Milkweeds and Monarchs
It is such a fabulous time of the year in the gardens! The heat has finally stalled out (yeah!) and the gardens are lush and glorious. The highlight for me in the Ripley Garden is the diversity of birds, butterflies, bees, wasps and other creatures that bring the garden to life. Seeing numerous monarch butterflies in the garden makes my heart sing, since the overall population has declined in recent years due to habitat destruction and the subsequent loss of food sources.
Monarchs feed primarily on milkweed (Asclepias family). These plants usually like sunny, disturbed sites, so they are often found along roadways. The most frequent roadside milkweed is A. syriaca, a 3’-5’ tall plant which multiplies both by runners and by seed.
Unfortunately, roadside plants are often killed chemically or mowed down just as the butterflies are seeking food and nectar sources. Knowing the monarch population is in peril, I planted a variety of milkweeds in the Ripley Garden to nurture the population and educate my visitors about some planting options for their gardens.
There’s the readily available ‘Butterfly weed,’ Asclepias tuberosa, which blooms a vibrant orange color in June and July, sometimes repeating a bloom slightly later. For the most part, it is not in bloom when the adults are present and needing nectar. However, the adults do lay eggs on the foliage, and the emerging larvae will strip the plants clean rather quickly.
I also have Asclepias verticillata, a Midwestern native that is only about 1′-1.5’ tall, and spreads by underground stolons (horizontal runners) in dry rocky soils to form a colony. The white flowers are borne on the top of the stem in clusters.
Asclepias purpurascens, a real stunner blooming in early June with glorious hot raspberry-colored flowers, is another milkweed native to the U.S. that I am growing. It is quite rare in cultivation due to seed viability issues, but hopefully this will soon be solved. Since it is past bloom before adult butterflies appear, this milkweed does not serve as a nectar source for monarchs and I have not witnessed any larvae feeding on it.
The milkweed which seems to be getting ALL the attention of the monarchs in the Ripley Garden is… drum roll please…. Asclepias curassavica. This plant is native to South America and is hardy only in plant hardiness zones 9 and 10, though it has spread and established throughout tropical regions. In Washington D.C., the plant sows by seed from year to year. The plants will reach anywhere from 1’-5’ tall, and thrive best in full sun with average moisture.
Asclepias curassavica is a tropical milkweed which produces blooms of brilliant oranges and reds between June and October, so it provides both nectar for adults and food for caterpillars. Many of the plants in the Ripley Garden are totally bare, just a stripped stalk remaining after some very hungry caterpillars have devoured everything they could munch. When the time is right, the caterpillars find a secure place where they can hang freely and create a chrysalis.
I allowed the Asclepias curassavica to selfsow in an area up against the Arts and Industries Building, and have been delighted to see a number of caterpillars munching away. But I wasn’t finding any chrysalises, until recently. Hiding in plain sight, the caterpillars climbed up the brick wall to transform while hanging in the window wells!
In this window well alone, there are four chrysalises that have not pupated, and three remnants where butterflies have already emerged! The more I started looking, and really seeing, I realized that I created a perfect nursery for the monarchs, without even trying!
I am so delighted that the monarchs, and a plethora of other insects, call the Ripley Garden home! Your garden can also be an ideal butterfly habitat. Avoid the use of toxic chemicals (this includes mosquito sprays!) and plant a wide variety of plants known to be beneficial to insects. Plant it and they WILL come!
– Janet Draper, Smithsonian Gardens Horticulturist