The Hardiest of Hardy Perennials. Generally speaking, a plant is classified as a perennial if it can survive to Zone 7. Above that range, plants become tender perennials or annuals. For the purpose of this article, we will only consider the "hardiest" of hardy perennials, plants that are hardy to Zones 4 and lower (or higher in latitude). The plants on this list are definitely tough enough to survive your area's worst winters.
Festuca Boulder Blue - Discovered in Colorado, Boulder Blue has a much brighter steel-blue foliage color than the more commonly available Elijah Blue. This hardy, perennial grass forms tufts of metallic-blue fine foliage from early spring through late fall & even into winter. Festuca Boulder Blue takes intense heat & drought without losing its blue color and makes the perfect addition to patio/deck container gardens. Special Features: Cold Hardy, Disease Resistant, Easy Care, Fast Growing
Artemisia- Artemisia has beautiful silver-gray foliage that won’t fade in the hot sun. This hardy perennial is also drought and insect resistant, and the branches make a wonderful addition to indoor flower arrangements.
Sedum Drought-resistant and almost foolproof, sedums return year after year with no complaints. There are many species of sedum to choose from, but some of the toughest are the groundcover varieties, such as 'Dragon's Blood', shown here. These easy-care creepers will slowly carpet your garden with color even under extreme weather conditions. Zones: 3-7