A Great Plant for New Gardeners
If I had to give just one easy care plant recommendation for new gardeners, it would be Yarrow (ie, Achillea). Yarrow is great in any soil, does not require much water and multiplies very rapidly. It thrives in the heat of the Summer, rarely ever wilting! The average height is 2', and it is available in various colors (except blue).
This group of Rose Yarrow was planted last Fall and has multiplied from two small plants purchased from Lowes.
It hasn't started blooming very heavily yet, but when it does, there will be masses of these lovely pink flowers on the tops of all the stems.
Bluestone Perennials has a nice Yarrow offering showcasing the different shapes and sizes of Yarrow available on the market.