Calathea Care

Background Information

Calathea is a genus of neotropical rhizomatous herbaceous perennial plants which includes Calathea, Maranta, Stromanthe, Ctenanthe, and more; but are referred to generally as ‘calatheas’ or ‘prayer plants.’  They all hail from the same family, Marantaceae, the prayer plant family.

Simply put, Marantaceae is nicknamed the ‘Prayer Plant’ family due to the daily movements of the plants leaves, known as nastic movements. Various plants in this family move their leaves up at nighttime, and lower them in the daytime in accordance to a circadian rhythm (nyctinasty). They move their leaves by changing the water pressure in their pulvini, the swollen nodes at the base of the leaf, along the leaf stalk (petiole). It is believed that these movements are meant to follow the sun’s movement in the sky in order to maximize light absorption on the forest floor.

Like members of Oxalidaceae and Fabaceae, these plants have enlarged pulvini (singular – pulvinus), which are fattened joint-like structures on the leaf petioles. When the leaves are to be raised, the cells within these structures swell with water, due to signaling from phytochromes in their cells.  Phytochromes are the protein receptors for light, and are how plants see light.

There are two major phytochromes involved in how a plant senses when it is day or night – Pr and Pfr.  Each is named after the wavelength of light which converts it to the other form.   Pfr is created from Pr, when the plant receives near-red light from the sun (during the daytime). Pfr is the active form of the protein, whereas Pr is the inactive form.  When created, Pfr activates other signals and genes in the plant that allow it to do daytime activities.  Pr is created when the plant receives residual far-red light, which occurs at dusk.  In darkness, Pfr naturally reverts to the inactive Pr.  In short, it is through the Pr/Pfr cycles that the plant is able to tell when it is daytime.

Figure 1

These rhizomatous perennial herbs are native to moist or swampy tropical forests, particularly in the Americas but also in Africa and Australasia. Members of the family vary from plants with slender, reedlike stalks to leafy spreading herbs to dense bushes nearly 2 m (about 6 feet) high. They have rhizomes, which are usually white, and some species are ethnobotanically important. The most well-known species in the family is arrowroot, Maranta arundinacea, native to the Caribbean, is grown in parts of the Caribbean, Australasia, and sub-Saharan Africa for its easily digestible starch. Various species of Calathea, Maranta, and Stromanthe are grown for their ornamental foliage.

This family has members both in the neotropics as well as the African and Australasian tropics, which genetic evidence suggests are not too distantly related.  It is likely that, while the continents were joined as Pangaea, this family was widespread across Gondwanaland (the single landmass of S. America, Africa, Antarctica, Australia). After the continents split into their current landmasses, there was an isolation of the neotropical species. Some phylogenetic analyses place Calathea and Maranta as polyphyletic – meaning that some neotropical species are more closely-related to the African species than they are to each other.  This not only supports the existence of Pangaea, but also suggests that the family was already well-evolved before the continents split.  It is common for members of plant families to be distributed across Africa and South/Central America.

Calathea leaves are used in the tropics (mostly Brazil) for handicraft and food wrapping. The waxy leaves of Calathea lutea make it perfect for food wrapping.  Longer leaves of other prayer plants are used in basket weaving by indigenous peoples.  The colorful leaf markings of most Calatheas make them economically important as houseplants, and their popularity has been growing. The Calathea veitchiana ‘Medallion’ (Medallion calathea), Calathea lancifolia (Rattlesnake calathea), and the Calathea ornata (Pinstripe calathea), are some of the most popular species.

General Care

Light

Bright ambient light with a few hours of direct sunbeam exposure.  A dappling (or tickle) of direct sunbeams all day is fine too.

Water

Watering frequency depends on light levels provided. Allow soil to half-dry out before watering. Soil should be almost dry about 2” down before watering again.  They don’t mind drying out completely between waterings, but can’t stay dry for long.

Humidity

Does better in higher humidity if possible, but otherwise can tolerate lower humidity if the soil stays moist.

Temperature

65°F-85°F (18°C-30°C). It’s best not to let it go below 60°F (15°C).

Common Problems

Prone to foliar fungal infections. Keep leaves dry. May get spider mites and mealybugs. Treat spider mites and mealybugs as soon as they appear with weekly sprays of hort oil or insecticidal soap.

SYMPTOM: Crisping curling or burnt leaf tips or edges.
CAUSE: Foliar fungus.  Spray with copper fungicide.

SYMPTOM: Wilting and curling leaves coupled with dry potting mix.
CAUSE: Underwatered, thirsty plant

SYMPTOM: Yellowing, possible black stems, mushiness, falling apart/collapsing.
CAUSE: Roots rotting; overwatering

Other Notes

This plant is pet-friendly, but the best practice is always to keep houseplants out of reach of small children and pets. Honestly, these are super prone to foliar infections, and will keep the foliar infections at bay if given more light, and not spritzed.

Citations:

Tripathi, S.; Hoang, Q.T.N.; Han, Y.-J.; Kim, J.-I. Regulation of Photomorphogenic Development by Plant Phytochromes. Int. J. Mol. Sci. 201920, 6165. https://doi.org/10.3390/ijms20246165 and https://www.mdpi.com/1422-0067/20/24/6165

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