bm writes
I bought two Hyacinth each in a glass container. The instructions were to
keep them in a dark and cool place for about 10-12 weeks
Is it essential to have them in the dark ? I was proposing to keep them in
the garage which is fairly dark and cool

The theory is that if they're in the light, they'll grow top growth
before growing the roots to sustain the growth.

Normally, they'd be largely underground, and therefore dark - in a pot
they're planted high up, so you mimic the dark of the soil by keeping
them in the dark
--
Kay