Dieffenbachia: The June 2021 Houseplant of the Month

by Larry Hodgson

Dieffenbachia, or dumbcane: for many of us, it’s a name with a lot of history. Maybe our grandparents had one when we were kids or there was a big one in the darkest corner of the school or church we used to attend. Indeed, it’s one of the oldest houseplants of all, Dieffenbachia seguine having been introduced to Europe in 1759! It remains to this day one of the most popular indoor plants, not just in sales, but also as a hand-me-down plant, for this hard-to-kill houseplant is frequently passed on from generation to generation.

Origin

The genus Dieffenbachia is named for Joseph Dieffenbach (1796–1863), Head Gardener of the botanical gardens in Vienna.

The genus Dieffenbachia (pronounced dee-fun-BAA-kee-uh or dee-ef-fun-BAA-kee-uh) is native to Central and South America, from Mexico and the West Indies to as far south as Argentina.

It’s in the aroid family, and thus a close relative of other popular indoor plants such as the philodendron, the anthurium and the peace lily (Spathiphyllum).

The dieffenbachia closely resembles the Chinese evergreen (Aglaonema spp.), of the same family, but from the other side of the world: tropical Asia. The two evolved independently, but came to occupy a similar niche and, as is often the case, took on many of the same characteristics. It’s thus a case of convergent evolution. In general, dieffenbachias are larger, faster-growing plants than Chinese evergreens with broader but fewer leaves, often showing a considerable length of leafless stem at the base.

About 55 species of Dieffenbachia are presently recognized, but well over twice that many are waiting to be confirmed, plus there are over 150 cultivars: man-made hybrids or mutations that appeared in cultivation. Since dieffenbachia stems and leaves don’t dry well, the usual means of comparing them—that is through dried herbarium specimens—don’t readily reveal their differences, making proper identification difficult. 

In general, dieffenbachias are understory plants in humid to wet tropical forest: in other words, they’re jungle plants. In the wild, they’re often very abundant and visible, easily recognizable even to beginning gardeners due to their characteristic large leaves. They tend to form colonies, with all the individual plants being clones, having rooted from prostrate or broken stems.

Dieffenbachias almost never grow in full sun in the wild and are often found it deep shade. They’re most abundant in moist soils, even swampy conditions, although they may undergo seasonal droughts.

Habit

Dieffenbachias are herbaceous perennials with a thick, straight, upright stem and large, pointed elliptic leaves up to 3 feet/1 m long, most often mottled in varying degrees with white, light yellow or pale green markings or with highlighted by similarly contrasting veins. The leaves grow in a spiral pattern and are borne on a thick petiole that wraps around the stem at its base. The wide stems are often called canes.

Although the stem may look like a trunk, there is no bark nor lignin (wood). It is clearly ringed with nodes indicating where leaves were formerly attached and is usually green or variegated. Typically, the stem will reach from 3 feet/1 m in height in the case of thinner-stemmed species to up to 12 feet/3.5 m (thick-stemmed species), but eventually bends over to the ground where it then roots and produces offsets. In the wild, prostrate stems are then often broken by animals and each piece produces a new plant. This is the dieffenbachia’s main means of propagation in the wild. 

Indoors, where there is no wind to topple it, some specimens can grow to up to 26 feet/8 m, although their upright growth is limited by the height of the ceiling in most home settings.

Flowering is usually unobtrusive and indeed, many people mistake the green inflorescence for a leaf that has failed to fully unfurl. This “leaf” is actually a spathe inside which is found the spadix (flower spike) that contains the tiny flowers. In most species, only the top part of the spathe unrolls, thus only the tip of the spadix is exposed.

If you were to take a dieffenbachia inflorescence apart, you’d discover male flowers at the top in the exposed part with female ones hidden below inside the spathe, often with a section of bare stem in between the two.

The inflorescence is usually only viable for 24 hours, during which time it gives off heat and emits an odor, a combination that attracts pollinating beetles. Given the absence of appropriate pollinating insects in the home environment, seeds are almost never produced. Flowering can occur at different times of the year, depending on the species.

So, Just How Poisonous Are Dieffenbachias?

Well, their toxicity is certainly well known. They get their common name “dumbcane” from the fact that the toxic calcium oxalate they contain can cause swelling of the throat if ingested, temporarily preventing the victim from speaking. Biting into a leaf causes an immediate painful reaction in the lips, tongue and gums, with the result that the victim usually spits it out instantly. It’s perhaps for that reason that dieffenbachias so rarely cause serious poisoning. One study found, of 188 poisonings, all were minor and required either no to only very minor medical treatment. Tellingly, 70% concerned children under five. 

