Between Leaves and Shapes: A Journey to the Universe of Araceae

By Inhotim

Anthurium. Calla lily. Yautia. Taro. Swiss cheese plant. These species are part of the daily lives of many people. Scientifically speaking, they belong to the same family, known as arum or Araceae, and also colloquially as aroids. In addition to these five species, there are many other types of them. More than 3,000 species have already been described, and each year new ones are revealed. The Araceae family is exceptionally diverse, encompassing shrubs, climbing plants, epiphytes, and even aquatic plants. They are essential to the composition of tropical gardens. Landscape designer Roberto Burle Marx had a noteworthy interest in the arum, especially for their diversity of shape. His interest in this group first appeared as a child and followed him throughout his entire life. At Inhotim, landscape designer Pedro Nehring takes advantage of their variety of shapes, colors, and textures to compose the gardens, harmonically combining native and exotic plants. The Araceae are so important in the landscape vocabulary of Inhotim that they ended up becoming the second most representative family of the botanic collection. “Talks on Anthuriums, Philodendrons, and Other Araceae” is a perspective of the diversity of Araceae in the Institute, followed by fascinating stories of popular knowledge.

Xanthosoma sagittifoliumInhotim

Shapes

Generally, aroids are recognized by their arrow-shaped leaves of green color, lustrous and resistant. However, many of them have leaves in other shapes, sizes, and color variations. There are species whose leaves can surpass two meters of length. As for their format, there is a wide variety within this group. Leaves can be arrow-shaped (sagittate), heart-shaped (cordiform), spear-shaped (lanceolate), with flat, cut, undulated, or sinuous leaves, in addition to many other interesting details that make the difference for people curious about or already initiated in the art of gardening. Such impressive diversity and adaptability to indoor environments explain the increasing amount of people interested in cultivating this family at home, becoming true arum collectors!

This aroid is known as one of the biggest Philodendron species in the world. Its leaves are huge, bright, vigorous, and so thick to the touch that they recall the texture of leather. As this plant lives under gigantic trees in the Amazon, the size of the leaves is important due to the increased ability to capture sunlight. The thickness, on its turn, contributes for such a big leaf not to crack. Notice that the features of the leaves often indicate the natural environment where the species live.

Philodendron maximumInhotim

Philodendron mayoiInhotim

Cyrtosperma johnstoniiInhotim

In addition to its undeniable aesthetic qualities, the rhizome (subterranean stalk) of this plant has been used in traditional Thai medicine for treating many conditions, including several types of cancer. A 2013 study showed that extracts of it bear antioxidant and anticancer compounds, for it effectively inhibits cancerous cells without affecting normal cells.

(detail)Inhotim

Anthurium sp.Inhotim

(detail)Inhotim

Philodendron melanochrysumInhotim

Colors and textures

From bright green to vinaceous-purple, the colors of the aroids bring life to external gardens, apartments, and floral arrangements. More than that, the colors and textures often indicate the appropriate place to grow them. In the vegetal world, shades of red and purple might be related to the production of anthocyanin, a pigment that protects the plant from sun rays. Red and purple leaves often have a more intense coloration when exposed to the sun, since these pigments act as some sort of sunscreen. On their turn, variegated leaves, those with spots of colors other than green, manifest due to the absence of chlorophyll or by the predominance of other pigments, such as the previously mentioned anthocyanin. The variegation can appear naturally as a mutation of the plants, a feature frequently preserved by ornamental growers in search of unique aesthetic effects. However, unpigmented plants do not tolerate low brightness and are sensitive to sunlight exposure.

The leaves of the black velvet stand out for their white veins appearing on top of the metallic green darkened color. It is one of the few almost black plants in nature. It doesn’t tolerate low temperatures and must be cultivated under good lighting, yet without direct sun exposure. It must be watered deeply but very seldomly, so that the substrate where it is being grown can always have enough time to get dry from one watering to the next.

Alocasia reginulaInhotim

The colors of the heart of Jesus turned this species into a famous one whether for cultivating in pots or gardens, and it is currently available in the market in a wide variety of shades – pink, white, green, and red. During winter, it loses its leaves, emitting new sprouts in spring. It has been scientifically proved that the extract of its leaves has anticonvulsant, anxiolytic, and antidepressive properties. However, it is extremely toxic, and must be kept away from children and pets.

Caladium bicolorInhotim

Taro has big leaves with colors ranging from green to dark purple, almost black. The dimension, color, and brightness of the leaves give an interesting decorative aspect, which makes it popular as an ornamental plant. In addition to the ornamental foliage, taro is also widely cultivated for feeding purposes. Along with potato, manioc, and sweet potato, taro is part of the amylaceous group, consumed by 70% of the world population and rich in carbs, mineral salts, and vitamins B and C.

