Plants With Weird Foliage: Window Plants

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Frithia pulchra, sometimes called baby toes, is one of many curious window plants. Source: venanaturale

Here is another article about plants with truly startling and unusual foliage, a short series I intend to add to from time to time. This article therefore follows Five Plants With Weird Foliage, Four Other Plants With Weird Foliage and Plants With Weird Foliage: Perfoliation. Just click on the links if you ever want to re-read them.

How Leaves Function… Normally!

Although there are nearly 400,000 species of plants on our planet, most have leaves with exactly the same structure. First, there is a dark green upper surface. Its color comes from chloroplasts, the green cells that convert sunlight into energy and are located just below the leaf’s upper surface. The underside of the leaf, though, has few chloroplasts and is therefore a paler green. This organization is very logical, because the plant’s goal is to capture a maximum of solar energy and the sun is located above the plant, not below. Even the way most leaves are held on the plant, that is, horizontally, is designed so they can absorb all the solar energy possible.

When the Sun Is Too Intense

So much for a typical leaf! But some plants, especially those of arid climate plants, face a rather unusual situation. The sun where they grow is so intense it can burn the leaves. Also, they can’t possibly absorb all the energy it produces. Most plants living under arid conditions have had to find some way of protecting themselves from the sun’s excesses.


Many plants that grow in the extreme sun of arid climates, like this panda plant (Kalanchoe tomentosa), have leaves covered with protective hair or wax: Mother Nature’s sunscreen. Source:

These plants have different strategies to get around an overly intense sun. Sometimes the leaves are covered with wax or hair that reflects rather than absorbs light, sometimes the plant sacrifices its leaves entirely and photosynthesizes through its green stems (cacti are good examples of this) and sometimes the plant gives up entirely, losing its leaves and retreating into dormancy, often underground, during the hot season. But of all the adaptations to an overbearing sun, window plants have come up with the most fascinating adaptation.

Nature’s Skylight

20180119C Eng C.T. Johansson, Wikimedia Commons &

Most window plants, like this Lithops, grow nearly buried, with only the leaf tip showing. Sunlight penetrates the window and can easily reach the chloroplasts located all round the inside surface of the leaf. C.T. Johansson, Wikimedia Commons &

Most window plants pull themselves down into the ground during the summer, leaving only the tip of their leaves exposed. And this exposed part is not green, although it may look that way at first, but rather translucent, like a window. Thus, the intense and burning light penetrates through the tip of the leaf, but is then diffused by the gelatinous translucent sap inside and redirected to the chloroplasts which are located inside the leaf, near the outer walls, and therefore literally underground. It’s all rather like a skylight. The transparent leaf tip of window plants is rarely sharply pointed, as that could lead to water loss. It is rather truncated or rounded, as that reduces the surface exposed to drying winds.

This ingenious adaptation, which botanists call a leaf window, an epidermal window or fenestration, has evolved not once, but several times in different families. The best-known window plants are the living stones of the Aizoaceae family, a group which, broadly viewed, can be said to include Lithops, Fenestraria, Frithia, Ophthalmophyllum, Conophytum and several other genera. However, there are window plants in other families, including the Asphodelaceae, Asteraceae and Piperaceae families.

Curiously, the vast majority of window plants come from the same region: the deserts of southern Africa. What is not clear, though, is why. What is so special about the conditions in this region that stimulates plants to develop—independently!—a window rather than or in addition to other methods of surviving drought used by plants in other desert climates, such as succulence, summer dormancy, reduction of stomata and others? I’m sure someday botanists will find an explanation.

The Mother of All Window Plants

20180119D Fenestraria rhopalophylla, Stan Shebs, WC.jpg

Fenestraria rhopalophylla: the windows look like contact lenses!  Stan Shebs, W

The most windowlike of the window plants is undoubtedly Fenestraria rhopalophylla, in the Aizoaceae family. In fact, it is often simply called “window plant” in English (baby toes is the other common name) … and that’s also the meaning of its botanical name Fenestraria. This plant forms a rosette of upright pale gray-green tubular leaves, each capped with a rounded and completely translucent tip: it looks like it was wearing a contact lens!

In nature, only the translucent tip is visible, the rest of the plant remaining buried. When grown as a houseplant, we like to expose more of the leaf, partly to highlight the plant’s curious form, but mostly because it’s hard to imitate the intense drought and dry heat of its native country in our homes: if we bury the leaves the way they grow in the wild and the soil around them remains the slightest bit moist, the poor plant tends to rot.


