|I have a plan that calls for Ageratum houstonianum in the bed. This is an annual, I believe. What do you recommend
as a perennial substitute. Most of the bed is blues/purples, yellow and pink.
|You might like Eupatorium coelestinum instead, it is sometimes also called perennial ageratum. The color is very similar but the plants are taller, about 18 inches, and they bloom in the fall. If you need lower growing plants, you might like Ceratostigma plumbaginoides which blooms blue in late summer and then its foliage turns a dramatic burgundy in the fall. Both of the above can be spreaders in overly rich soils. Alternatively, the asters would provide a range of colors in the purples, pinks and blues for you.|