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.
Make your flower border more interesting by pairing perennials with different flower shapes. Here, for example, the skinny, bright blue flower spikes of veronica contrast nicely with the fat, rounded blooms of coneflower. Planted individually they are lovely, but grown together they put on an eye-popping show.
Fragrant Perennial Plants Phlox 'Creeping' - Thrift A carpet forming Phlox that is covered with sky-blue flowers in Spring. Excellent for use as a border in the landscape or perennial garden, or on slopes. Very drought tolerant.
Keep foliage color in mind when you plan your perennial border. Plants with colorful foliage such as artemisia will keep the garden looking good while flowering plants go in and out of bloom. 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. Height varies by variety and can range from 3 feet tall to just 5 inches. Grows in Zones 4-9.