum) which are about £3 or £4 on ebay... You can use these in one of those bendy lamps pointed at your seedlings and it will help a little.
Chilli's need an early start... tomatoes on the other hand can be sown outside in your growframe at the end of March/early April and will catch up on any that have been started indoors... so i would recommend doing a second sowing around then as a precaution.

[Yorkie]

Tomatoes will sulk and go blue (literally) if they get too cold, and often do not recover from that.  The general advice is that anything under 10 degrees at night will check them as described.

I won't be starting mine off for another 4-6 weeks as I only have windowsills and one of those 4-tier mini greenhouses.  There's no point in risking them outside before the end of May, and they will be far too leggy if started off too soon.

[DD.]

My outside and unheated greenhouse ones will not be sown for another 2 weeks, but I've got a heated greenhouse to keep them in in the interim.

Yorkie's right about not sowing for another 4 weeks or so without those facilities.

[Bodmass]

I planted 5 with the intention of planting another 5 at the end of the March as a comparison (only need 3 adult plants).  Maybe I'll just throw the first batch away then, plenty more seeds in storage!

My hours/the fact I stay at home rarely does unfortunately mean that I often wouldn't be able to return them to the growhouse until after they've missed out on the direct sunlight 

Had been thinking of blasting a hairdryer in the growhouse for 20 mins at 2am to try & keep the edge off (a trick I'd used before with standard flower seedlings).

So to the specific query, basically we're saying that BOTH heat & light are equally important.  Cheers.

[TheSpartacat]

So to the specific query, basically we're saying that BOTH heat & light are equally important.  Cheers.

Yup!! Lack of heat can kill them... lack of light will stunt their growth and make them leggy.

[Totty]

Many of the new F1 hybrid tomatoes come with a sowing recommendation of febuary. Heat and light are both important. My tomato plants are now around 5 inches in height. They are not drawn or leggy at all and so long as the temp in the growhouse inside the greenhouse stays around 10 degrees at least, rising significantly during the day, they will crop earlier, and will grow more trusses of ripe fruit meaning no glut of green ones in autumn.
I would say you must keep them warm to keep them alive, give them whatever light you can.

Totty

[Yorkie]

One does need to distinguish between the sowing dates for those people with heated greenhouses, and those people without them.

If I followed instructions to sow in February, on a windowsill indoors, I would have tall, weak leggy plants by the end of March owing to insufficient light levels (despite foil) and would have to keep them indoors for another 2 months before it was safe to plant outdoors - this date not being negotiable.