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.
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.

“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.

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 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.

Selaginella uncinata. Image © 天問 小窩; retrieved from Wikipedia
Selaginella uncinata. Image © 天問 小窩; retrieved from Wikipedia
Elaphoglossum metallicum, another iridescent plant. Image © In Situ Plants
Elaphoglossum metallicum, another iridescent plant. Image © In Situ Plants

Iridescent plants are a welcome addition to the interior landscape: who wouldn’t want a shimmering blue plant in their presence? There are several species (most only marginally available in cultivation) that exhibit this exciting type of colouration; Selaginella uncinata is perhaps the most available, under the name peacock spike moss. It can sometimes be found at garden centres and the like, and is produced by Exotic Angel Plants, amongst others.

I recently read an interesting article in The Scientist magazine on natural iridescence which explained something fascinating: iridescence is not caused by a pigment or a dye, but a structural property of the leaf (or wing, or feather, or whatever). Textures of the tissue surface are covered in ridges, bumps and dimples that refract the light in a way that appears to us as a metallic sheen. This adaptation is thought to have arisen during the Cambrian Explosion, as creatures were developing the first primitive eyes able to sense light, dark and contrast.

In cultivation, plants known for iridescence such as S. uncinata can show more or less of this colouration under different cultural conditions: I find that the best conditions for S. uncinata are moist, shady and humid (my default conditions for the genus). In bright light, this plant will blush pinkish-red, which can create a spectacular effect coupled with the iridescent blue, though it is a fine line to achieve both and maintain both colours. Apparently the ratio of red to far-red light makes a large difference in the production of iridescence, at least in the related species Selaginella willdenowii., though that`s somewhat outside the realm of the casual grower to play around with.

But perhaps the most intriguing aspect of this whole thing is the why: what evolutionary benefit do plants gain from this colouration?  A paper published in the Journal of the Royal Society suggests two possible advantages: the iridescence may act as a deterrent to herbivores, as the (seemingly) constantly changing shape would not allow herbivorous insects, for example, to develop a search image (a familiar shape which the insect recognizes as a food source: search images abound, in our own minds as well as those of insects). The other possible advantage is that the iridescence (which is primarily seen in shade-dwelling plants, as I mentioned earlier) can prevent damage from exposure to too much light, say from a newly created hole in the canopy overhead that permits direct sunlight to reach the forest floor.

Whatever the reason, these plants hold a special fascination, and they are beautiful to behold. With a little care, these can make incredible additions to anyone’s indoor garden (and outdoor garden, if you are fortunate to live in a place with mild enough winters to get away with it).

Unknown Phalaenopsis hybrid. Photo © Arad; retrieved from Wikipedia
Unknown Phalaenopsis hybrid. Photo © Arad; retrieved from Wikipedia
In Situ Plants interior landscapes, vertical gardens, and other plant installations in Toronto
Bulbophyllum 'Elizabeth Ann Buckleberry', probably one of the most commonly grown plants in the genus. Photo © Ed M.; retrieved from The Orchid Source

Did your eye even register the photo to the left? You can be forgiven if so: a beautiful sight it might be, but the now ubiquitous Phalaenopsis has become such a commonplace sight in homes and commercial settings that it’s nearly impossible now to regard them as the spectacular plants they are.

Tissue culture, offshore production and improved shipping techniques seem to have contributed most to the availability of these plants at nearly any place that sells plants (and quite a few that don’t): the US imported an estimated 400 40-foot containers of Phalaenopsis in 2010, and that number has surely risen since then. The plants are then forced into flower in greenhouses and then make their way to the mass market a few short weeks later. (This hasty method of production, though certainly bringing production [and thus retail] costs down, can also produce plants which may not perform as well after they leave the greenhouse, but that is a whole other post for another day.)

But why has Phalaenopsis become the poster child for the entire orchid family? After all, there are more than 26,000 species of orchid worldwide (many of them, admittedly, not suitable for culture, such as this exceptional species). Phalaenopsis was already being grown as a cut flower, which made it a good candidate for the early research into commercial production, and it is a very easy plant to grow commercially, growing rapidly and flowering reliably under the right conditions.

I don’t really have anything against Phalaenopsis in particular: there are over 60 species in the genus (check out the photos here), to say nothing of the countless hybrids therefrom. I’m definitely glad that more people are trying these plants out and having success with them. But it just seems a shame that the full diversity of orchids isn’t well represented in the mass market. The whole charm of orchids, after all, is their exoticness, and it certainly gets a lot more exotic than Phalaenopsis.  Even other commercially produced genera offer a little more curiosity, and these are often easier of care for the novice than Phalaenopsis, and can also have more unique foliage so that they hold visual interest when not in flower.

It doesn’t seem as though the humble Phalaenopsis is going anywhere any time soon. Perhaps the best we can hope for is that other species become equally well-represented in commercial production. And my personal hope is that many species become so well-represented: the Orchidaceae really are incredible, and everyone should have the opportunity to try growing something a little different.

The world of plants is one of staggering variety: to date there are around 400,000 species known to science, with many more waiting to be discovered. An interesting facet to this variety is the fact that there can be incredible diversity within species themselves, such that different individuals of the same species growing side by side might not be immediately recognizable as being at all related.

Oftentimes, a variety will supercede the parent species in popularity, perhaps because it performs better in cultivation or has a more interesting appearance, and becomes used more often than the ‘original’ species. (Note that I am not discussing man-made hybrids or cultivars here- that is a subject for another time.)  A perfect example is Dracaena fragrans ‘Massangeana’, which sports a pale green stripe down the center of its leaves not present in the typical D. fragrans. One doesn’t even really see the boring old D. fragrans anymore, so popular has its variegated variety become.

