By Robert Parsons

Robert Parsons, a lifelong plant enthusiast, graduated from the University of Manitoba with a degree in Agriculture in 1991, majoring in plant science and specializing in horticulture. He works as a gardener for a landscape and maintenance firm in Winnipeg. In addition to houseplant culturing, his hobbies include field botany and birding.

The ZZ plant is relatively new to the houseplant trade, dating back to the mid 1990s, when Dutch nurseries began large-scale propagation of the plant and introduced it to the horticultural trade (Horwood, 2007). I grew up as a houseplant aficionado, primarily in the 1970s, and considered myself conversant with most popular cultivars, but this was not one of them at the time. I saw a request by someone for recommendations for robust and easy to grow houseplants and this was one of them by a number of people who responded. I had never even heard of the plant, nor was it in any of my houseplant books, and so I felt the need to learn more. I was struck by its appearance, looking to me like a combination of a palm and a fern. Especially notable were the very shiny green leaves, making them look almost artificial. People looking at them have asked me if they are real plants.

Description
Zamioculcas zamiifolia is the only member of its genus, and is part of the family Araceae, collectively called aroids as a common name. Aroids include many familiar houseplant genera, such as Philodendron, Monstera, Dieffenbachia, Aglaonema and Spathiphyllum. While it is atypical in its growth form compared to most other aroids, the flower, a green spathe with a spadix of creamy white flowers, certainly resembles Dieffenbachia and Aglaonema flowers, showing evidence of their kinship. The name Zamioculcas is derived from the cycad genus Zamia and the elephant ear genus Colocasia, called “culcas” in an ancient Middle Eastern dialect (Flora of North America Online), both of which it resembles in appearance, although only the latter is related to it.

Unlike the majority of aroids, which are noted for their vining or creeping growth form, the ZZ plant’s growth is primarily underground where its thick fleshy roots and rhizomes are. The latter are often tuber-like in appearance, although not true stem tubers as they lack “eyes” on them. They are primarily for moisture storage and can store a great deal of water.

Only the leaves are above the surface. A mature plant’s leaves can reach three feet (90 cm) in height. The leaves are pinnately compound like those of an ash tree (Figure 2). Many people incorrectly refer to the leaflets as leaves and the leaf stalk or petiole as its stem. In actuality, the only stems are the underground rhizomes.

ZZ plants are native to East Africa, where they are apparently rare. Summer Rayne Oakes, a YouTube video host did a repotting video with help from her guest Allan Schwarz, founder of Mezimbite Forest Center in Mozambique. Schwarz, who spends a considerable amount of time in the region, confided he had never seen one in the wild (Oakes, 2019).

Cultural Requirements
This is a versatile plant, preferring bright indirect light, but is also very tolerant of low light conditions and can survive in the latter for quite considerable periods of time. This isn’t a good long-term strategy, however, and if you really want one in a dark corner, it’s probably best to have two plants, with the second in a brighter location, and rotate them every few months.

The plants are able to tolerate considerable periods without watering, especially in low light. In bright light, they can be watered once or twice per month—not more!—but in low light they should go for a month or longer between watering. I have heard people say they water theirs as little as once every three months, although I wouldn’t advise going to this extreme. When you do water, do so thoroughly and allow the plant to take up the water to store. This mimics the conditions it grows under in its natural habitat.

ZZ plants do best in well draining soil. I generally use two parts of a commercial potting mix and one part perlite. As potting mixes generally have some perlite in them already, this results in slightly more than a third perlite.

Pests are rare, although one plant I was given did have a small infestation of scale insects. These were quite easily controlled by swabbing with rubbing alcohol and weekly applications of insecticidal soap for a couple of months. It has been over a year since I last saw any scale. This really is one of the least pest-prone plants you can find.

Perhaps related to their relative lack of pest problems, there is a concern, as with other aroids, about ZZ plants’ toxicity due to the presence of calcium oxalate crystals, not only in their sap but in all parts of the plant including the leaves, petioles, roots and rhizomes. Gaumond (2022) has stated, “The plant mainly causes irritation if touched or consumed, leading to stomach pain, vomiting, and lack of appetite in pets.” In fact, calcium oxalate crystals are microscopic insoluble sharp crystals, much like tiny knives. When skin, lips or mucosal surfaces such as anywhere in the mouth and digestive tract, or eyes are exposed to calcium oxalate crystals moderate or severe irritation can occur leading to pain and swelling of the area. Although rare, airway swelling and damage to the digestive tract can have serious consequences. This is of particular concern to children and pets who may try to chew the plant, which should always be kept out of reach. If you cut your plant for propagation, either wear gloves or carefully wash your hands afterward to avoid getting sap into your eyes or on your skin or lips.

Propagation
Propagation can be accomplished by division of the plant, from leaf cuttings and even leaflet cuttings. Note, however, the latter two methods are very slow to establish. I have one that took three years to finally grow one new leaf, although the root growth was more rapid. By contrast, division of the rhizome can result in quite a bit of new top growth.

If you’re a successful ZZ plant parent, the time will come when your plant will outgrow its pot and eventually it becomes a challenge to find successively larger pots. At this time, division becomes almost necessary. I have only divided one plant, a friend’s plant that had outgrown its pot. Before our session, I watched a couple of YouTube videos for instruction, one of which showed use of a handsaw to cut through the roots and rhizomes! We didn’t resort to that extreme, but did use her large carving knife and wound up with three substantial divisions, one of which became mine as a thank-you for helping.

Cultivars
As with so many plants in cultivation, mutations turn up from time to time and horticulturists have found several and named them. Cultivars in my collection include:
Z. zamiifolia RavenTM, a nearly black-leaved form, with the new leaves being green to begin with, darkening as they mature. This is the most commonly sold cultivar, and until recently tended to sell out very quickly at stores carrying it
Z. zamiifolia ‘Zenzi’, a dwarf form, is occasionally seen in specialty houseplant stores.
Z. zamiifolia ‘Zamicro’, a small, narrow-leaved form, is rarely seen. I bought a division from a hobbyist who I believe had divided his plant.
There are also variegated forms. Most of the cultivars are at least somewhat smaller than the wild form, Z. zamiifolia.

A more satisfying plant is hard to find and I heartily recommend it for the indoor gardener.

All photos by Robert Parsons

References:
-Children’s Hospital of Philadelphia, Poison Control Centre, Plants That Irritate.
https://www.chop.edu/centers-programs/poison-control-center/plants-irritate
-Flora of North America Online. http://floranorthamerica.org/Property:Etymology
-Gaumond, Andrew. 2022. Are ZZ Plants Toxic or Poisonous to Humans and Pets? https://www.petalrepublic.com/zz-plant-toxicity/
-Horwood Catherine: Potted History: The Story of Plants in the Home. Frances Lincoln Ltd. 2007; p 173. ISBN 978-0-7112-2800-9.11.
– New Edition: Horwood Catherine: Potted History: How houseplants took over our homes. Pimpernell Press Ltd., 2021. ISBN 9781910258941.
-Oakes, Summer Rayne. 2019. Repotting a Monster Zamioculcas zamiifolia (ZZ Plant)! YouTube video.

Published:  January 2023