March 4, 2024

Water, light and temperature are three of the limiting factors that we find in the cultivation of plants. And, in addition, they make their anatomy adapt to these conditions. Observing what the leaves and stems of the different species are like can give us a clue about the care they need to survive. If we also pay attention to the climate of origin, we will add one more resource to cultivate them better.

If we were a plant and had to survive on just 25 millimeters of annual rainfall and a scorching sun, our anatomy would have to reflect the harshness of that habitat. It is in this situation that an exceptional species, Welwitschia mirabilis, is forced to vegetate in the Namibian desert. Thus, in this circumstance, its body has been reduced to two rigid leaves that start from a woody growth base and hardened like a stone. In another similar environment, also linked to very little rainfall, we could also have choose develop a taller size, and create a giant green column to store water and nutrients with which to face long periods of drought. This anatomical adaptation would be found, for example, in the saguaro (giant carnegiea). In order to also avoid excessive evaporation that occurs when the sun is present, the metabolism of this and other cacti causes the plant to remain sealed during the day. Consequently, the saguaro will only open its stomata —the organs responsible for carrying out gas exchange with the atmosphere— during the night, something that also does welwitschia.

This drought may be seasonal, linked mainly to the summer months. So, as do many bulbous plants like tulips (tulip spp.) or daffodils (narcissus spp.), for part of the year they will not be visible growing on the ground, but rather buried under it, encapsulated in conspicuous reserve organs called bulbs. When the rains return, they will sprout again from those underground buds.

A tulip in full bloom.
A tulip in full bloom.Edward Beard (Eduardo Beard)

On the contrary, if we lived in an environment with an abundance of water throughout the year and with milder and more stable temperatures, we could be prodigal by filling ourselves with leaves and stems. Those huge trees in the Amazon, or those climbing plants in the jungles, should not save resources. One only has to look at the huge blades of Adam’s rib (delicious monstera) to understand that finding water is not a problem for her, and that she has it in abundance. So that its great leaves do not function as a roof and displace water away from the roots of the plant itself, they have been filled with holes so that when it rains the drops can wet the base of the plant and its aerial roots.

And what would happen if the light that arrives is not too much? Then we would become very efficient at capturing even the smallest beam of light that penetrates to the ground. This is what happens to the understory plants, which live at the foot of the trees, such as the well-known aspidistra (Aspidistra elatior). The pilistra, which is another of its common names, is native to the Ōsumi Islands in Japan, where it grows under large evergreen shii trees (Castanopsis sieboldii). Thanks to their adaptation to their natural habitat, aspidistras like indoors, and their broad, very dark green leaves and their leathery consistency can give us two clues about their cultivation: they resist shade and also drought.

Many glaucous plants indicate their fondness for direct sun.
Many glaucous plants indicate their fondness for direct sun.Edward Beard (Eduardo Beard)

On the other hand, if the solar radiation is so abundant that we need to do something to alleviate this excess of light, we can opt for what many Mediterranean aromatics do, which reduce the surface of the leaf to the extreme. This is the case of rosemary (Salvia rosmarinus) or lavender (Lavandula angustifolia). In both, its leaves are very narrow, lanceolate, and show whitish colors. These glaucous tones are found in rosemary on the underside of the leaves, with a tangle of fine hairs that protect the stomata and thus prevent excessive water loss. In lavender, it is the entire plant that shows that glaucous color, thanks to its hairy surface, which reflects part of the excess of the sun, as a house painted white would.

With this brief and incomplete review of the anatomy of some plants, we remind you of how essential it is to pay attention to both the morphology of their bodies and the place of origin of the plants we grow. Not infrequently we see rosemary that are planted in the shade, contravening its perfect adaptation to the sun, and that is when we see them grow sad and light green in color and without flowers. Or we find aspidistras planted under the midday sun, with their burned, yellowish leaves, exhausted by so much solar radiation.

Saguaros and other species adapted to the lack of water and high temperatures at the Desert Botanical Garden, in Phoenix, Arizona, in November 2021.
Saguaros and other species adapted to the lack of water and high temperatures at the Desert Botanical Garden, in Phoenix, Arizona, in November 2021.M.Porcel

Therefore, if we take into account the shapes of its leaves and stems, its consistency, its colors and its growth habit, on many occasions we can learn to cultivate them correctly. There are no general rules, because in the plant world there will always be exceptions to the rule, but we will enjoy sharpening our gardening intuition. And, by the way, if we investigate the place where our companions come from and are attentive to the climate to which they are adapted, it will make us more successful when we take care of them here, by our side. Along the way it will be like traveling, illustrating our days with the echo of distant lands.

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