I’ve tried other tall ageratums over the years, but I always go back to ‘Blue Horizon’. This mid-to-back-row annual grows 24 to 30 inches tall with fluffy blue-violet flowers that mix well with just about any color in the garden.
For the last couple of years any tall ageratum I grew wouldn’t reach its expected height which was a little baffling, so I started planting them in the 2nd or 3rd rows of my flowerbeds instead of the 4th. ‘Blue Horizon’ was still the tallest and the most reliable, and this year my plants are back close to the higher end of their expected height (30″).
I like growing ageratums because they have no disease or bug problems, and they bloom all summer long into fall if you keep them deadheaded.
‘Blue Horizon’ seeds were getting harder and harder to find, but this past winter a couple of seed companies started selling them again. Until someone can come up with a better cultivar that has lasting power, I’ll keep growing this “oldie but a goodie.”