UNITED STATES—Annuals live for only one year. Biennials live for only two. Technically, all other plants are perennials. Horticulturally, this classification is much more specific. Generally, it does not include vegetation that qualifies as something else. Also generally, plants that qualify as perennial are herbaceous rather than woody. Of course, this is not as simple as it seems.
Palm trees that develop substantial trunks, for example, classify as herbaceous trees. So do arboriform yuccas, such as Joshua tree. Palms and yuccas that do not develop trunks can classify merely as perennials though. Different species of one genus could therefore classify very differently. Tree ferns may also qualify as herbaceous trees as they mature.
Many palms and yuccas, as well as agaves, bamboos and banana trees, are perennials. They might not seem as if they should be, since they can grow so large. Spring bulbs are more recognizable as perennials likely because of their small size. Lavenders and some salvia develop more woody stems than banana trees. They are perennials nonetheless.
Perennials are proponents of sustainability.
Perennials are generally self-perpetuating. Lavenders and similarly twiggy sorts may not seem like they are, but they can be. Their lower stems that sprawl over the surface of the soil can grow adventitious roots. These adventitiously rooted stems can grow as new plants to replace the old. Herbaceous perennials are more overt about self-perpetuation.
Lily of the Nile, for example, constantly produces new rhizomes to replace the old. It can do so indefinitely. Some may have done so longer than the oldest bristlecone pines have been alive. They do not retain old growth as evidence of their age. This self-perpetuation is an advantage in home gardens. It facilitates both sustainability as well as propagation.
Lily of the Nile, Daylily, Kaffir lily and African iris are very simple to propagate by division. Once separated, either after bloom or while dormant, their rhizomes grow as new plants. Many perennials actually perform better after occasional division. It alleviates congestion by providing more space to grow and bloom. Canna and ginger rhizomes grow very fast. Canna may benefit from annual division.
Highlight: Lungwort
Its unappealing common name is less common than its more agreeable botanical name. Lungwort does not sound as pretty, or at least as official as Pulmonaria officinalis. It is an evergreen perennial, although its foliage likely desiccates through summer. New foliage replaces it during cooler autumn weather. Lungwort prefers cool and moist partial shade.
Mounds of foliar rosettes grow no deeper than a foot. They often stay only half a foot high as they spread as wide as two feet. Their lowest rhizomes produce adventitious roots so that they can sprawl even farther. Such growth is easy to divide. Foliage of most cultivars exhibits pretty lighter green or silver spots or blotches. Some is almost completely silver.
Lungwort blooms mostly for late winter and early spring. Trusses of daintily small flowers hover barely above their basal foliage. The most popular sort blooms with pinkish purple flowers that mature to blue. Others bloom with purple, pink, purplish red or white flowers. Although foliage is healthier within partial shade, sunshine promotes profusion of bloom.
Tony Tomeo can be contacted at tonytomeo.com.
