I found these plants on an unusual patch of yellow sand in Dryandra Woodland Candy Block that has Drummond’s Mallee and a large number of shrubs. In August I noted a low compact plant with lovely foliage that I called “carrot plant” while waiting for it to flower. Flowers in late October revealed it to be an uncommon species, Petrophile circinata. Circinate means curled around itself, presumably referring to the whorled leaf arrangement. Images below show the plant and flower.
As this species was coming into flower I noticed that there were a few very similar plants that had beautiful hairy red growth appearing on what I thought were dead flower stalks.
Gadzooks! The local experts were confounded until the growth expanded into the flower of slightly later flowering Isopogon villosus (villous means hairy with long soft hairs). The flowers emerge from thickened scaly clumps of old growth.
To my uneducated eye, vegetative growth of both species is similar, but Petrophile circinata leaves are a slightly darker green and leaf petioles have a distinctive linear fold in the petiole stem.
I usually have no problem distinguishing Isopogons (smooth fruiting nut) from Petrophiles (scaly nut), but these squat species are a real challenge. After a fair bit of excavation in the prickly growth I eventually found a rather confusing nut on the stem below the flowering clump.
The slideshow below follows both species as they flower.