20180119Z Frithia pulchra C. T. Johansson, WC .JPG

The other baby toes, Frithia pulchra, has leaves more truncated than rounded. Source: C. T. Johansson, Wikipedia Commons

Frithia pulchra, also in the Aizoaceae, is very similar, with the same tubular leaves and rosette growth, but this time the ends appear truncated rather than rounded. And the flowers are pink rather than white or yellow (the case with Fenestraria). This plant too is commonly called window plant or baby toes.


20180119E Lithops, Rudolf Marloth, WC.jpg

Living stones grow nearly buried in the soil. The upper surface of the leaf is marbled with a mix of translucent and opaque patches, making it look like a stone or rock. Colors vary widely, according to that of the surrounding rocks. Source: Rudolf Marloth, Wikimedia Commons

The plants most often referred to as living stones are in the genus Lithops (Aizoaceae) and all have windows, but they are not as apparent as those of Fenestraria or Frithia because the window is marbled with paler opaque patches that mimic the coloration of the neighboring rocks.

20180119R Lithops

Lithops come in a wide range of colours. The darker patches are translucent windows, the paler ones, opaque tissues serving as camouflage. Source:

Each living stone (and there are dozens of species) consists of two succulent half-moon leaves pressed against each other, plus a few roots. The leaves can be green, gray or even reddish.

Among other living stone genera that include species with windows are Conophytum and Ophthalmophyllum.

Mini Aloes

The genus Haworthia is closely related to the better-known genus to Aloe (both belong to the Asphodelaceae family) and indeed, most species look much like small aloes, with succulent leaves, a rosette growth habit and sharply pointed leaves.

20180119F Haworthia cymbiformis obtusa 賴永聰 , pinterest.jpg

Haworthia cymbiformis obtusa has very striking windows.  Source: 賴永聰, pinterest.

Species with windows, such H. cymbiformis and H. retusa, sometimes called cathedral window haworthias, are different. They have leaves with a more rounded, translucent tip and in nature, live essentially underground with only that part of the leaf exposed.

20180119N Haworthia truncata, Stan Shebs, WC.jpg

Haworthia truncata: the flat upper surface of the leaf is a window. Source: Stan Shebs, Wikimedia Commons

The most extreme window haworthia is H. truncata, sometimes called horse’s teeth. The end of each leaf is “truncate,” as per the species epithet truncata, meaning it looks like it has been cut off … with a saw. The leaf tip appears dark green, but is, in fact, translucent. This species usually grows in a fan shape rather than the more typical rosette common to haworthias. It’s a distinctly odd-looking plant!

20180119G Bulbine haworthioides Jeffs-bulbesetpots,

Most unusual and rarely grown, Bulbine haworthioides bares ground-hugging leaves with numerous translucent windows. Source: Jeffs-bulbesetpots,

Another genus of the family Asphodelaceae, Bulbine, also produces a few window plants (notably B. haworthioides and B. mesembryanthemoides). Their succulent leaves form an entirely flattened, ground-hugging rosette marked with translucent patches. Curiously, many other bulbines have fairly ordinary succulent leaves, much like an aloe, and others have deciduous grasslike leaves and underground bulbs or tubers. They spend the dry season safely underground, fully dormant.

Cat’s Eyes

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Only when the leaves are backlit are you likely to notice the narrow windows on Senecio rowleyanus. Source: Green Lady, YouTube

String of pearls or rosary plant (Senecio rowleyanus), a popular houseplant in the Asteraceae (sunflower) family, is also a window plant, but its window is rather discreet. Its small leaves, almost as round as a pearl with just a small pointed tip, are medium green … but this is not the part of the leaf that carries out photosynthesis. If you look closely, you’ll see that each leaf has what looks like a darker green ray like a cat’s eye, but which is, in fact, transparent. It’s through this slit that the light penetrates the leaf and reaches the photosynthetic cells on its inner periphery.

This window often goes unnoticed and many people grow this fairly common succulent without realizing how truly extraordinary it is. The window is best noticed when the plant is backlit by sunlight and it then appears yellowish green and distinctly more translucent.

Unlike other window plants seen so far, string of pearls does not grow half-buried, but usually completely exposed. The rounded leaves are borne on long, thin, creeping or trailing stems and it grows as a groundcover in the wilds of southern Africa, its stems rooting where they touch soil. As a houseplant, it’s most often grown in hanging baskets as a trailing plant.

20180119I Senecio radicans

You can barely make out the window on the banana-like leaves of  Senecio radicans. Source:

The chain of bananas (S. radicans) is similar in habit, but, as the name suggests, its more elongated leaves look somewhat like bananas. String of beads (S. herreianus) fits in between the two. Its succulent leaves are somewhat rounded, yet more pointed than S. rowleyanus. Both have the same kind of very narrow slit-like window.

