Glowstone Tree layout

[penna]

Hey people, had a little search before hand and couldn't find any details...

Does anyone know the best layout for glowstone trees? I'm having issues with some not growing (i'm guessing due to spacing) and wondered if people had any specifics on spacing between saplings, height restrictions? (could a roof be added or would that affect growth?)

Thanks in advance for any advice. Im a rather efficient builder so like to maximize yields wherever possible

 

[Xavi | Goofy]

The problem is probably the surrounding. A tree needs around 2-3 blocks horizontal space outwards and 4 blocks of ceiling.

 

[penna]

I thought it may of been ceiling, thanks

May need to do some testing to find out max possible growth dimensions so I can build accordingly. Im a little ott with these kinda things lol