Colocasia esculentaInhotim

(detail)Inhotim

Anthurium salviniiInhotim

Flowers and fruits

The aroids are usually known for their ornamental foliage, but many of these species have striking flowerings! As in the picture, the inflorescence (set of flowers) typical to an aroid has a thick, fleshy axis sustaining minuscule flowers, protected by a modified leaf, the spathe, that can also attract pollinators. When there is pollination, these flowers go through an extraordinary transformation and turn into succulent fruits. When the seeds are fully formed, steeped in mucilaginous pulp, the plant announces a new need: it is the time of dispersal agents. Most animals are attracted by bright colors, and many Araceae respond to this fact by changing the color of their unripe fruits to red, orange, yellow, or purple. The succulence and the sweet flavor of fruits are also a strategy to increase the chances of consumption by the fauna.

Since its discovery in nature, the colorful spathe of the miniature tailflower is one of its major eye-catchers. Several hybrids have been produced in order to obtain a variety of spathe colors. The colors originate from variations in the production of chlorophyll, as well as in the type and levels of anthocyanin. The white coloring represents pigment loss. Either way, this plant is an excellent option to be used in inside spaces, because it is easy to take care of and produces lasting flowerings of lively colors.

Anthurium amnicolaInhotim

Although the Philodendron genus has a broad variety of leaves shapes and can occupy several types of environments, the inflorescence aspect is pretty much conserved. In this genus, the spadix is surrounded by the spathe almost throughout its whole extension, as we can observe in the inflorescence of the ‘waterfall’ Philodendron. Several members of the genus also have highly thermogenic flowerings, that is, the flowers produce heat so as to attract pollinators. This feature is very common amid the Araceae.

Philodendron ‘Cascata’Inhotim

Typhonodorum lindleyanumInhotim

When fully-developed, the fruits of this aquatic species are small yellow berries with one single seed. In Madagascar, they are used to feed humans and animals after being toasted or cooked. The vegetative parts of the plant are also used, mostly in the construction and manufacturing of implements and tools. It must be cultivated in full exposure to the sun in permanently wet ground (approximately one meter deep), fertile and rich in organic matter.

(detail)Inhotim

Inhotim

It is said to be the favorite fruit of Isabel, Princess Imperial of Brazil, and it tastes like a mix of pineapple and banana. Yet, be careful: unripe fruits might contain high concentration of calcium oxalate, which causes throat irritation. Due to its remarkable features, it is currently a naturalized plant in the entire tropical world.

(detail)Inhotim

Philodendron sp.Inhotim

Habits and habitat

Despite the fact of being predominantly climbers, the Araceae can also take the form of herbs and bushes. In this group, there are examples of geophyte (tuberous and subterranean stem), epiphyte (on other plants), rupicolous (on rocks), and helophyte (plants growing in soaking or flooded grounds). This way, the aroids occupy a variety of environments and develop appropriate structures in each of them to allow for their survival. The roots, for instance, can be subterranean, aerial, or aquatic, and each of them has different features and functions, such as fixing in soil, keeping in support, or absorbing nutrients. The main threat to the Araceae is the loss and reduction of quality in their natural habitats. Some species are highly adapted to specific environments and cannot survive under altered conditions. The removal of tropical forests eliminated most of terrestrial, climber, and epiphyte species, since many of them require a shaded environment.

Pistia stratiotesInhotim

Philodendron erubescensInhotim

Just as it happens to most aroids, the brushing philodendron’s knots, which are the regions of the stalk from where leaves sprout, produce aerial roots, known by this name because they remain exposed outdoors instead of being subterranean. These roots take the role of fixing the plant to a tree trunk, i.e., the roots are specialized in sustaining this ‘alpinist’ plant. It also stands out for its shades of red, and to such an extent that the term erubescens in its name means something or someone who blushes.

(detail)Inhotim

In 2018, botanists recognized that these plants were genetically different from the philodendrons with which they were previously grouped. Along with the fact that they grow similar trunks to those of trees and lose their lower leaves, leaving the stalk covered in scars. The plants have then been transferred to their own taxon: Thaumatophyllum. When grown domestically, most plants of this genus remain quite compact, except if they are very old.

Thaumatophyllum bipinnatifidumInhotim

Credits: Story

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Audios: Prof. Dr. Claudia Fabrino Machado Mattiuz - Professor at the Luiz de Queiroz School of Agriculture (ESALQ), University of São Paulo (USP) - Department of Plant Production
João Eduardo dos Santos - Nurseryman and botanical identifier
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