Which is more important to seedlings, heat or light?

[MarkPelican]

Most of my tomato seedlings have now germinated, and I'm starting the annual process of taking them out to the unheated greenhouse in the morning and bringing them back in the evening. It made me think, is this necessary?

If I didn't take them in and out where should I leave them?

On the one hand, growing them on the windowsill will keep them warm (above 10C) but reduce the amount of light. So they'll grow more spindly.

On the other, if I leave them in the greenhouse, they'll get cold at night and suffer that way.

At the moment its only three trays of seedlings but when they are potted up in a week or so, it'll become many more.

Other than heating the greenhouse or having growlights in the back bedroom, anybody any thoughts as to which is more important?

[the big lebowski]

heat is more important to get the seeds to germinate but after that i couldnt say one or the other as both can effect the plants if they get to little of either ,i can understand your problem with not wanting to keep taking them in and out of the greenhouse but i would keep a v close eye on the weather forcasts for any temp drops also a thermometer in the greenhouse would help you alot too as the weather people dont always get it right ,cheers

[Thelma Sanders]

I opt for keeping them warm at night - so carry on with the in/out routine until nights are warmer.
In the past I've tried leaving them out in the greenhouse and they went blue and didn't recover. I've tried leaving them indoors and they get tall and spindly - but at least you can plant them deeply when temperatures pick up a bit.

If you want to keep them in the warm next year, I'd advise sowing a bit later.

[Deano's "Diggin It"]

I'd be inclined to say heat also, as a drop in temp can put a plant in check by weeks, I'm no expert, but never having had grow lights until last year, found keeping em warm although a little leggy, and the crap spring we had, they soon bulked out once put in their final positions!

[Deano's "Diggin It"]

I opt for keeping them warm at night - so carry on with the in/out routine until nights are warmer.
In the past I've tried leaving them out in the greenhouse and they went blue and didn't recover. I've tried leaving them indoors and they get tall and spindly - but at least you can plant them deeply when temperatures pick up a bit.

If you want to keep them in the warm next year, I'd advise sowing a bit later.

And for the said same reason, I'm definitely not in a rush to sow mine anytime soon!

You live n learn!

[fishpond]

Light and Heat are both very important after germination for any plant.
Buy/Make a heat bench/propagator for your greenhouse for next year and you will not have the problem.
Remembering you will need a power supply.
Or you could sow them in late March/April next year, in the greenhouse.

This year you need to continue doing what you are doing if you want the best out of them.

Just think of the taste of the toms in the Summer, especially with some home grown Basil, in a home grown salad. the Toms may not get to the kitchen though.

[Twynyrodyn]

I started some red cherry tomatoes in a heated propagator. When the seedlings grew I potted them, choose the best six and brought them into the house . Because I am a newbie I couldn't kill the others off, so I left them in the unheated greenhouse. A week later I decided that some of the seedlings in the greenhouse looked as good or better than the ones in the house, so I brought another twelve into the house. The ones permanently abandoned in the greenhouse became weak and I killed them off .... eventually. The six that first came into the house look strong and healthy but a bit spindly. The second twelve are sturdy little chaps. All eighteen now make the daily round trip from the house to the greenhouse along with the cucumbers and aubergines. With this and moving my broad beans from the greenhouse to the garden every day I am amazed that I ever get to work on time! Anyway, it seems that the seedlings which were left to get a bit chilly in the greenhouse for a week, but had a bit of an early sunbath are the strongest and sturdiest.

[Bren In Pots]

I'll be sowing my toms at the end of March in a heated prop once they're germinated they stay on a South facing window sill behind a foil sheet that reflects the light.
Then eventually they'll go in the GH during the day until its get warmer overnight. This is what works for me I used to sow earlier but I ended up carrying huge plants between the GH and kitchen..

[jackarmy]

I quite like the routine of carrying them back and forth from greenhouse to kitchen , maybe im weird i dunno .
Anyway, i planted some toms in the gh this season for the first time, think it was the 3rd of march and i tell you what they look cracking compared to my sill grown ones.

I dont worry too much about toms getting leggy as i always plant deep anyway, but the difference between the greenhouse grown and windowsill grown is immense ( ill try and get pics tomorrow lol but no guarentee ).
The gh ones are a lot shorter but thicker and so far, despite a few evenings below 10 degrees their all looking pretty good. I fleece them of course but tbh , yes, their a plant from sunnier climes but the seed we use have probably been brought up in ths country for generations so to speak.
Im gonna try and keep them out in the cold gh with fleece this year, if i fail, then so be it but you know what ?

I think uk bred toms are harder than we think

But oi tink loit and a wee bita warmth to keep em cozy to be sure.

[Jay-ell]

I haven't sown mine yet, wil get around to it in a week or so. If I had sown earlier I would have ended up with leggy plants too long to bury deep in the pots - going in and out the green house isn't an option and with the "sunniest" windows being shaded by surrounding houses theres not much light on the windowsill.

I have a couple of cheap grow lights which worked to bring them on a bit last year before going down the plot later on - so I'll be doing that again this year.

[Alison]

I've not sown mine yet

[MarkPelican]

Thanks for the responses. Looks like I need to keep the transport in and out as always, I was just trying to be lazier.

[coreopsis]

I usually start mine at the end of March/beginning of April. I leave the trays in boiler cupboard which is warm but has no light and start checking after 2-3 days.As soon as they emerge they are going on the windowsill. And this is where the fun starts.
Last year I had to bin my toms because they were too leggy on the windowsill so this year I'm trying different tactic. I'm going to watch the forecast like a hawk and bring the home for the night when frost is on the forecast but if it's "only" cold then will cover them with cardboard box overnight and throw a fleece around.
Tomatoes are much harder then cucurbits and beans and can tolerate much lower temperatures.

Once they get going and have a couple of true leaves they will keep growing albeit on the slower rate if the temperature is low.

[Elfeda]

around mid march I found 3 tomato seedlings in my grewenhouse . they are in pots sown with broadbeans. They were really good and healthy. This made me to leave all my main tomato pots in greenhouse. just incase I kept some outdoor plants like alicanate, and early tomato plants, few chilli and aubergine in one window ledger.

[Baldy]

Deep in the South West it looks like I'm getting away with toms in the unheated GH. They've been out there for a month give or take - and in that time night time temps have not often gone below 9 degrees IIRC
Mrs Balders has a limited tolerance for seedlings on windowsills... so they have to be move on sooner than I'd like.
A chum at the allotment picked up a parafin heater off eeebay for £16 which seems to be keeping his GH at about 15 degrees overnight. I might need to look into an electric heater that I can set with a timer as I can't see Mrs B out at night fiddling with a wick when I'm working away. Anyone have any advice / expoerience with a leccy one (ideally I'd like it to be solar or heatsink powered but that aint gonna happen at least until the boffins make some massive inroads into battery efficiency.