Buchus: The Scent of the Fynbos

After our exam on August 1^st, I attended a plant ID walk on Buchus (boo-koo-s) featuring Roger Oliver. Roger is one of the horticulturist that is curating part of the fynbos collection. Specifically, Roger specializes in Pelargoniums and Buchus. In this walk, we broke down and dissected the buchus into their specific genomes and identified some specific samples present in the Buchus Garden.

First off, Buchus are native shrubs that are in the Rutaceae family, commonly known as the citrus family. Indicators of this family include glands under the leaves (may be too small to notice) and unique fragrances amongst the species. When you chew the foliage, the glands produce a mucus-like texture in your saliva.The fruit of buchus resemble a miniature buddha’s fingers, also known as a citron. A 5-horned amoeba-like fruit with glands that secrete a strong scented oil from the leathery rind. In the picture below, you can observe both features. 

There are six primary genomes grouped into the buchus category including: Agathosma, Adenandra, Acmadenia, Coleonema, Euchaetis, and Diosma. To identify which genus a plant is, it is imperative for it to be flowering.

For the genus Agathosma, the superior ovaries sit inside a deep cup-shaped nectar disc. These plants also have styles protruding out of the cup and flower. It is the only Buchu possessing styles longer than the petals. Below is a photo of the flower I dissected to show these characteristics.

Adenandras and Acmadenias are very similar. They have minute differences though. Both have single-few flowers at the apical tip of the branches. The reproductive features of these flowers sit inside the calex which generally produces a hairy throat. The difference between the two where the nectar glands are located. Acmadenia species only have glands on the stamen, whereas Adenandras have them on both male and female structures. I really wasn’t able to see this. It is probably visible with a hand lens. Instead, I distinguish the two by looking under the petals. Adenandras possess a pink/red tip underneath. The white flower below is an Adenandra, and the pink is Acmadenia. Unfortunately, I don't have a clear picture of the colored tips of an Adenandra, but you can kind of see some discoloration in the photo.

The Coleonemas are easy to identify because they have a very soft foliage and tiny flowers. I think these flowers are pretty neat to identify. The key to Coleonema flowers is in the stamen locations. You can notice that the stamens are situated in grooves between the petals. Super easy to distinguish.

Lastly, Euchaetis are the buchus with petals creating a long, hairy throat. Like the others, the style stays inside the flower.

We did not dissect or look at the Diosma genus, but I can tell you that the defining characteristic is the shallow, undulating nectar disc surrounding the ovary. These plants also have fruits with long horns.

Here is my list of the Plants I need to memorize for my exam on August 15^th:

·         Agathosma crenulata

·         Agathosma ovata

·         Agathosma ovata ‘Outeniqua’

·         Agathosma ovata ‘Kleitjieskraal’

·         Agathosma mucronulata

·         Agathosma apiculate

·         Agathosma capensis

·         Agathosma serpyllacea

·         Acmadenia mundiana

·         Acmadenia heterophylla

·         Acmadenia obtusata

·         Adenandra gummiflora

·         Coleonema pulchellum

·         Coleonema album

·         Diosma hirsute

·         Euchaetis meridionalis