Dumb Cane is a resilient houseplant that makes a good choice for beginners. But you still need to get the fundamentals right if you want it to stay healthy, and few things are more fundamental for a plant than sunlight. So how much light should a Dieffenbachia get? And can you ever grow one outdoors?
Dieffenbachias thrive in indirect sunlight, so they’re better off in partial shade than full sun. You can keep yours outside as long as you ensure that it’s shielded from direct sunlight (and bring it back inside before the weather turns cold). If your Dumb Cane sits in full sun for more than an hour or two, its leaves will burn, and its health will suffer.
Though many care guides mention that Dumb Cane is very shade tolerant, there is such a thing as too little light. In particular, cultivars with lots of brightly colored variegation require a good amount of indirect light to maintain their spectacular markings. If you’ve noticed that your Dieffenbachia leaves are looking dull and dark, you should probably move it to a brighter spot.
Light Requirements For Dieffenbachia
Like many houseplants we discuss on this site, Dumb Cane is a jungle plant first and a houseplant second. It will be happiest in the lighting conditions that prevail in the lower reaches of a tropical rainforest: lots of light, but very few rays falling directly on its leaves. Dieffenbachias prefer the dappled, shifting patterns of sun and shade produced by the sun shining through a leafy canopy.
In the usual jargon of plant nurseries and gardening guides, a Dieffenbachia does best in bright, indirect light. “Indirect” means light that’s reflected off or filtered through another surface.
When you’re trying to find the right spot for your Dumb Cane, one simple trick is to look at the shadows. If they’re bold and dark, with clear, sharp edges, the sun is too direct and intense for a Dieffenbachia. On the other hand, if they’re so indistinct that you can’t make out their shape, the light is probably too dim. The sweet spot is one where the shadows are visible, but weak, with slightly fuzzy borders.
There are also nifty tools called illuminance meters that can precisely measure how intense the light is in any given area. You’re looking for somewhere between 1,000 and 2,000 foot-candles. (Yes, a foot-candle means the amount of light cast by a candle from one foot away. Sometimes science is whimsical that way.)
You’ll have to do a bit of experimenting to find the perfect location, but we can offer a few tips to point you in the right direction. Try placing your Dumb Cane:
- 4-6 feet away from a window that faces west or south. The light that’s coming through should be bright enough to nourish your plant, but it will be arriving at an angle that stops it from hitting the leaves dead-on.
- Right next to a northern or eastern window. Northern windows never get any direct light, and eastern exposures only face the sun in the early morning. During those cooler hours, your Dieffenbachia can handle a little sunbathing.
- Behind a semi-translucent curtain. Sheer fabrics like linen or lace take the edge off the sunlight without blocking it out completely. A set of Venetian blinds left half-open will do the same. You can pop your plant right in a south-facing window if you’ve got the right blinds to protect it.
Keep in mind that the advice above about the direction of exposure only applies if you live in the Northern Hemisphere.
How to Tell if Your Dumb Cane is Getting Too Much Sun
It will probably take a bit of messing around to find the ideal home for your Dieffenbachia. In the meantime, pay close attention to your plant’s health to make sure it’s not suffering.
It’s often pretty easy to identify a Dumb Cane that’s been in the sun too long – because it will have a nasty sunburn. Sun damage in plants causes dry, brittle, browning patches on the foliage. More mildly scorched areas may appear faded and pale rather than brown.
This happens because the heat of the direct sun makes your Dieffenbachia release water from its leaves more quickly than normal. After a while, the cells begin to run out of moisture until they shrivel up like raisins, creating those crispy dead spots. This also makes the leaves wilt and droop as they’re deprived of the water they need to stand firm.
Even when your Dumb Cane isn’t actually getting sunburned, an overly bright environment may make its coloration lighter than you’d prefer. These plants adjust their level of variegation depending on their surroundings; when they’re flush with light, they don’t produce as much green tissue. So if you prefer a vivid contrast in your Dieffenbachia’s markings, aim for a balance of light and shade.
Temperature, Humidity, and Sunburn in Dieffenbachias
Sun scorch isn’t the only problem that might cause your Dumb Cane’s leaves to get withered and brown. Lack of humidity can have similar results, as can temperatures in excess of 85-90 degrees; both result in the same dehydration effect discussed above.
One way to tell the difference is by looking for dead spots that appear in the middle of the leaves or cluster on the surfaces with the most sun exposure. When the side of a plant facing the nearest window is covered in brown tissue, you can bet it’s a sun issue. By contrast, a humidity shortage often dries out the edges of the leaves first.
That said, these issues can and often do work in tandem. Hot and dry air renders your Dieffenbachia more vulnerable to sunburn. If you’re worried that the plant may be in a location that’s a little too sunny, try to keep it cool and moist.
One handy way to boost the humidity level is to group your Dumb Cane alongside other tropical plants. As they all shed moisture from their leaves, they’ll create a tiny zone with higher ambient humidity than the rest of your house. You can also set your Dieffenbachia on a humidity tray – a flat-bottomed tray filled with pebbles and a shallow layer of water – to provide a bit of extra moisture through evaporation.
