The golden yellow heads of Leucadendron, conebushes, are easy to identify, but the species can often be a challenge to separate. A key character in narrowing down the options is the size of the colourful leaves that surround the flowerhead. One of the species with comparatively large flowerheads is Leucadendron microcephalum. It is a peculiar species name as “microcephalum” means exactly the opposite: small headed.
The species was described by a French botanist Michel Gandoger in 1913. However, before he recognised it as a species, he considered it just a form of a more widespread species: Leucadendron decorum. That species, now known as Leucadendron laureolum, has larger flowerheads (up to 27mm long) than Leucadendron microcephalum (±16mm long). Therefore he described the form as Leucadendron decorum forma microcephalum to emphasize the difference. Upon recognising it as a distinct species, he reused his form name even if it was not now so appropriate.
Two other species also occur at Phillipskop with similar sized floral leaves (8-10cm long, 1.5-2.5cm broad): Leucadendron laureolum and Leucadendron gandogeri, the species named after Michel Gandoger himself. Leucadendron microcephalum however is easily distinguished by the unusual nature of the bracts that surround the developing cones. While all the species have these basal bracts, in Leucadendron microcephalum they are relatively large and noticeable. But what makes them stand out is when in bud they are covered with a sticky brown gum. This gum rubs off on unfortunate creatures that get too close. Rub your finger across it and it looks like you have been smeared with boot-polish. This character is found in no other species of Leucadendron and so Leucadendron microcephalum belongs in its own section, Brunneo-bracteata, the oil-bract conebushes.
The purpose of this brown oily covering is not known for certain but it probably protects the cone and developing seeds from insects. The seeds of Leucadendron are comparatively large for fynbos plants and hence provide plenty of nutrition for insects. It is not unsual to find cones of the protea family with grubs that develop inside them, feeding off the developing nuts. By covering the outer layer of the cone with this brown sticky exudate, it would deter any insect from laying its eggs inside the developing cone, thereby protecting the seeds from predation in this way. The seeds of Leucadendron microcephalum are also distinctive in that they have an irregular double-ridge on one side of the nut. It also does not have the broad thin wings of the other two species.
While the brown oily bracts help to distinguish Leucadendron microcephalum, the other two species are more challenging to separate. Indeed, they are even known to hybridise with each other, as well as with the smaller leaved Leucadendron xanthoconus, creating a range of intermediate plants. The most noticeable character to separate them is that the flowerhead of Leucadendron laureolum is usually hidden by the large flowerhead leaves, whereas Leucadendron gandogeri the flowerhead leaves are spreading and the flowerhead itself is easily visible. The identity can then be confirmed by looking at the basal brown bracts beneath the flowerheads, which in Leucadendron laureolum have minute hairs on the margin, whereas in Leucadendron gandogeri the margins lack hairs.
All three species have ranges that overlap to a considerable degree. Leucadendron laureolum is the most widespread, from the Cape Peninsula to the Riviersonderend Mountains and south to Cape Agulhas and De Hoop. Leucadendron microcephalum is found from the Kogelberg to the Riviersonderend Mountains, Phillipskop being on the edge of its south-eastern range. Finally, Leucadendron gandogeri occurs from Kogelberg to Bredasdorp. They can also be found in very similar habitats, on dry rocky slopes of the Cape mountains, although Leucadendron laureolum has a particular liking for deep sands at lower altitudes too.
