by
Plant Doctor Chris Satch
You’ve seen them in every insta post, movie background, and even curtain pattern. You may have even tried (or are still) growing one or more of them.
Common houseplants like Pothos, Philodendrons, Alocasias, Monsteras, ZZ plants, Aglaonemas, Arrowhead vines, Colocasias, and others are aroids. In fact, most leafy houseplants are likely to be aroids, so it’s important that you know a little bit about this family and why they actually are easy to grow. Here, I’ll tell you the history of these plants, and give you pointers for general care – Plant Doctor Style! Buckle up, because it’s gonna be a fun ride!
Plant History and Evolution
All aroids are related, and in the plant family, Araceae, which is one of the oldest more primitive basal families of all monocotyledonous plants. This family is made up of herbaceous perennial plants, often with milky, or clear acrid sap. The stems can be vining, tuberous (forming dormant potato-like structures underground to survive unfavorable conditions), rhizomatous (creeping underground stems) or reduced (little to no stem). The leaves contain crystal raphides, with calcium oxalate crystals, which are irritating to herbivores, as they form needle-like fibers, similar to asbestos. The flowers are borne on a spadix, an inflorescence that contains a spathe, usually enshrouding the flower spike, which is often fleshy. Peace lily flowers and Anthurium flowers are a common example of the spadix-type inflorescence, and ones you’ve probably seen.
Araceae, according to fossil and genetic evidence, diverged from the rest of the flowering plants about 115MYA[1] [2]. Of course, it’s hard to give a specific date because evolution happens over time. In fact, it is currently believed that the ancestor to Araceae was a widely distributed plant across all of Pangaea. When Pangaea broke up, only then did the different climates force the Araceae ancestors to diverge and adapt to their new environments.[3] The split happened in three phases[4] – ~175MYA during the Jurassic, 150-140MYA in the Cretaceous, and 60MYA in the Cenozoic (To put that last one into perspective, North America and Greenland broke off of Eurasia AFTER the dinosaurs died!).
While the family did diversify into new habitats, many of its features stayed the same. The ancestors to all Araceae are believed to be either aquatic or swampy plants, which explains their resilience in water, and successful water propagation. The waxy leaves and thick waxy roots on many are adaptations that resist too much water from going inside the plant at any time. They all have retained the spathe-type flower as well.
Interesting Aroids
Skunk Cabbage
Some aroids have the ability to generate heat, like the North American skunk cabbage (Symplocarpus foetidus). It is one of the very few plants to actually generate heat by using stored starches in its roots. Heat generated from the spathe of the flower melts snow, making it one of the first flowers to show up in spring in North America. As the name suggests, this plant stinks, but for good reason. The smell attracts flies and gnats that are active in late February to early March to pollinate it.
Because its leaves are out before any other plant, and given the reflective nature of snow, this plant collects a lot of solar energy. Additionally, the leaves stay on the plant all season, and even though the plant is shaded by trees later in the season, the plant has already reached its peak growth and will continue to collect ambient light to increase its starch storage for the following year.
Monstera
Monsteras are famous for their natural leaf holes, hence the nickname “Swiss Cheese Plant”. The technical term for plants making holes or clear parts in their leaves is called “leaf fenestration”, and is not unique to monsteras. Plants such as Haworthias and Lithops have developed leaf fenestrations for other reasons—their leaf tips are transparent to allow light down inside the plants when they are buried by the frequent sand and dust storms of their native South Africa.
There has been debate and speculation as to how and why monsteras make leaf holes. Some have suggested that Monsteras create holes in their leaves to resist the strong winds of hurricanes. The Bird of Paradise plant (Strelitzia reginae) does indeed split its leaves to allow wind through, but it’s often more exposed in nature than monsteras are. Monsteras cling to a substrate and are often understory plants. Additionally, monsteras can recover pretty well after any kind of reckoning, so that’s not likely the main reason. Others suggest that they have the holes that better allow water to come in contact with their roots. This may be plausible during the dry seasons of some of the areas its native to, as the rain showers are too light in the dry season to fully penetrate the canopy and reach the roots. However, the leaves are often with long petioles that are projected away from the roots, and the aerial roots are often projected in many directions, making this claim dubious.
