The "Early Sunrise" variety of Coreopsis grows 1½'-2' tall in my garden.  It is supposed to bloom from June to frost, but I wouldn't know because they keep dying on me.  It seems that the roots never develop fully.  The only thing I can think of is that the soil where they were growing was too heavy.  In 2003, I moved the only one I had left to another garden bed that has a lighter soil.  I also grew another four from seed.  They grew really good in their new location, but three of them died over the winter of 2003-2004.  To add insult to injury, the groundhogs ate most of what was left of them.  We'll have to wait to see what comes up this year.  It's supposed to be a good butterfly plant, but I couldn't tell you.