Gardening in the Shoulder Period

by Katherine King, Intern

Katie was recently chosen from eight finalists as our 2010 intern, sponsored by the Rotary Club of Shades Valley. From Bristol, Tennessee, Katie is a recent graduate of Samford University with a B.S. in biology--she has even studied botany in Belize (are you as jealous as we are?)! The internship gives a rising senior or recent college graduate hands-on experience with greenhouse production, planting, grounds maintenance, arboriculture, pest management, curatorial aspects of plant collections and garden display/design.

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Between the intensity of spring flora and the beginning of summer bloom, there exists what is sometimes referred to in the garden as the “shoulder period.” Compared to spring and summer, fewer plants are in bloom during this time of the season. As a newly graduated biologist (and aspiring botanist) and summer intern at Birmingham Botanical Gardens, an assignment was given to me to research native southeast wildflowers blooming within the shoulder period to plant in the Kaul Wildflower Garden.

Understanding this concept and learning which plants bloom during the shoulder period will help you add color to your plantings during what would normally be a “down time” in the garden.

In turn, I am attempting to catch up with the new Kaul Wildflower Garden curator’s vast knowledge of scientific plant names (he makes it up as he goes!) and help you add a little vibrance to your garden.

Asclepias tuberosa (butterfly weed) is a distinctive wildflower difficult to mistake, with its bright orange inflorescences and thick alternate leaves (the image to the right is courtesy of Northwest Ohio Nature©). This species is native to well-drained, sandy soil or upland woods of New Hampshire to South Dakota, and south to Arizona, Mexico, and Florida. They grow up to 3 feet in height in sun to partial sun.

Pollination of the Asclepias genus is strikingly remarkable. The petals of each flower form a hood with an outstanding horn in the center. As an insect lands looking for nectar, it often falls into the waxy hood, becoming trapped by the corpusculum (a structure at the base of the flower), which closes on the insect’s foot or proboscis. As the insect fights to free itself, it releases two pollen sacs (pollinia) attached to a sticky structure called a translator. After the insect frees itself, the translator dries and orients the pollen sacs to fit perfectly into the stigma of the next flower. Next time you are sneaking up behind a butterfly perched on a milk weed or butterfly weed, remember it may be momentarily ensnared.

Other native wildflowers blooming during this period include: 

• Echinacea purpurea (purple coneflower) – a common garden plant which grows well in moist to moderately dry soil, and is an excellent shade-tolerant plant. The rays are typically a dark rose color although may rarely be white.
• Stokesia laevis (Stoke’s aster) – are beautiful, light purple pin cushions of petals surrounded by delicate rays and are fairly drought-tolerant and shade-tolerant.
• Silene virginica (fire pink) – the bright petals of this flower catch the eye from a distance and grow wonderfully in rock gardens or sandy banks. They self-sow well with the help of hummingbirds or bees.
• Spigelia marilandica (woodland pinkroot) – this unique crimson flower with a yellow interior grows well in sun and shade in moist to moderately dry soil. They grow best in drifts of their kind, and take two years to become sizable plants.
• Tephrosia virginiana (goat’s rue) – yields a toxin that is poisonous to fish and was utilized by Native Americans, but beyond that, the perennial holds out in tough, dry sun or shade, and grows well in sandy or rocky soil as well as dry clay.