A Leaf in Prayer

The window plants we’ve seen so far all evolved independently in southern Africa, but there is one major exception.

In the vast genus Peperomia of the family Piperaceae, with over 1500 species distributed throughout the tropics, there is a handful of species of window plants, all from Peru and Ecuador. The logic behind their fenestration is not so clear as with the African succulents, because these peperomias don’t live in a desert environment, but rather in tropical forests, often as epiphytes. But they are succulents, with thick leaves that store water, something that can be useful to an epiphytic plant, given it has no soil to protect its roots from dehydration and is constantly exposed to drying winds.

20180119J Peperomia dolabriformis

The leaves of the prayer peperomia (Peperomia dolabriformis) seem to be folded in half. The dark green streak on top of each one is the window. Source:

What is fascinating with the best known of these window plants, the prayer peperomia (P. dolabriformis, whose specific name means “shaped like a doloire”, a kind of axe) is that it seems to have been caught midway through its evolution, as if it weren’t quite finished. Just looking at the strange leaf, you can easily see that what was originally an ordinary elliptical and flat leaf has folded upward and inward, like a praying hand (the origin of the common name prayer peperomia) as if to protect its upper surface. What was originally the paler green back of the leaf is now borne upright with a slightly depressed window now separating the two halves. The window looks dark green, but is actually transparent and sunlight can travel through it to the chloroplasts lining the inside of the leaf.

20180119K Peperomia graveolens

Peperomia graveolens. Source:

There are other peperomias with a similar habit. This group includes P. nivalis and the very interesting P. graveolens, where the outside of the leaf is red and thus contrasts strikingly with the green window in the center.

20180119L Peperomia ferreyrae

The narrow leaves of Peperomia ferreyrae don’t display their window too readily, but you can seem them if you look carefully. Source:

P. ferreyrae, with narrow, pointed, scimitar-like succulent leaves, seems to have evolved further than the others, because you no longer notice the effect of a leaf folded in half. Its windows are present, but quite discreet.

20180119M Peperomia columella

Peperomia columella. Source:

Finally, the most bizarre of all the window peperomias is undoubtedly the columnar peperomia (P. columella), a short, upright plant whose small, stubby, very succulent leaves look like they were chopped off at the tip.

The window plants are truly fascinating … and many of them make attractive, easy-to-grow, thought-provoking houseplants. Place a window plant in front of your window today!20180119C Eng C.T. Johansson, Wikimedia Commons &


Plants With Weird Foliage: Perfoliation


Lonicera sempervirens is one of many plants with perfoliate leaves. Source: Stan Shebs, Wikimedia Commons

I’m writing a series of blogs about plants with weird foliage, blogs that will appear occasionally, according to the time I have to write them… and my whims. Two previous articles have already appeared: you can read them at 5 Plants With Weird Foliage and 4 Other Plants With Weird Foliage.

I’m dedicating today’s blog more to a type of foliage than to the plants themselves: perfoliate leaves.

The Conjoined Twins of the Plant World

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Most leaves are petiolate (they have a petiole or leaf stalk). Others lack a petiole and are called sessile. Source: Michael G. Simpson, Wikimedia Commons

Most angiosperm leaves – probably over 95%! – are attached to their stem by a short stalk called a petiole (or leaf stalk). They’re said to be petiolate. Most of the remainder are sessile – they attach directly to the stem, with no petiole – and others yet wrap partly or entirely around the stem and may be said to be clasping or sheath leaves. But the oddest situation of all is when the leaf forms right around the stem, to the point where the stem appears to grow right through the leaf. These leaves are said to perfoliate.

20180108C ENG Michael G. Simpson, WC.jpgThe word perfoliate comes from modern Latin perfoliatus, from Latin per- (through) and foliatus (leaved). It thus literally means “with leaves that are pierced.”


The cup plant (Silphium perfoliatum) has large perfoliate leaves. Source:

Most perfoliate leaves evolved when a pair of opposite leaves gradually fused together. This is the case with the giant perennial, Silphium perfoliatum, called the cup plant, because rainwater often accumulates in the depression where the two leaves join. With this plant, you can still clearly see that there were originally two leaves that joined together, but many perfoliate leaves have so clearly merged that they appear to be one single, often round leaf.

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Bupleurum rotundifolium has single leaves that became perfoliate. Source: Stefan.lefnaer, Wikimedia Commons

Not all perfoliate leaves derive from opposite leaves fusing together. Sometimes a single leaf not only wraps around the stem (it’s said to be clasping or amplexicaul), but its base extends outwards until it takes on the appearance of a single leaf stabbed through the heart by a stem. Thoro wax (Bupleurum rotundifolium), an attractive if rarely grown annual, is in this group.

