Q:
Why do some perennial plants enjoy longer lives than others?
Sylvia Blum, Clarksburg, WV
A perennial's longevity depends on many variables including its genetic makeup and its environment.
Photo/Illustration: Melissa Lucas
A:
Leonard Perry, an extension professor at the University of Vermont, responds: The answer depends partly on the plant and its genetic makeup and partly on whether the plant’s cultural requirements are met. In nature, perennials have adapted to survive in specific habitats. This has affected their genetic makeup. For some, such as hollyhock and foxglove, this may mean a short life (two years), with survival through spreading seeds. For others, such as false indigo, hosta, iris, and peony, this may mean slow growth and long life (often 25 years or more).
It is important to place a perennial in a site to which it is accustomed to prolong its life, especially regarding light and soil type. If you place a plant in a climate or habitat for which it is not adapted, it may turn into an annual or short-lived perennial. Those that are adapted to harsh environmental conditions, such as drought or cold, will not fare well if planted in another climate. For example, tender perennials such as gaura and many salvias will have a shortened life (one year) in cold northern climates, as will cool-loving delphiniums in hot southern climates. If you place sun lovers, such as daylilies, in the shade, they may bloom less—if at all—or die out. By contrast, if you place shade-loving perennials, such as hostas, in the sun, their leaves may perish from sunburn.
The culture and care you provide a perennial can also affect its life. Stresses such as too little water (especially as plants are getting established), the wrong soil type, or the lack of division if needed can shorten their life expectancy. Spreading perennials, such as bee balm or mint, that are kept in a confined space, such as a pot or a hole in weed fabric, or that are covered too deeply with mulch will have a shorter life. Those that require well-drained soil, like lavender or Russian sage, will have a shortened life in wet soils. If you plant a moisture-loving astilbe in a dry site, it will die prematurely. In addition, stresses from wildlife, such as chipmunks and voles digging around roots or deer and rabbits browsing shoots, can also shorten the life of perennials, as can insects and diseases.
Paying attention to your plants’ cultural requirements and giving them the right growing conditions are the keys to extending the life of your perennials. Keep in mind, however, that many are tough, tolerating a range of conditions and care. As long as you avoid exposing them to extreme conditions, your perennials should last for many years, even in a less-than-ideal environment.