Finally, an electric humidifier is far and away the most effective way to combat dry air in Dieffenbachias. If you spring for the kind that can shift between warm and cool mist, you can also get a small amount of temperature control to help the plant out on hot days. This will give it an extra buffer against sun scorch.
Reviving a Sunburned Dieffenbachia
Your Dumb Cane’s overall health will bounce back once you get it out of the harsh rays that are stressing it out. However, sun damage in leaves is permanent, so there’s nothing you can do to fix the areas that have already been burned.
If you don’t want to stare at a bunch of ugly brown patches, you can prune them away; just try not to remove any parts that are still green. Your Dieffenbachia needs that healthy tissue for photosynthesis, which will enable it to grow new and healthy leaves. When you’re trimming your plant, always disinfect your pruning scissors to avoid causing an infection.
If your Dieffenbachia has lost a substantial amount of foliage, you’ll want to scale back on fertilizer while it’s recovering. And keep the plant away from all direct sunlight for at least a few weeks.
How to Tell if Your Dumb Cane is Getting Too Little Light
As we noted earlier, Dieffenbachias do need a certain amount of light to thrive. However, they’re a lot more tolerant of dim lighting than excessive sun. Unless you lock your plant in a closet, it probably won’t die from lack of light.
But you don’t just want your plant to survive, do you? You want it to grow big and strong, putting out lush and vibrant foliage. And that won’t happen if it’s not getting enough sunlight. You need to give your Dumb Cane a decent amount of illumination to help it live up to its potential.
The first indicator of a sun-starved Dieffenbachia is abnormal growth. When they receive plenty of light, water, and nutrition, these plants will produce bushy foliage and thick, robust stems. But when they’re not getting their recommended daily serving of sun, they’ll stretch upward in hopes of snagging a stray beam.
The result is a “leggy” plant – the stem is unusually tall and skinny, with the leaves widely spaced and mostly clustered at the upper end. This can cause a Dieffenbachia to droop and tilt as it becomes top-heavy. Depending on where the nearest light source is, the plant may also twist into odd shapes as it tries to aim itself for maximum exposure.
In Dieffenbachia varieties that generally display a lot of light-colored variegation, a shift toward darker hues can be another indicator of low light. When the plant isn’t getting as much sun, it will get greener, trying to soak up as many photons as possible by making lots of chlorophyll. This doesn’t always mean your Dumb Cane is in poor health, but if you like its leaves better with splashes of bright color, you’ll want to move it into a better-lit environment.
Grow Lights for Dieffenbachia
If you’re having trouble finding a place in your home that gives your Dieffenbachia the light it needs to grow, you can always bring in some outside help. Full-spectrum LED grow lights produce the right wavelengths to nourish your plant without scorching it. We prefer the Sansi 15W LED bulb, which is fairly inexpensive and can be placed about a foot away from most plants with no risk of heat damage.
As with most aspects of plant care, you’ll probably have to do some tinkering to get the levels right. A good rule of thumb is to give it 6-7 hours a day under the lights if you think your Dumb Cane only needs a little extra juice. If the room is really dim and the plant will be getting most of its nourishment from the lamp, you may need to keep it lit up 12 hours a day or more which can be simply automated with an outlet timer.
Keeping Dumb Canes Outdoors
Many houseplant owners like to let their leafy friends play outside when the weather is nice. You can move your Dieffenbachia onto your balcony or into your garden during the summer – as long as you take some sensible precautions.
The first and most important thing is to place it somewhere shady. There’s little chance of your Dumb Cane being under-lit; even a fairly sheltered area in the Great Outdoors will generally receive more photons over the course of a day than a similar spot in your living room. Sunburn is a much more pressing concern.
The best solution is to keep your Dieffenbachia directly in the shade of some taller plants. This is about as close you can get to the lighting conditions in its natural habitat. If that’s not an option, the shade of an overhanging patio roof or garden umbrella will also do nicely.
Don’t rush the transition, either. Your Dieffenbachia is an indoor kid, and it needs time to acclimate to being outside. As the weather warms up in the early summer, start placing your plant outdoors for an hour or two each morning before bringing it back inside. You can make these little jaunts a bit longer each day, and by the time the summer is in full swing, your Dumb Cane will be at home in the outdoors.
Be careful to take it back inside before the weather starts to get chilly. These plants are quite sensitive to even brief drafts. If you think the temperature is likely to drop below 60 degrees Fahrenheit or so, summer vacation is over for your Dieffenbachia,
A Dieffenbachia will do better in a location that’s a bit too shady than one that’s a bit too bright. In the end, though, it’s going to be happiest when it gets lots of indirect or filtered light.
Exercise caution, but don’t be afraid to experiment. As you get to know your plant better, you’ll get a feel for the type of lighting that will keep it healthy and beautiful.