Most cases of poisoning in adults come from people (dare I say stupidly?) wanting to test whether it’s true chewing on one can render you dumb. Indeed it can, and painfully so at that. Plus the effect can last several days. Just don’t do this!

Dieffenbachias are also toxic to most pets, although again, serious poisoning almost never occurs. Clearly, though, they have to be kept out of reach of children and pets.

The skunky smell released when dieffenbachia tissues are damaged probably acts a warning to animals that chewing on the plant is probably not a good idea!

Assortment

There is considerable confusion in the naming of dieffenbachias. Many species have changed names over the years, sometimes several times, and may be sold under different denominations, nor can I claim that I’ve managed to straighten things out entirely in the text below. Hopefully, I’m not too far off!

There are really two categories of dieffenbachias these days: the tall, treelike varieties that grow upwards and never divide at the base unless forced to by harsh pruning, mostly older varieties, and newer compact varieties, that naturally form clumps and give a fuller appearance, although they’re not as robust as the big ones, with thinner leaves that aren’t as resistant to dry air.

Here are a few of the more commonly grown species and cultivars:

Dieffenbachia seguine: Under this name, I’m including a whole host of dieffenbachias often sold in the horticultural trade under such names as D. amoena, D. maculatum and D. picta, but now brought together under this name, largely based on studies of Dr. Thomas B. Croat of the Missouri Botanical Gardens. This was the first dieffenbachia ever collected and, in its various forms, remains the most popular in cultivation as well. It is found in the wild in Northern South America and throughout the West Indies. Similar species, like D. oerstedii, replace it in Central America.

It’s a tall species, frequently reaching 6 feet (180 cm) or more, with large, thick leaves variously marbled with cream and greenish yellow on either side of a thick central vein. Like most tall species, it’s not given to producing offsets at its base, nor does it branch much when cut back, but will instead usually produce a single new cane.

D. seguine ‘Amoena’: Once considered a species in its own right, it is now largely believed to be a selection of D. seguine, which it resembles, although it does show a bit more variegation.

D. seguine ‘Tropic Snow’: Probably even more popular today than its parent, of which is a more colorful version with heavier variegation.

D. ‘Camille’: Popular cultivar with creamy-yellowish leaves, fading to white in the center, surrounded by a green margin. Distinctly bushy habit.

D. ‘Camouflage’: Clumping variety with large leaves, mostly greenish yellow with occasional splotches of dark green and gray green.

D. ‘Carina’: This larger variety has medium-green leaves speckled with light green and splotches of darker green. Clumper.

D. ‘Compacta’: One of the original clumping types. Medium green leaves, heavily marbled with creamy yellow except along the edges.

D. ‘Delilah’: Striking creamy-white leaves, long and fairly narrow, bordered in dark green.

D. ‘Honeydew’: This larger variety has golden-yellow leaves, often with only the most modest green margin.

D. ‘Mary’: A fast-growing variety with rather narrow light-green leaves with dark green and creamy-green marbling.

D. ‘Memoria Corsii’: An older tall selection whose dark green leaves have an almost silvery overlay, topped off by irregular white spots. Its coloration varies widely according to light conditions.

D. ‘Nelly’: Small variety that branches readily. Slow-growing and thus sometimes used, when young, in dish gardens. Cream and green variegation.

D. ‘Rebecca’: A compact clumping variety with bright yellow-green leaves, mid green edges and some green marbling.

D. ‘Sarah’: Mostly creamy white to green with larger mid-green splotches.

D. ‘Snow’: A big one, with very dark green leaves overlaid with silvery green and creamy-white spots.

D. ‘Sparkles’: Light green leaves splattered with dark green and white on a smaller, clumping plant.

D. ‘Sterling’: An unusual variety without the marbled variegation we expect from dieffenbachia. Instead, the dark green leaves are highlighted by a thick white midrib and further enhanced by white veins. Quite large, but a slow grower.

D. ‘Star Bright’: Fairly narrow leaves in golden yellow with a thin green border and small green splotches.

D. ‘Tiki’: A big one with intriguing leaves due to their ruffled edges. They’re mostly mid green spotted with gray, green and white.

D. ‘Triumph’: Quite large leaves in creamy white with dark edges and a white central vein. 

D. ‘Tropica Marianne’: A medium-sized variety with large creamy-white leaves and only narrow green edges.

Caring for Dieffenbachias

Dieffenbachias have the reputation of being low-care plants and they largely live up to that expectation. 

Light: Despite the dieffenbachia’s reputation for being low-light plants, they actually do best in medium light or even bright light: either under filtered light most of the day or good light at all times, including some direct sunlight, although with protection from the burning midday sun. They can adapt to full sun indoors, but may well burn outdoors under that condition. The best choices for low light are the big ones like D. seguine and its relatives: I’ve seen some decades old growing (slowly) in some incredibly dark places! 

