As I wrote in an article about habitat restoration a few months back, over four years ago I stumbled upon this fascinating plant, Aureolaria grandiflora, commonly called large flowered false foxglove, growing on a savanna in southern Missouri.
At the time I had no idea it was a plant parasite, I simply admired its profuse bright yellow blooms which appeared in late July on the cedar choked savanna.
After completing the first steps to restore the savanna habitat around the plant specimens, I investigated this plant further in graduate school, in a project titled “Aureolaria grandiflora (Benth.) Penn. Response to a controlled burn, stratification, and presence of three species of Quercus.”
What is a savanna?
A. grandiflora is a common wildflower native to Ozark savanna habitats. Although glades are typically rocky dry upland south or southwest facing “miniature deserts,” savannas are upland open oak habitats where at least 50 percent of the sunlight is able to reach the forest floor.
Open oak savannas historically were maintained by regular wildfires, resulting in a scattering of fire-resistant oaks growing amidst a floor of grasses and forbs. Like the many glades and savannas in the Ozarks, the glade and savanna habitat where I did research had been overgrown with native eastern red cedar, shading out the forest floor, preventing the growth of nearly all native forbs which had been present in history.
Discovering A. grandiflora, which is an indicator plant of a historical savanna habitat which once existed prior to European settlement and wildfire suppression, growing in a break in the dense cedar canopy back in 2009 began my study of this beautiful wildflower and its suitable habitat.
What is A. grandiflora (large-flowered false foxglove)?
A. grandiflora is a plant in the Figwort family. It is a common wildflower found across the state of Missouri and is often found in dry upland woodlands in the Ozarks. It is a small herbaceous plant which can reach up to about 4 feet tall branching off of a perennial root crown called a caudex.
In July through September, it produces a beautiful display of yellow tubular flowers which are insect and other pollinator magnets, having observed honey bees, native bees and hummingbirds feed on the nectar from the flowers. Besides being a beautiful wildflower, it is also the host to the Baltimore checkerspot butterfly (Euphydryas phaeton).
What makes this wildflower so fascinating?
If it is not enough that it is a beautiful yet poorly researched wildflower, which survives in some very harsh growing conditions, A. grandiflora is also semi-parasitic to the roots of trees within the white oak group, including White (Quercus alba), Chinkapin (Quercus muehlenbergii), and Post oaks (Quercus stellata).
Typically found growing in proximity to their hosts, A. grandiflora produces its own chlorophyll but takes advantage of the large, deep root system of the oaks to obtain valuable water and nutrients. The roots of A. grandiflora form haustoria (modified root) connections to their host species.
Page 2 of 2 - In last year’s drought, these plants were some of the only green plants on the savanna. When we think of a parasite, we think of something harmful, but usually populations of A. grandiflora do not get large enough to cause harm to the white oak trees.
Some of our most beloved wildflowers, such as Indian paintbrush (Castilleja coccinea), and Wood betony (Pedicularis canadensis) are also, harmless plant parasites. Unlike Indian paintbrush, A. grandiflora is a facultative parasite, one which has been proven to survive without a host if given adequate nutrients.
A. grandiflora is a fascinating plant which I enjoyed researching throughout my time at Missouri State University. Part of my research was a greenhouse study which allowed me to see up-close the haustorial connections the plants have with their oak hosts.
From now until September, keep an eye out for this and other similar species of false foxglove, a stunning plant which has a unique underground relationship with its environment.