You're not going to be able to leave the plant in there, unless it's a clone. A seedling needs fresh air. It's better if you take the jar off.
Perp Reviewed by Perp on . Chetto Sprout/Incubation Dome This was made using a plastic 4lb Jelly Belly® jar, a salvage light socket, and a 23W 2700K CFL. I used a steak knife to cut out the whole bottom, and put in 3 x 1/2" vent holes, and a circular hole in the lid big enough for the bulb base, but not the socket; the lid is a "washer". Currently in use an hour, and temp is 78°f at pineapple level. If I see high temps. I'll cut 3 x 1/2" vent holes in the bottom section, to allow convection. Rating: 5