I agree with BlackFatalii,
No need after germinating. HOWEVER, depending on what climate you are in, and what the temperature is of where you are starting you seeds, leaving the heat mat on MAY help speed up the growth rate on young seedlings.
Plants love warm ground... not hot... warm. This is how Mother Nature brings seeds to life in the wild.. with a warm ground, rain and sunshine. All we are trying to do is replicate what God does outside...inside.
As for me, I start 600 seeds per year... that is way to many warming mats so I use a grow tent and a 1000w hps lamp... the lamp produces heat and that, keeps the seeds warm. Some say don't use such a high power lamp for seedlings.... but, the sun outside doesn't dim for new seedlings... Why should the lamp...
Using a covered seed flat.with a heated map. Not grow lights turns on yet... currently in a south facing window in san fernando valet.
If half the seeds germinate, should i move that half out while waiting for the rest? Or maintain until all germinate? The ones i considered to move do not have true leaves yet.
many thanks. yearly container gardener but first time with seed start !
Light is an interesting topic. I am out of room in the grow room. So have started germinating in a closet because it is small enough to heat. My thought was as soon as they pop, move them under lights. Thing is, germination is absolutely horrible compared to seeds germinating under lights. All I can figure is the gentle heat on the top might send a signal to the seed. Just speculation, seems nutty.
AJ, have you checked the soil temperature with and without lights? Currently my seedling tray is running about 73 F with the lights off, and around 83 F with them on. They are just CFL lights placed about 4-5 " above the soil. I am thinking that maybe it is the additional heat, rather than the lights themselves that are making the difference for you. I have had very good germination rates with your seeds without using any lights, as long as I kept the soil temperature around 80F.