Zap-A-Gap 

Click Here

Now being offered in a larger, 1/2-ounce size. 
This is a 'super-glue' type adhesive that actually pulls itself into tiny spaces to fill gaps (hence the name). I use it with Instant Grrrip to make my flower parts and leaves stay in place immediately during assembly of plants and shrubs. Simply apply Instant Grrrip, then a teeny, bitty bit of Zap-A-Gap and your plant parts will attach to stems instantly!