Helpful Hint: Do give dieffenbachia a quarter turn regularly so they receive light from all sides; otherwise they’ll lean towards the light. Not only does that take away from their attractiveness, but if they lean far enough, they’ll likely topple over.

Watering: Keep the soil relatively moist, watering well when the soil becomes a bit dry. They will take drier conditions, but don’t thrive in them. They slow down considerably in the winter, but never really stop growing, so will still need reduced but regular watering at that season.

Humidity: They all prefer high humidity, but the thicker-leaved ones adapt well to 40% humidity or even a bit less. 

Fertilizer: Don’t waste your money fertilizing these plants too abundantly: it doesn’t speed up their growth or improve their appearance to any appreciable degree. (If you want faster growth, especially, give them more light!) They’ll do fine with no fertilizer whatsoever, especially the tough-as-nails D. seguine and its selections, but a bit of light fertilizing during the spring and summer, at 1/8^th of the recommended dose, will probably give them a bit more vigor.

Temperature: Dieffenbachias don’t like the cold and should be kept warm at all times, even in the winter, ideally above 62?C (17?C) at all times. At temperatures below 50?C (10?C), some varieties are severely damaged. They tolerate no frost.

Grooming: After a while, dieffenbachias seem to reach a sort of stasis: although they continue to grow in height, for every new leaf they produce from then on, an older one will turn yellow and die. Just remove and put it in the compost (no, dieffenbachia leaves will not make the compost poisonous!). If many lower leaves turn yellow at once, consider whether the plant has recently been moved to lower light and is therefore adapting to the change or if it is being under- or overwatered.

You can cut off the flowers if you want: they add little to the plant’s appearance.

Repotting: Dieffenbachias are generally slow to very slow growing, but still, will eventually need more space for their roots and thus repotting. Every two or three years is usually fine. You can repot at any time during the growing season, basically from late winter to early fall. Standard potting soil is fine for this easy-to-accommodate plant. Any pot with a drainage holes will do, ideally one a few inches (5 cm or so) larger than the previous one. If the plant is getting tall and top-heavy, it may be wise to use a weightier container: terra cotta, ceramic or concrete, perhaps. Or to slip a lighter plastic pot into a heavier outer one. 

If you can’t repot—and once yours has reached a considerable size or has been planted in a very large pot, repotting becomes awkward if not impossible—, try top dressing: scraping off the top inch or so (about 3 cm) of soil and replacing it with fresh soil. Do this annually to keep mineral salts from building up in the soil to dangerous levels.

When pruning dieffenbachias, it’s best to wear gloves and eye protection. Not that the dieffenbachia’s toxic sap will harm your skin (just rinse it off when you finish), but you don’t want it to come into contact with your eyes or mucus membranes.

Cutting Back: Dieffenbachias do not conveniently stop growing when they’re just the ideal size. They keep getting taller and taller, with all the foliage at the top and an increasing length of bare stem at the bottom and middle. When they are no longer attractive—and certainly when they can no longer support themselves—, it’s time to consider cutting them back.

Many gardeners seem reluctant to do. One often sees tall, arching, forlorn-looking dieffenbachias leaning on walls or fixed to stakes with twine, even bending in contact with the ceiling, and the effect is far from attractive. There really is no reason to put up with this when the problem is so easily solved. 

Cutting back will stimulate a fresh flush of new attractive new growth and make your plant attractive again. If there are several stems, you can even stagger the pruning, cutting back one stem about every two months so you won’t have the plant looking like a pot full of stubs until it regrows. 

The part removed can also be used as a source of cuttings (see below). Or you could air layer the top, rooting it before you remove it, making its transition easier.

You often see people simply cut off the top of the plant fairly near the ceiling, leaving at tall bare stem from which a new sprout soon appears … but with the result that it is soon as top-heavy and graceless as before. It’s best to cut such ungainly plants back severely to force the plant to regrow back from the base.

Cut back to about 4 to 8 inches (10 to 20 cm) from the bottom, about ¼ inch (0.5 cm) above a node (mark where a leaf was once attached), at a right angle. Yes, this will leave your plant looking like nothing more than a stub, but … it will soon start growing again and fill in.

You can do this again and again. Some families have hand-me-down dieffenbachias they’ve been maintaining like this for generations!

Multiplication: Commercially, dieffenbachias are almost always grown by tissue culture: a few cells from the meristem are harvested and grown in a laboratory flask, then grown into thousands of identical specimens. They’re true test tube babies! But that’s not practical in the home, nor is growing them from seed, since seed is almost never available unless you have plants growing outside in a tropical climate where the appropriate pollinating beetles live. 

