While I was gardening

The art of gardening and the science of life.

“. . .why should that impress us? They can eat light, isn’t that enough?”*

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Stripes, spots, and swirls make up the patterns of the plant world.  Patterns in an array of color, shape, and size make their world richer than anything humans have yet imagined.  Upon seeing a plant with variegated foliage, the first question that usually arises is ‘Why?  Wouldn’t plain green be more useful?’.  That plants respond to their environment is not much debated, or shouldn’t be, at this point in our understanding of botany.  A plant with variegated foliage is better camouflaged in a setting of low or dappled light.  Difficult to identify and munch upon a leaf that blends into the shadows; a very beneficial adaptation for something that can’t get away from a threat.  Sometimes, variegation is a response to very specific light levels, and as a result, those plants may survive only in those specific conditions, but those conditions also support the plants’ coevolved predators.  This is most often seen in tropical, understory plants.  Variegation is sometimes the result of a virus the plant has contracted, and is attractive to the human viewer who propagates that plant.  But the stripes of Canna, the spots on a Trillium’s leaves, and the swirls on Calathea foliage are proof that plants do much more than just grow and ‘hope for the best’.  They outsmart predators by hiding in plain sight – and this is just one example of their ingenuity.

Many plants offer decorated landing pads and runways, tunnels and tubes, enticing aromas, and of course, a wide variety of color to make their flowers irresistible to the creatures they depend upon for reproduction.  Does this mean that flowers compete with each other to attract the most pollinators?   Appearances tell us so.  For example, some flowers are shaped to conform to the body of the insect that pollinates it.  Tube flowers with nectar far down at the base require the pollinator to enter the tube as deep as possible, therefore, ensuring that the most pollen attaches to the body of the insect as it exits the flower.  Some plants have developed flowers that look or smell like a female of the species of insect required for pollination.  A big tease, but it works.  More primitive plants, those pollinated by wind, haven’t developed such showy flowers.  Conifers and many hardwood trees, as well as grasses, sedges, and a few other plants, save energy by allowing wind to do the work of pollination.  No need to entice insects with color, shape, or fragrance.  These are ancient plant families, but by no means are they inefficient.  They produce vast amounts of pollen – much more than needed for the job at hand.  Their flowers tend to follow an easy pattern – long catkins or inflorescence that move easily and proficiently on the wind.  No unnecessary color, aroma, shape, or timing.  These plants compete by the simple process of mass-production.  That plants compete shouldn’t surprise us.  After all, we see competition throughout the biological world for many reasons – food, mates, and shelter top the list.  We all do it.  Why would plants be different?  Resources are limited but need is not.

Some plants have pared down reproduction to such an extent that they self-pollinate.  Most of these plants are annuals or short-lived ephemerals.  Some plants that self-pollinate have flowers that don’t completely open, thereby, not releasing pollen to the environment.  Other plants have developed flowers that are smaller and less showy than other plants, and their pollen is released near their stigmas.  No need to wait for a pollinator or a windy day.

All methods of reproduction that plants have developed contain disadvantages, but considering the enormous scope of hazards that plants face, these adaptations have proven creative, cunning, and highly successful.  And remarkable.  But the most astonishing aspect of plant life is their ability to photosynthesize – and we all know the by-product of photosynthesis.   So, we should be impressed; after all, plants hold the life of our planet in their leaves.

*Tim Plowman, Ph.D.

 

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Author: dphare2014

Horticulturist, Lead Steward Carkeek Park Demonstration Gardens, Author

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