Richard Hawke is plant evaluation manager at the Chicago Botanic Garden, where he conducts long-term trials on dozens of ornamental plants. For the past 22 years, he has evaluated more than 200 clematis varieties, then tabulated the results of those available today for purchase by gardeners.

You’ll find Richard’s top picks and why he likes them in “Big Blooming Clematis” in the July/August 2012 issue of Fine Gardening (#146). We couldn’t print the full results of his study in the magazine, but we can offer many of them here as a download.

The chart includes more than 100 clematis varieties. In addition to Richard’s rating (on a scale from one to four), each variety is characterized by flower color, size, and coverage; bloom period; plant height; and group (an important designation for pruning). If you’re in the market for a new clematis or if you want to get an expert opinion on a plant you already have, download the chart and take a look.