But would the effect of ‘Massangeana’ not be greater if it were a single specimen amongst several of the regular D. fragrans? After all, that’s how one would find such a variety in nature: they would stand out like a sore thumb, and perhaps even give taxonomists a run around thinking it might be a different species. I think it would, and so that’s what I do with these types of plants.

I believe that, rather than leaving these varieties to stand alone as representatives of their species, they should be incorporated and used (sparingly) with their parent species to highlight and exemplify the fact of their origins, and to allow people a glimpse at the near endless variety of the plant kingdom.

A. peruvianum gametophytes, in a somewhat underwhelming photo. Image © In Situ Plants.
A. peruvianum gametophytes, in a somewhat underwhelming photo. Image © In Situ Plants.
Closeup of Adiantum peruvianum showing sori. Image © In Situ Plants.
Closeup of Adiantum peruvianum showing sori. Image © In Situ Plants.

I recently noticed, to my great excitement, that some fern spore had germinated in one of our vertical gardens. In this case the species in Adiantum peruvianum, the Peruvian maidenhair fern, a delightful species with unusually large pinnules (leaflets), and which eventually grows fronds a metre long in ideal conditions. When this species was planted, the fertile fronds were already showing the sori (clumps of sporangia which produce the spore) along the margins of the pinnules, and I had hoped (and had really thought it was against the odds) that some of the spore would in fact do its thing in the garden. Lo and behold, here we are.

You may know that the ferns are a fairly primitive group of plants that were on earth a million years before the dinosaurs, having only a rudimentary vascular system and never having developed flowers or seeds. In the right conditions, propagation by spore seems to be an extremely effective means of reproduction, provided a few basic needs are met.

In flowering plants, a seed produces a plant which grows to maturity, produces male, female or dioecious (male and female) flowers, pollinates and/or is pollinated, and the pollinated flower then produces seed to complete the cycle. In ferns and other spore-producing plants (mosses, liverworts and tree ferns), spore germinates and produces a gametophyte consisting of a single simple leaf called a prothallis. It is the gametophytes which do the reproducing in these plants: the male organs of the gametophytes release sperm, which, dependent upon the presence of a film of water on the surface of the growing area (certainly one of the reasons why these plants are usually restricted to moist, humid environments), travels between gametophytes and fertilizes the female organs. At this point a new plant is produced which is immediately more recognizable as a fern, and which will reach maturity and itself produce spore to complete the cycle. Colonies of gametophytes can apparently continue to produce ferns for some time, so in cultivation plantlets can be removed and the colony left to continue to reproduce, which is a pretty good deal.

With my little A. peruvianums, the first part of the cycle is complete (although perhaps it’s difficult to call a part of any cycle the first part). What remains to be seen is whether germination can be achieved: the outermost layer of the garden material does not have the constant film of water that the habitat of A. peruvianum does, but I am attempting to keep the area as moist as possible in an effort to assist germination. Here’s hoping for a favourable outcome; the little gametophytes certainly do add an interesting element to the garden, though, at any rate.

Immature Monstera dubia. Image © Anna Haigh; retrieved from CATE Araceae
Immature Monstera dubia. Image © Anna Haigh; retrieved from CATE Araceae
Philodendron hederaceum and P. 'Brazil',growing as nature intended. Image © In Situ Plants.
Philodendron hederaceum and P. 'Brazil',growing as nature intended. Image © In Situ Plants.

We love plants for who they are. We like to see them grow as they have evolved to do, and vertical gardens provide a perfect medium for many plants to do so. The epiphytes (those plants that grow upon trees and other plants) and hemi-epiphytes (those that start life on the ground and then grow up towards the canopy) in particular are very at home in this environment, provided a few basic needs are met.

Without reaching too far into the reasons why many vertical gardening systems are designed to be densely planted from the outset (it seems to have been a natural progression for the industry to provide an instantaneously lush and full garden instead of one which required time to reach its intended glory), we can easily see the effects on the plants themselves. Commonly used plants which typically climb in their natural habitat are perfect examples of this: how often do we see a pothos or Philodendron climbing up a wall instead of cascading down? The weeping effect that the latter creates is admittedly pleasing (though there are plants which naturally possess this type of growth), but I believe that to create a truly spectacular and natural effect the best thing is to allow the plant to grow naturally; that is, up. And to do this, the plant needs space.

Many vertical garden systems are composed of cells, many filled with growing media, and some merely holding potted plants. These systems are fantastic if frequent replacement of plants is necessary, but this type of growing environment does not emulate a natural one. Other systems employ an undivided planting area, where roots are free to grow where they will. In these systems, if a plant is provided sufficient space, it will begin to grow upward, affixing itself to the growing surface with its aerial roots, tendrils, suckers or rhizoids, depending on the species in question. Once growth begins in this fashion it progresses rapidly, and something even more fascinating begins to happen: the plants’ new leaves begin to grow larger than the last! Simply as a result of being able to grow as it has evolved to do, the plant performs better and produces a nicer specimen than one constrained in a planter.

his effect becomes more dramatic still in the case of some hemi-/epiphytic species because they possess a juvenile and adult form. Monstera dubia is a splendid example: the juvenile form of the plant grows with its silver-brushed leaves tightly appressed to the growing surface, but when it reaches maturity it suddenly abandons this growth pattern to produce large green leaves which take full advantage of the higher light in the forest canopy. It uses this extra energy to finally, after its long climb, produce flowers and ultimately reproduce. Incredible!

Many designers of vertical gardening systems seem to have lost their way; in what other horticultural discipline has a garden ever been designed to be instantaneously lush and full (or crowded, for that matter)? Certainly not in most traditional landscaping, and not even in most interior landscaping situations. It is a pity that now many people showing an interest in these gardens are expecting such fullness at the outset, for it is truly at the expense of the true potential of the vertical garden and the species therein.