You might say the ‘hole theories’ have holes in them—there is not enough evidence to support an entire adaptation. The most likely reason why monsteras have holes in their leaves comes to us from Christopher Muir at Indiana University who suggests that it is because of lighting conditions that monsteras have developed holes. monsteras grow from the forest floor in a semi-epiphytic way, vining up trees and such to acquire more light. As it is in such forests, the only way that understory plants can survive is by capturing sun flecks, or small beams of sunlight that make it through the canopy. By modifying the leaf structure to have holes, the same area of leaf can cover a greater area. So, even though a few sun flecks may go through the holes and be missed, the probability/incidence of catching a sun fleck increases because there is more area covered. Additionally, the higher leaves with holes allow lower leaves to catch any missed light below, reducing the need to toss off older leaves – a waste for the plant.
Given good lighting conditions, a whole leaf and a fenestrated leaf will perform the same. It is under scattered light sunflecks/understory conditions that the fenestrated leaf does pick up more sunlight than a whole leaf. However, this is only advantageous if the plant’s growth rate demands it. Because more mature monsteras grow more quickly, it becomes advantageous to utilize all the sunflecks as efficiently as possible.
General Indoor Aroid Care
A special note about Light
In the wild, aroids often grow on the forest floor and have adapted to surviving in many conditions, including low light. In the horticulture industry, we market these plants as “low light” plants, but the truth is, is that no plant really likes to be in low light. Most aroids prefer dappled sunlight. In their native environment, they are understory plants and are shaded, but the sun is not completely obscured.
So again, I REPEAT, DO NOT PUT THESE PLANTS IN LOW LIGHT. No plant likes to be in low light. Failsafe is to put any plant in a window.
Give these plants a tickle of sun, increasing the level of direct sun with the size of the plant. The bigger the plant, the more light it will need.
Water
Allow potting mix to dry out before watering. Soil about 1-2” down should be dry to touch. Water more frequently during warmer months and fertilize during growth season. Generally, the plant will droop to show that it needs more water.
Humidity
Contrary to popular belief, aroids (except Alocasia and “thin-skinned” aroids) do NOT CARE about humidity.
Temperature
65°F-85°F (18°C-30°C). It’s best not to let it go below 60°F (15°C).
Propagation
When propagating, be aware that water is devoid of nutrients. Just because you can propagate in water, doesn’t mean you should keep it in water forever. The plant will not grow as well as if you planted it in soil.
Common Problems
Most aroids are prone to mites, but occasionally scale and mealybugs attack them as well. Treat the plants according to my pest guide here.
SYMPTOM: Leaves EVENLY turning brown and crispy at leaf edges
CAUSE: Under watered, high salts, or potassium deficiency
SYMPTOM: Yellow Leaves
CAUSE: Could be a lot of things! Anyone who tells you that yellow leaves automatically means overwatering has no idea what they are talking about. Yellow leaves is just a distress call. Combined with another factor, and the diagnosis becomes clear.
- Yellowing + leaf curl OR drooping + dry soil = underwatered
- Yellowing + moist soil = overwatered
- Yellowing + moist soil + drooping = too hot
- Yellowing in blotchy way = plant is cold OR staying too wet between watering
- Yellowing + browning of old leaves + stunted growth = needs fertilizer
- Yellowing + blackened stems = root rot; overwatering
- Yellowing of lower/older leaves alone = just old leaves
Other Notes
Irritating to cats, dogs, and humans if consumed, but probably not lethal. Best practice is always to keep houseplants out of reach of small children and pets. Aroids are not particularly hard to grow, and are tolerant of many conditions. Just be mindful of the environment in which you place them, and be aware of the seasons, indoors and outdoors.
[1] Sender, L.M., Doyle, J.A., Upchurch, J.R. Jr., Villanueva-Amadoz, U. and Diez J.B. 2019. Leaf and inflorescence evidence for near-basal Araceae and an unexpected diversity of other monocots from the late Early Cretaceous of Spain. Journal of Systematic Palaeontology, vol. 17, p. 1093–1126.
[2] Nauheimer, L., Metzler, D. and Renner, S.S. 2012. Global history of the ancient monocot family Araceae inferred with models accounting for past continental positions and previous ranges based on fossils. New Phytologist, vol. 195, p. 938-950.
[3] Nauheimer, L., Metzler, D., & Renner, S. S. (2012). Global history of the ancient monocot family Araceae inferred with models accounting for past continental positions and previous ranges based on fossils. New Phytologist, 195(4), 938-950. https://doi.org/10.1111/j.1469-8137.2012.04220.x
[4] Merali, Zeeya and Skinner, Brian J. (2009) Visualizing Earth Science, Wiley, ISBN 047174705X