When you take good care of a Dieffenbachia, it can grow until it towers over your furniture, creating a little slice of the jungle inside your home. But in an indoor environment, it’s not always easy to nurture your plant to its full height. That’s why we’ve put together this list of tips for encouraging a Dumb Cane to grow tall, full, and strong.
Sunlight is the most crucial factor in a Dumb Cane’s growth, so keep yours in a bright spot. It’s also important to water it well and provide some fertilizer to supplement its diet. Keep the humidity above 60% when possible, and repot your Dieffenbachia into larger containers on a regular basis.
Healthy Dumb Canes usually grow at a rate of roughly 2 feet per year. If your plant seems to be slacking, it’s probably not getting enough of a crucial growth factor such as water or sunlight. Don’t hesitate to look back over this list to get an idea of what your Dieffenbachia needs! Here are our 7 tips for growing a giant Dieffenbachia.
#1: Choose the Right Kind of Dumb Cane
Dieffenbachia isn’t just one plant – it’s an entire genus that contains more than 50 species, including dozens of different varieties that are commonly grown as houseplants. Their maximum size can differ quite a bit between variants. If you’re hoping to grow a monster Dumb Cane, you’ll need to select a cultivar with the right potential.
Here are a few examples of larger Dumb Canes, all of which are capable of growing 6-10 feet tall in the right circumstances:
- Dieffenbachia seguine. This is one of the more common varieties, and the most likely to be sold simply as “Dieffenbachia”. It features wide leaves with narrow white bands on a dark green background.
- Dieffenbachia Snow. Subtle but beautiful, with vivid speckles of silver and white dotting its foliage.
- Dieffenbachia Honeydew. One of the brighter varieties, the Honeydew’s leaves are bright yellow at the center, fading to lime green, with a darker green band encircling the outermost edge.
- Dieffenbachia Mary. Known for growing rapidly, this cultivar is a good choice if you don’t want to wait long for a gigantic Dumb Cane. Its dazzling leaves are dappled with a chaotic spray of deep green and yellow.
On the other hand, you’ll want to avoid these varieties, which have been bred to fit in smaller spaces:
- Dieffenbachia Compacta. The speckled appearance is very similar to the Dieffenbachia Mary, but this one won’t reach much higher than 3 feet tall.
- Dieffenbachia Camille. This shorter cultivar has a bold flame of creamy white in the center of each leaf, appearing wider if the plant is getting a lot of light.
- Dieffenbachia maculata. Quite compact, with pointy, variegated leaves.
- Dieffenbachia Tropical Tiki. This is a variant of D. maculata that includes some subtle silver-gray markings along with the more common green and white.
Choose your plant wisely – it’s a lot harder to grow a big Dumb Cane if you’re fighting against its genetics!
#2: Lighting is Key
Any bodybuilder will tell you that you can’t put on mass unless you’re consuming plenty of calories. That’s true of your Dumb Cane, too, only its calories come from sunlight instead of steak and quinoa. Sadly, inexperienced indoor gardeners often place their Dieffenbachias in dimly lit rooms and then wonder why their plants look scrawny.
This mistake probably results from concern about the dangers of direct sunlight. Dumb Canes have thin leaves that burn easily when the sun’s rays hit them head-on. But that doesn’t mean they like to live in the dark; it just means that they can’t sit right next to an unshaded south-facing window.
To help your Dieffenbachia grow strong, leave it in a location where the ambient sunlight is bright enough that you can read the fine print on your cell phone bill. An east-facing window is often a great choice because it will be brightest when the air is coolest, reducing the risk of sunburn. If the room has mostly southern or western exposure, keep your Dieffenbachia 3-6 feet from any windows, or hang semi-opaque blinds to give it some cover.
It’s also a good idea to rotate your plant’s pot every 3-5 days to let it get sun from all sides. This will help your Dumb Cane stay well-rounded instead of tilting toward the light.
#3: Don’t Dehydrate Your Dumb Cane
Some houseplants begin to droop, shrivel, and grow crispy as soon as their potting mix dries out. Dieffenbachias aren’t so fragile, and they can often hang on for a surprisingly long time even in dry conditions. However, this resilience has a downside – it can lead their owners to get negligent with their watering, causing stunted growth.
Even if it’s not showing immediate signs of distress, a Dumb Cane in overly dry soil can’t grow. Every time you let the roots dry out completely, you’re bringing your plant’s growth to a screeching halt.
