Dahlias

I bought a couple of dahlia roots on a whim and put them in a container in the greenhouse over winter.  They seems to be growing in there now. Is it OK to plant them outside or wait a little longer?

Thanks for that advice. I'll have to nip down today and water them.

we usually dig our dahlia up and take them from the allotment back home to the greenhouse but this year we did something different we left them in the ground and covered them over with a thick base of straw to overwinter
 
we did go down the allotments the other week but didn't see any sign of dahlias shooting through the straw when the weather warms up we hopefully be able to go to the allotments and take the straw of to give them a chance to grow fingers crossed