Immediately upon germination. One advantage of using small containers for germination rather than a big kit/tray and why only one variety should be planted in each tray.

If you wait for all or even most of the seeds in a flat to germinate, or mix seeds with different germination times, the early ones are already leggy and weak by the time the rest come along.

If one variety is planted in the container then once germination begins the rest will follow shortly or likely wouldn't have germinated anyway.

Dave

Thanks Dave! I thought I remembered you saying in an earlier post to move them under lights as soon as germination begins, but I began second guessing myself after moving 5-6 flats of onions, because a number of seeds hadn't germinated.... Seems that they're continuing to germinate even after being placed under the lights ??.......

If you think about what would happen if you sowed outdoors, the sun would not suddenly switch on when the seedlings sprouted, would it? So yes, they will germinate under lights. I've never used lights but I would assume the idea of switching them on only after germination is just a matter of economising on the electricity. Am I right digdirt?

just a matter of economising on the electricity. Am I right digdirt?

Basically yes, that and convenience based on set-up used. Usually all germination is done is some sort of confined area/container, enclosed so that soil temps can be maintained. An insulated 'hot box' propagator full of germination trays is common in commercial greenhouses - kind of like a big insulated cold frame full of heat cables.

It's heated to germination temps so that the entire enclosure (GH, basement, room, whatever) doesn't have to be heated. But it has no space for lights of any kind and the natural light even in the GH at this time of year isn't sufficient. So once germination begins the trays are moved to the lighted areas where the cooler temps benefit slow growth.

The exception of course is those few flowers and things that require both heat AND light for germination. They get a special set-up.

So depending on the set-up used for propagation, if it is convenient to have lights there as well, great. If not then the containers need to be moved to the light ASAP.

Dave

Thanks for that, digdirt. I have a small heated propagator which I use in my glass porch/greenhouse. Light setups in domestic situations are very unusual here.