Ooh, this is a new field not fully researched and detailed yet. What type of LED lamp have you bought (wattage, light output, colour, is it a growlight LED or ordinary household one), and what plants are you intending to grow? This thread here might be of interest, but read all the way down - there's some argument about whether ordinary white LEDs grow plants well or not

http://gardening.stackexchange.com/questions/5977/are-household-led-bulbs-suitable-as-supplemental-light-for-plants

As to whether you need the cover on or not, depends on what plants you're growing - LEDs don't really emit heat, so if your seedlings/plants need high humidity and warmth, leaving the lid off might not work.

Colour emission makes a difference, that is, whether the colour emitted contains red, violet, white and so on, and it impacts differently on different plants. There are some professional growers (tomatoes) who exclusively use LED lighting all the time, but they have a mix of white, green and red LEDs, in ratio, for large crops, so not much use for someone at home. If no one else has more definitive information, I think you're probably going to have to experiment...

Thanks flag

flag?

Hi, I think Bamboo has given you, what is probably the best answer you're going to get, I certainly haven't researched this area.
The flag that you see at the bottom of the comment, is to enable you to 'flag' the comment to the administrators if you think there is something offensive about the comment, not the name of the member who has commented, which is Bamboo in the first instance, the members name appears just below their avatar, Derek.

Thanks Derek& thanks bamboo

I'd be interested to know what you grow and how well (or not) the type of light you've bought does the job...