On Apr 27, 8:43*pm, "Jane_Galt" wrote:
What are good perennial bulbs for Colorado ( zone 4? ) , that can be planted
in spring, will bloom in summer, and spread each year?

Dahlias should fit the bill. One caveat is that you have to dig them
up for winter, or buy new tubers each spring. If you divide them after
digging up, you get an exponential growth in the number of plants each
year though.

Strong points of dahlias are that they bloom for months and months,
and offer great variety - there's thousands and thousands of very
different cultivars available. Just search for dahlias on http://images.google.com/
to get an impression. Also, AFAIK there is a rather active dahlia
society in Colorado, which can be a big benefit (or, at least you know
somebody grows the flowers in your state... ).