Aureolaria grandiflora in full bloom

Aureolaria grandiflora, the large-flowered yellow false foxglove, is now in full bloom. This species (C value of 8) is parasitic on roots of oaks and is a characteristic species of rich oak savannas. We introduced this about 10 years ago and it became readily established where planted and has now spread widely. The photo shows a rather large patch at the edge of an open savanna.

Although Aureolaria grandiflora is an obligate parasite on oaks, it does not do any harm to the tree. It primarily "infects" the tiny roots that are present under the drip line of the canopy.  

 It may seem odd to see this species in an area full of birches. Where are the oaks? However, if you start to look around you will probably see an oak grub or two. These small grubs are often years old, being burned back each year by our annual savanna fires, and readily support A. grandiflora.

According to greenhouse research by Musselman from UW-Milwaukee, seedlings never get past the cotyledon stage unless they infect oak roots. Although this species is often called a "hemiparasite", it looks like an obligate parasite to me. It is an interesting "obligate" however, since it does not destroy its host.

This is one of the showiest species in flower right now, and well worth seeking out in our ridge-top savannas.