There and Back Again


Juvenile leaves of spinning gum (Eucalyptus perriniana) are perfoliate, but mature ones are petiolate.

Oddly, many plants go back and forth from perfoliate leaves to more classical petiolate or sessile leaves over their lifetime. Many eucalyptus trees, like spinning gum (Eucalyptus perriniana), have perfoliate juvenile leaves, yet willow-like, opposite, stalked adult leaves. If you prune a mature branch back, new juvenile perfoliate leaves will appear… for a while.

Likewise, many climbing honeysuckles, including Lonicera sempervirens (see the photo at top of this article), produce perfoliate leaves on their flowering stems, but opposite, stalked leaves elsewhere.

It Happens in the Best of Families

Perfoliate leaves evolved separately in different plant families (Apicaceae, Asteraceae, Caprifoliaceae, Colchiaceae, Crassulaceae, Fabaceae, Montiaceae, Myrtaceaeae, Plantaginaceae and many others). I won’t hazard a guess as to why they evolved and there are probably dozens of reasons why a perfoliate leave could be useful in some circumstances and not so much in others.

Perfoliation is still a fairly unusual trait, one botanists certainly notice, which is why you’ll find that many plants with perfoliate leaves have perfoliataperfoliatus or perfoliatum as their specific epithet. It’s often the most obvious distinguishing feature between two otherwise similar species.

Perfoliation in Your Garden


Miner’s lettuce (Claytonia perfoliata). Source:

Among the most widely available temperate-climate plants with perfoliate leaves are miner’s lettuce (Claytonia perfoliata, syn. Montia perfoliata), a quick-and-easy though little-known vegetable, the aforementioned cup plant (Silphium perfoliatum), becoming quite popular as a perennial for the back of the border, and several of the climbing honeysuckles. Common teasel (Dipascus fullonum), often a weed, but sometimes grown as an ornamental, likewise has perfoliate leaves.

In mild climates, several perfoliate eucalypti are widely grown.

20180108G Crassula perforata, www.sedumphotos.net_.jpg

String of buttons (Crassula perforata) is common enough in nurseries in one of its varied forms,

Indoors, or for mild arid climates, string of buttons or necklace vine, Crassula perforata, comes in various forms, from densely stacked and upright to loose and trailing and all have perfoliate leaves. You ought to be able to find at least one type in any garden center. C. rupestris marnieriana is similar, with smaller, fleshier leaves.

20180108H Crassula umbella,

Umbrella crassula (Crassula umbella). Source:

Much rarer and very much weirder is the umbrella crassula (Crassula umbella) with distinctly umbrella-shaped leaves, sometimes wine-red underneath (cultivar ‘Wine Cup’). Extremely odd! Trying growing this one from seed.

Grow crassulas as you would any houseplant succulent: intense light and moderate waterings.

The Button Plant Clan

20180108J Conophytum ernestii

Conophytum ernestii about to burst into bloom. Source:

I’m not sure that conophytums (Conophytum), also called button plants, really qualify as having perfoliate leaves, as there is certainly no leafy stalk that grows through what are really two leaves fused together… but there is a flower, which seems to sprout magically smack dab in the center of what appears to be single buttonlike leaf.

20180108P Conophytum calculus, Abu Shawka, WC.jpg

Some button plants, like this Conophytum calculus, have leaves that are almost perfectly round. Source: Abu Shawka, Wikipedia Common

As the author of this text, I figure I get to choose, and hereby declare conophytums perfoliate for the purpose of this article. And I think conophytums are simply the most fascinating of all the perfoliate plants.

20180108K Conophytum bilobum, MIke Peel,

This conophytum (Conophytum bilobum) isn’t quite so button like, but still has very curious leaves. Source: Mike Peel,

Conophytums are among the many plants called living stones, all natives of southern Africa from the ice plant family, the Aizoaceae. Other living stones are found in such genera as Lithops, Fenestraria, Frithia and Pleiospilos and that’s only a partial list! All are ground-hugging succulents that survive a hostile, arid environment by camouflaging themselves as stones. Not all of the some 100 conophytum species are buttonlike, though. In fact, many bear pairs of cone-shaped leaves, whence the genus name Cono (cone) phytum (leaf). Still, over a third of them are distinctly buttonlike.

Conophytums may be cute as a button, but growing them is not so easy. Read more about them here: Growing Button Plants.

Perfoliate leaves: weird enough to star in science fiction movies, yet common enough to be found in most environments if you look carefully. Keep your eyes peeled!