Platycerium bifurcatum

The staghorn fern

This month’s plant is one I don’t actually have in my collection. Not for lack of trying, though. Platycerium bifurcatum are fascinating in their care, morphology, and… behavior, but can present unique challenges as houseplants. And in the wild, new studies of their lives are changing the ways we think about plants.

Also known as staghorn ferns or elkhorn ferns, Platycerium bifurcatum are native to Java, New Guinea, New South Wales, Queensland, and Lord Howe Island and are members of a unique group of plants called epiphytes. Epiphytes live on other plants, but not as parasites. They use other plants for structure, but don’t take nutrients from it, those they get from the air and water around them. It’s an incredibly austere lifestyle that usually requires some special adaptations.

First let’s talk about what the staghorn fern looks like, because it’s not like any fern you’ve ever seen before. Staghorns, and other ferns in the Platycerium genus, all have two different kinds of fronds. One type is the nest or shield frond. This frond is usually round, flat, and attaches to the tree it’s growing on. The plant’s roots lie underneath the shield frond and are protected from wind and sun, so they don’t dry out. The second type of frond is the strap, or antler frond. These shoot out from the base of the shield and serve a few functions. They are reproductively active, perform photosynthesis, and also help to funnel water to the shield leaf and the plant’s roots. Here’s a picture of a mounted staghorn.

Aside from labeling the parts of the plant, this image also shows one of the challenges of growing staghorn ferns as houseplants. While they can be grown in a container, they are much more likely to thrive mounted to a wall like this one above. While this alone can be a challenge, staghorn ferns grow in colonies that can get quite large, like this one below that I found on Pinterest, stranger for scale.

Here’s another Platycerium, the P. superbum, just for fun. I found this one on a cool website called Daves Garden.

So you can see, these are not necessarily plants for the apartment dweller, like myself, but they are really incredible, and I had to devote a month to them.

But back to P. bifurcatum and the recent studies surrounding it. Kevin Burns, professor of biology at the Victoria University of Wellington, New Zealand recently published a study claiming that the staghorn fern is eusocial. This is a pretty big claim. Eusocial, meaning “truly social” is a term generally applied to critters like bees, ants, and termites. Animals that live in societies where some forego reproduction and perform other duties instead, for the good of the colony. There are three criteria that a lifeforms must meet before they can be considered eusocial, these are: overlapping generations, members who care for young that might not be theirs, and members who work for the group, but don’t reproduce.

Mammals are generally not considered eusocial because even in groups, all members tend to reproduce. In fact that’s usually the driving force behind a mammal’s existence. Whether or not humans are eusocial is something that’s up for debate, but we’re here to talk plants. In Professor Burns’ study he states that P. bifurcatum’s colonies qualify as eusocial. Plants working together to stay alive? Maybe? Let’s look at his evidence.

Professor Burns says that plants in staghorn fern groupings exhibit different structures based on their position in the colony. Plants at the top of the colony grow upright antler fronds with gutter-like channels for directing water to fan-shaped shield fronds suited to collecting it. Ferns at the bottom of the colonies produce clasping shield fronds and more pendulant antler fronds. The shield fronds at the bottom are also more absorbent. Thus, the bottom ferns seem to be built for structure and storage. Professor Burns has also shown that only some members of the colony reproduce and that generations do overlap.

Here’s a picture from Professor Burns’ paper highlighting the differences in colony members’ structures.

So are these plants eusocial? The scientific community hasn’t come to a consensus, more study is required. One question that needs answering is care of young. Can Professor Burns show that these ferns care for young in the group? It’s an incredibly interesting question and I for one am going to be following this study.