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The Importance of Being Ephemeral

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The first daffodils are peeking through the soil, and some of the earliest bulbs—crocus and galanthus—are finishing up their flowering cycle.  As spring progresses we will watch the annual parade of our favorites:  tulips, allium, eremurus, and others will flower and vanish before the worst of summer heat. 

Denver is a great place to grow ephemeral plants of many kinds because the harsh seasonality it experiences annually is the sort of thing that drove the global evolution of ephemerality in the first place.  Bulbs and their morphological cousins, rhizomes, corms, and tubers, are designed for storage.  In steppe climates across the world with pronounced dry and wet seasons, such storage systems are vital and allow plants to occupy environments that are only favorable for a short time each year.  Plants with such structures furiously produce carbohydrates when water is plentiful, sending them down the stem to be hidden underground through the hard times of drought.  Fewer predators can find the reserves underground, though it isn’t fool-proof (just think of the fun squirrels have digging up garden bulbs!).

Because they grow underground, bulbs, corms, rhizomes and tubers are often all thought of as roots, but only tubers actually arise from root tissues.  Corms and rhizomes are modified stem tissue, and bulbs are actually leaves!  The variety of structures all filling the same role throughout the plant kingdom is evidence of the success of ephemerality for growing in difficult places--it has been "thought of" more than once.  

Not all plants with storage organs are from the steppe or desert.  Some woodland favorites like anemones and dicentra also rely on underground storage.  In forests the problem ephemeral plants face is not usually drought, but an excess of shade in the understory—woodland ephemerals take advantage of the sunlight that reaches the forest floor before deciduous trees have leafed out.  Later in the summer when light reaches the forest floor less reliably they return to dormancy to await the next spring. 

Ephemeral plants provide a feast for our eyes in the spring, and an early feast for pollinators.  Although their visible charm is short-lived, they’re always there, just waiting for the right time to bloom again.

This post is part of a series, “Four-Minute Ecology.”  New columns are posted every other Tuesday.

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