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BOTANY 101

You Only Bloom Once … or Twice … or More The lives and times of annual and perennial plants by Daniel Murphy H IGH I N TH E W H ITE MOU N TA I NS OF CA L I FOR N I A L I V E S A V ERY OL D TR EE . Now over 5,000 years old, this Great Basin bristlecone pine has a long story to tell. Meanwhile, Eurasian thale cress goes by the nickname “fruit fly of the plant world” for its ability to complete its entire life cycle in a few short weeks. Disparate life histories such as these are just one of the many things that make plants so fascinating. Avid gardeners are well aware of the various life cycles of certain plant species. In planning our gardens, we know that the annual plants we place in our beds are temporary, while some of our perennial plants could easily outlive us. In some instances, plants that would otherwise be perennial in their native range are treated as annuals, succumbing each year to the freezing temperatures of winter. In the wild, plants have a variety of strategies for enduring diverse environmental conditions. How long they take to complete a life cycle is just one of these strategies. Plants that complete their cycle within a year’s time are considered annuals. They are also monocarpic, meaning they flower once and then die. Winter annuals germinate in the fall, then flower and set seed the following spring; stiff greenthread (Thelesperma filifolium) is one example. Summer annuals, such as common sunflowers (Helianthus annuus), sprout 8 | W I L DF LOW E R

during warm months and have matured by the time cool weather returns. Annual plants are commonly found in areas that experience regular disturbance (such is the case with bluebonnets and Hill Country pastures) or where environmental conditions are unpredictable. A significant portion of our common weeds are annuals, as are numerous desert wildflowers. The extensive seed bank they maintain in the soil allows them to persist long term. By staggering the years in which their seeds sprout, annuals ensure the survival of their species — a strategy ecologists call “bet hedging.” Most plants are perennials, going on to live year after year and — in most cases — producing seeds numerous times throughout their lives. During times of the year when conditions are not conducive to growth, such as the frigid months of winter or the hot, dry days of summer, perennial plants can go dormant. Their foliage may die back while they wait things out as roots

Profile for Lady Bird Johnson Wildflower Center

Wildflower Magazine 2019 | Volume 36, No. 1  

Flower-dwelling predators, love letters to native plants, how to bring nature play home, discovering a rare morning-glory, remembering an in...

Wildflower Magazine 2019 | Volume 36, No. 1  

Flower-dwelling predators, love letters to native plants, how to bring nature play home, discovering a rare morning-glory, remembering an in...

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