That's a good question I think. Pons shows similar meanings for voll and voller, albeit voll seems more widely applicable: http://en.pons.eu/translate?q=voller
Interestingly enough, they translate "The glass is full of water" as "Das Glas ist voll Wasser." Which suggests that you could probably say "Der Garten ist voll Leben." here. (I'm not 100% sure about this; but I don't see why not. Maybe Christian can comment on this.)
I sure could use some instructions on when to use voll and when to use voller.
Every time I listen to this, I hear "Lieben", not "Leben". (I got the transcribe activity). I listened to google translate for both words togther several times, and google gives Lieben the long e sound that ie makes. Dict.cc has recordings of real people - of the 4 people who pronounce Leben, 1 pronounces it like Lieben, and the other three make it sound like Ley-ben. Does Duo's audio sound right to native speakers?