Thematism in the Interior Landscape

“Humanity is exalted not because we are so far above other living creatures, but because knowing them well elevates the very concept of life.”

     -E.O. Wilson

One of In Situ’s primary goals as a company is to increase interest in plants in order to reconnect people to the natural world. We believe strongly in the hypothesis of biophilia, first conceived by the venerable E.O Wilson; the human need to commune with other living things. We feel as though this is why people have always kept plants indoors, and that now more than ever it is important to continue the relationship.

We use several strategies in order to further this goal of increasing interest in plants: making use of the wide variety of less-often used species is a good example, as the visual impact is immediate and apparent. Beyond plants’ appearances, however, lies the really fascinating stuff, and this is what we like to bring to light in our designs.

Cyclosephala colasi on a Philodendron inflorescence. Photo © Marc Gibernau/Denis Barabé; retrieved from the International Aroid Sciety website.

Cyclosephala colasi on a Philodendron inflorescence. Photo © Marc Gibernau/Denis Barabé; retrieved from the International Aroid Sciety website.

Even the most commonplace species can hold fascinating features when they are brought into context. For instance, the humble Philodendron, long a staple of interior landscapers, has a unique aspect to its physiology. The inflorescences (flowers) of many species are thermogenetic: they produce heat. And quite a lot of it, as well: some species’ inflorescences can rise 10°C above ambient temperature! This interesting adaptation serves to volatize aromatic compounds that attract pollinators, of which beetles are usually the primary ones. See here to read more about thermogenesis in plants.

The above is just one example of the countless facets through which one can look at plants. There are many themes which we have explored; below are but a few.


Plants' natural habitats are, particularly in the case of the tropics, richly populated communities of species, with many growing closely around (or on, or in) each other. These ecological landscapes are referred to as biotopes, and these are interesting themes to explore, as they offer us a (somewhat stylized and selective) glimpse into where these species are from. To actually see these habitats in person is incredible, and we want to share this with our clients. Using solely plants from a particular region can highlight, for example, an area under grave threat of deforestation, highlighting the need for conservation.

Natural Variation within Species

The world of plants is one of incredible diversity, and even within species, an incredible amount of variation can be seen (see this post for more thoughts on this). Another perspective on this variation is convergent evolution, in which completely unrelated species evolve similar forms to solve the same problem. For example, many of the Euphorbia species from Africa and Madagascar often look for all the world like cacti (which are only present in the Americas), but are from a completely different family. These disparate species have come upon similar means of water storage (water-holding stems) and self defense (spines) that allow them to exist in some of the harshest habitats on earth.


The epiphytes include many of our favourite plants, and many species which people are used to seeing in pots actually spend their entire lives without ever sinking their roots in soil. Orchids and Tillandsia bromeliads (the now very popular ‘air plants’) are some of the more commonly recognized ones, but the vast majority of tropical plant species are in fact epiphytic. Some of the more common epiphytes available are lipstick vines and goldfish plants (Aeschynanthus spp. and Columnea spp., respectively), begonias, many aroids such as Anthurium and Philodendron, and many ferns. Using exclusively epiphytes together allows us to see the richness of these plant communities living far from the forest floor.

The Carboniferous garden: Afrocarpus gracilior, Zamia furfuracea, Asplenium  nidus, Microsorum pustulatum and Psilotum nudum. Image © In Situ Plants.

The Carboniferous garden: Afrocarpus gracilior, Zamia furfuracea, Asplenium 
nidus, Microsorum pustulatum
 and Psilotum nudum. Image © In Situ Plants.

The planting pictured here is a good example of how we are able to execute the types of themes we explore, and also of how we, too, learn something new about plants nearly every day. We really wanted to make use of a particular tree, Afrocarpus gracilior, (also known as the Weeping Podocarpus), as the texture of the foliage and its dense, shaggy habit makes a really dramatic statement. It is also unique in that it is a tropical conifer, distantly related to our familiar spruce and pine. This group of plants, the gymnosperms, does not produce flowers, though it does produce seed, and arose during the Carboniferous period of Earth`s history, some 300 million years ago. It is this latter fact that we decided to explore for this planting.

The Carboniferous is so named due to the fact that this is when the great forests that were destined to eventually be swallowed by the ocean and preserved in the familiar form of coal were at their peak. It would have been a different landscape than the one we are used to today, for flowering plants had not yet evolved, and more simple plants dominated the prehistoric flora. Among these were the simple vascular plants which reproduce via spore such as ferns, tree ferns, and allied families, and the first seed-producing plants, of which A. gracilior is one.

Another primitive plant which produces seed but no flowers is Zamia furfuracea, also known as the cardboard palm. This is a cycad, related to the more commonly seen Cycas revoluta or sago palm. This plant was definitely a candidate for this installation, and its coarse texture and olive colour contrasted perfectly with our Podocarpus.

We had to represent the family of ferns in this planting (being one of the dominant flora of the Carboniferous), and chose two that highlighted the extraordinary diversity of form seen in these plants. Asplenium nidus, the birdsnest fern, with its rosette form of bright green, undivided fronds, is an epiphytic fern that grows on trees in Australasia.  Microsorum pustulatum, the kangaroo fern, takes another approach to its growth: it creeps along on a hairy rhizome, from which emerge deep green, incised fronds which are more classically ‘fern-like’ than A. nidus.

One final plant was used in this installation: Psilotum nudum, the whisk fern. This species was chosen more for its story than for its form, which is nevertheless an attractive bunch of semi-erect stems, from which are produced spherical synangia, which contain the spore the plant uses to reproduce. The species has no leaves, no roots, and only half a vascular system, and is very primitive indeed in its physiology, and was a must-have for this planting. What we discovered in our research, however, was that there is some evidence that suggests that P. nudum may actually be descended from more complex fern species, and that it may have reverted for some reason to this very simple form. Perhaps we will never know for sure, but P. nudum is definitely a great representative for other similar species which were prevalent during the Carboniferous.

These themes tend not to be immediately apparent to the casual observer, of course, unless the plants are unified by a physical characteristic, and so the obvious question is why bother? We are able (and would be more than happy) to produce educational signage for anyone who wishes to show off the subtleties of their interior landscape, but we feel that with this much intent in our work, there will be a mood created which is tangible, and which adds depth and value to our landscapes. We hope to draw the viewer into our world and experience plants on a new level, and to connect them with a world most urban residents would never encounter otherwise.