Double Trouble

Visit any of your favorite garden centers and you will see new introductions of old familiar favorites.  For instance the purple coneflower is no longer purple.  It comes a range of colors from red, yellow, orange, green, and white.  You will even find cultivars where the traditional cone has been modified into flower petals often called double flower.

There is nothing wrong with new introductions.  The plant has been selectively introduced with characteristics that are desirable such as disease resistance, prolonged bloom time, and tolerance to growing conditions, and double blooms.  However, when we take a closer look at modifying the flower to become a double we lose some unseen attributes.  To make those extra flower petals stamens and anthers that support and provide pollen have been modified into petals.  These modifications might seem harmless unless you are an insect looking for food.

Besides losing the pollen the extra petals add depth to the bloom.  This isn’t something that you normally think about until you are trying to reach for nectar.  It’s almost like a kid reaching for the plate of cookies on the counter that is just out of reach.  Native pollinators have coevolved with our native flora.  Their body structure, mouth parts (including tongue) are the perfect length to access what they need.  When we start to modify plants subtle morphological changes are made that could potential impact insect health.  Increase flower depth also requires the insect to work harder and expend energy to gain access to nectar if available.  This extra work can impact the foraging capabilities of the insect requiring it to spend more time at each flower.

We are all plant enthusiast and often get caught up with new introductions.  We support the idea of including new introductions into the garden but we encourage you to take a good look before you plant.  Do the new introductions have attributes that make it a win-win?  Besides bolder and brighter colors do they still provide for the insects that visit them?  None of us will be able to know how many µl of nectar is being produce nor will we know the protein content of the pollen.  However, we can easily see if the flower will be a double bloom.  If it is there is a strong likelihood that the essential elements that insects need have been modified and no longer present.   We encourage that double flower plants are not the dominant flower in the garden but used as a specimen or an oddity.

Scott Evans
Scott Evans is a horticulture assistant with Nebraska Extension in Douglas-Sarpy Counties. A certified arborist through International Society of Arboirculture and Nebraska Arborist Association. Scott is also Tree Risk Assessment Qualified through ISA. Scott co-leads the Master Gardener program in Douglas & Sarpy counties. Along with volunteer management he provides his expertise with disease and insect identification, lawn and landscape weed management, plant health, and I.P.M. practices. He also enjoys growing many houseplants ranging from African violets to cacti and succulents. Scott has two Bachelors of Science, one in Biology (emphasis in Botany, Ecology and Environmental Science) and second in Environmental Geology from Northwest Missouri State University. He earned his Master of Agriculture from the University of Nebraska-Lincoln.

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