Garden failures

For a couple of beginners, we've been fortunate that our plants have done so well, but we'd be less than honest not to tell you about some of our failures:

Smoky Hills. This pretty purple-bloomed plant (along the base of Rock Hill Garden) captured our hearts when we saw it at the arboretum plant sale. Ken grew up in the Smoky Hills of Kansas, so of course we had to have some! But something about this spot didn't agree with our Smoky Hills (too much afternoon sun?) and it died. Fortunately, we were able to transplant one plant to the flowerbed at the entryway, and it is thriving.
Moonlight Broom. For reasons unknown, this beautiful, unique plant only lasted three years in our garden before giving up the ghost this spring. We held out hope, until early June when we finally dug out the shriveled root. Blue Dune Lyme Grass. Its blue hue contrasted beautifully with the lawn. The first year it was mild mannered, but after that, it tried to take over our world (the label warned us, but we turned a blind eye.) Finally this year we got aggressive and fought back with Roundup. It would be a great plant to fill in a large, contained area, but not here, where we prefer to see Catmint and Rose of Sharon thrive.
We've had some other wildflowers that bloomed beautifully one year and didn't come back (Cornflower, Coneflower and Coreopsis...hmmm...all the "C" plants?) and others that we planted that never showed up (New England Aster, Lupine and Stiff Goldenrod). But Cupflower, Butterfly Milkweed, Wooly Verbena, Yarrow, Columbine, Spiked Gayfeather (Liatris) and a host of others return faithfully each year.