Does a seedling require the same temperature as before it germinated?

Evening all,

I wish to prioritise the warmest highest levels in my polytunnel and I was wondering if it would be OK to drop a few levels the seedlings which have emerged and replace them with newly sown seeds?

I say this because I am wondering if the seedlings can handle slightly cooler conditions as I can recall reading a seed packet some time ago which stated different temps (highest required until germination) on it.

Does it relate to specific plants or is there a general consensus for a higher temp required for germination?

Thanks for your help (if you can understand what I am getting at!),

Samuel

Hi Samuel:

I think you'd be ok to swap out the seedlings for a cooler spot as long as it's not a HUGE difference in temps - a few degrees isn't going to hurt them.

I'm not talking proper warm weather plants here, only tomatoes in my temperate climate.
I grow quite a few tomato seedlings for sale, and need to start them early to have them big enough on NZ's traditional planting weekend.
Nights are still pretty cold in early spring here-but we're talking NZ cold, so above freezing.
You shouldn't be too cold in the UK though...
I use a heating pad set around 18 Celsius/65 Fahrenheit to germinate, and as soon as they're up, they go in a cold frame.

In my experience, once a plant's above ground, the most important thing is having it in as much strong, direct light as possible.
Insufficient light and plants are always a bit pathetic, skinny and 'stretched', whereas if they're too cold, growth just slows till they warm.
Tomatoes are special: they grow 'adventitious' roots and it's generally encouraged to transplant them right to their top leaves.
A bit of stretching isn't the end of the world.
So in a really roundabout way, I'm saying if the plants aren't tropicals and there's really good light, I'd say you should be fine

i germinate my plants in an unheated greenhouse. in this greenhouse is a smaller greenhouse type box. inside it is a heat cable. i use this to germinate my plants as higher constant temp gives a better germ rate and speed. once they are germinated they go into the cooler greenhouse where night temps that get low keep them from stretching and becoming lanky plants.

so the answer is yes as long as there getting good sun after germination.

all good advice above
For awhile now I have been paying much more attention to optimum soil temperatures for seed germination...especially the things that I start in my living room.
As soon as they emerge and have their true leaves they are off to the the kitchen where the sun is and much cooler temperatures...we don't have a greenhouse.
I had a chart once that listed a lot of different seeds and the best temperature to germinate them...here is a link to one...here I do remember that many of the temperatures were much warmer than you would expect the plant to do well at...lettuce was 75 degrees F and several things were listed that you would consider cool weather plants but germinated best at warmer temperatures.

good luck!

Jordan Lowery wrote:i germinate my plants in an unheated greenhouse. in this greenhouse is a smaller greenhouse type box. inside it is a heat cable. i use this to germinate my plants as higher constant temp gives a better germ rate and speed. once they are germinated they go into the cooler greenhouse where night temps that get low keep them from stretching and becoming lanky plants.

so the answer is yes as long as there getting good sun after germination.

Hi Jordan, I have a similar situation in zone 6/7. I have an unheated greenhouse and I built a greenhouse shelf within it. In my hoophouse I use very low watt rope light to warm up a shelf for early spring seedlings but in this greenhouse I'm hoping to put some sort of heat cable (as low watt as possible) with a thermostat control to keep the inner box around 70*. The shelf is 10' long by about 2' wide. Can you recommend a type of heating cable/controller or anything I should be thinking about when I shop for them?

Many thanks!

It depends on what species it is.

I've sprouted many stonefruit seeds in the fridge. I have to wait until there's a taproot about an inch long, to where the seed itself is not touching the ground at all, before I take them out of the fridge and put them under the grow lights. If I plant them with the seed touching soil at room temperature, they will usually succumb to mold.