1 Salvia nemorosa 'Caradonna’ from the mildly aromatic silvery green leaves to the violet flower spikes with purple stems. Bees love the flowers that stay looking sharp long after the petals fall, thanks to papery bracts that hold their colour. Dead-heading – either little and often or in one go – encourages new flowering side-shoots till October. 'Caradonna’ loves sun; use it as a purple ribbon through late season grasses or, at 18in (45cm), it is the perfect centrepiece for a pot.
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.
Camassia leichtlinii Alba Camassia leichtlinii Alba is a statuesque late-spring flowering bulb with spires of creamy-white flowers which last for ages. One of the most tolerant and long-lived bulbs you can grow. They're ideal for being happy in sun or light shade, for naturalising.