Instead, dieffenbachias are usually multiplied either by air layering, tip cuttings or stem section cuttings. 

All these techniques are best carried out in early spring.

Air layering involves making a small cut in the stem, wrapping the wound in moist sphagnum moss, then in plastic wrap, then waiting until roots appear before you cut the top free and plant it on its own. There’s an article about air layering here that explains the procedure step by step: Air Layering: Taking Big Houseplants Down a Notch. 

That said, air layering is not really necessary, as dieffenbachias root so readily from simple tip cuttings. 

You can root them by taking a stem tip cutting: cutting off the top of the plant about 6 inches (15 cm) below the lowest leaf and inserting the stem into a pot of moist potting mix. No rooting hormone is necessary. Seal the entire pot inside a large plastic bag (don’t worry, the cutting will be able to breathe!) to maintain high humidity and prevent leaves from wilting, then place in moderate light. After about two months, open the bag and give a light tug. If there is resistance, the stem has rooted and is officially an independent plant. Acclimatize the plant to the drier outside air by opening the bag bit by bit over a few days, then remove it entirely and place your new plant pretty much wherever you want.

You can also root a dieffenbachia stem cutting in a glass of water, although this can be awkward with larger varieties, as they’re heavy and likely to tip over. Plus the leaves tend to wilt and droop, a clear sign of their stress. Also, as soon as roots start to appear, pot up rapidly, as roots remaining too long in water adapt poorly to soil. Rooting in water is essentially just a more complicated and riskier way of multiplying the plant compared to rooting it in soil from the start. 

Now, if you’ve just cut off the top of your dieffenbachia in order to root it, that will leave you with a long section of bare stem … that you can also use for multiplication, taking root section cuttings. Chop the bare stem into sections, each with at least 3 nodes. That could be about 3 to 8 inches/7 to 20 cm, depending on the spacing of the nodes, as some plants have tight internodes, others wide ones. These leafless stem section cuttings look like so many small green logs, but still root … slowly. It’s important to remember which side goes upwards if you plant them vertically, because a cutting planted upside down won’t root. But you can also plant the stem cuttings on their side, burying the bottom half in moist soil, but leaving the upper part exposed. Even from its prone position, the stem’s hormones will tell it to send new roots downwards and the new stem upwards! With time, each stem section will produce a new plant.

And now you have a problem: what are you going to do with all the dieffenbachias you’ve produced?

Growing Dieffenbachias Outdoors

Although this article is about houseplants, clearly dieffenbachias can be grown outdoors as well, either during the summer in temperate climates (once the air has thoroughly warmed up), or year-round in tropical areas (USDA hardiness zones 10 to 12). Outdoors, they will certainly need protection from full sun and are best grown in filtered light or moderate to deep shade. Protection from wind will help prevent leaf damage.

Problems

Besides dealing with overgrown, top-heavy dieffenbachias (read Grooming above for solutions to that problem), there are other complications that you may need to deal with. 

Diseases: There are various diseases that can attack dieffenbachias, most limited though to situations of extreme humidity, such as a production greenhouse, and not likely to spread under average home conditions. Do carefully inspect new plants before purchase, though: if you see any signs of rot, soft tissue or discolored circles on the foliage, simply don’t buy the plant. And isolate plants after purchase for at least 40 days before putting them near your other plants.

Rot, usually occurring at root level or on the lower stem, is the one disease problem that does seem show up even under average home conditions and it’s usually linked to overwatering or keeping the soil too moist, especially in winter. You may need to restart a plant rotting at the base from a cutting … and in the future, keep the potting mix a bit drier so it doesn’t happen again.

Pests: Also check new plants for insects before purchase and isolate them when you bring them home. Aphids are occasional pests and can usually be controlled by spraying with insecticidal soap, as can spider mites, the latter most prolific when the air is dry. 

Mealybugs and scale insects, though, are not so easy to control. They can easily hide at the base of the plant’s leaves and therefore just when you think you’ve eradicated them, they’re ba-ack! Try the following to get rid of them:

Cut the plant down to a stub, as explained in Cutting Back, thus ridding the plant of the bugs’ main hiding place: leaf axils. Carefully wipe down the stub as well as all exposed parts of the pot with a rag dipped in soapy water … and put the plant in isolation. Chances are, when it grows back, the mealybugs and scale insects will be gone.

Guttation: Finally, do be aware than dieffenbachia leaves sometimes drip sap that can fall onto the floor or table below. This is called guttation and is usually linked to keeping the potting mix too moist: it’s one of the plant’s ways of ridding itself of excess moisture. Try letting the growing mix dry out a bit more before watering and the problem should correct itself.

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Dieffenbachias: tough, attractive and easy-to-maintain foliage plants. They may just be the thing your décor needs!