The best way to ensure that your Dieffenbachia has enough moisture to get big and tall is by keeping a close eye on the soil in its pot. You should water as soon as the top two inches of soil have dried out – at that point, there should still be a little bit of moisture in the bottom of the pot, but not so much that the roots will suffocate if you add more.
For extra certainty, you can test the lower portions of the soil with a thin wooden stick like a barbecue skewer. Poke it down to the base of the pot and leave it in place for about a minute before pulling it out.
If your probe comes back dry or only slightly moist, go ahead and water your Dumb Cane. If the wood is soaked through and covered in clinging soil, you can wait another couple of days. Don’t want to have to estimate the dampness of a wooden stick? You can use a soil moisture meter, which gives clear, easy-to-understand readings.
Whichever method you prefer, test your Dumb Cane’s soil roughly every 3-5 days. You can adjust this schedule somewhat throughout the year – your plant won’t use as much water in the winter, so it won’t need such frequent checkups.
#4: Make Sure Your Plant Takes its Vitamins
Light and water are the biggest drivers of growth, but your Dieffenbachia also needs the right blend of nutrients to produce healthy new leaves and stems. You’ll have to supply these in the form of fertilizer.
Houseplant fertilizer comes in many forms, but we generally recommend using the type that you can add to your Dumb Cane’s water. This requires more frequent application, but it allows for more precision with the dosage, allowing you to ramp it up or down according to the plant’s needs. This one is a great choice, as is any other option that provides a 2:2:2 ratio of nitrogen, phosphorus, and potassium.
You should only fertilize a Dieffenbachia when it’s actively growing. Unless you live in the tropics, that window will be limited to the spring and summer. Fertilizing once a month during the growing season is usually enough, and it’s often a good idea to start with half the dosage recommended on the packaging. Always remember that a fertilizer overdose will kill your Dumb Cane much faster than a shortage.
#5: Drainage Matters
We’ve explained how important it is to keep your plant properly watered and fertilized, but did you know that both tasks are a lot easier if you plant your Dieffenbachia in the right kind of soil?
The composition of the potting mix determines how fast moisture and minerals flow through the pot. A fast-draining soil is better – it’s less likely to get sludgy and smother your plant’s roots, or to accumulate harmful concentrations of fertilizer. Airy soil makes it easier to hydrate your Dieffenbachia and supplement its diet without going overboard.
The best soils are made mostly of large particles that leave space for water to flow through, along with enough spongy organic matter to keep the roots from totally drying out. Our go-to recommendation is a mix of 10% vermicompost, 25% coconut coir, 25% conifer bark chips, and 40% coarse-grain perlite. (Read more about the best soil for your Dumb Cane here.)
To get the best results from this potting mix, make sure to saturate it well every time you water. The entire mass of soil should be soaked through, with a bit of liquid running out from the base of the pot. This makes sure the roots are nicely hydrated, and it helps wash away excess mineral salts that your fertilizer has left behind.
It’s also a good idea to perform a more thorough soil flush every 1-2 months during the growing season. A soil flush is just like an ordinary watering except with much more liquid – use 4-6 times the total volume of your Dumb Cane’s container. Distilled water or filtered water is best for this purpose. (Only do this if your plant is properly planted in a container with a drainage hole in the bottom – which it should be!)
#6: Make Room for the Roots
When your Dumb Cane gets taller, wider, and leafier, it needs more water and nutrients, and its root system has to grow to keep up with demand. If the roots have nowhere to expand, your plant’s growth will grind to a halt both above and below the soil.
You’ll occasionally need to move your Dieffenbachia to a larger pot if you want it to keep getting bigger. We’d recommend transplanting every 2 years for maximum growth. The best time to repot is in the early spring.
Don’t go too big too fast. Giving your Dieffenbachia the houseplant equivalent of a McMansion will only increase the chances that you’ll overwater it, since moisture takes longer to evaporate from a large volume of soil. Each time you repot your Dumb Cane, give it about 20% more space than it had before (an easy rule of thumb is to pick a pot 2 inches larger in diameter).
One important reminder: always use a pot with drainage holes. If there’s nowhere for the water to go after it exits the soil, you’ll get the same problems as you would with overly dense soil.
Before you settle your Dumb Cane into its new home, check to see if it is root bound. This condition is easy to spot: it means that the roots are compressed into a tight mass in the shape of their container. Before transplanting, tease the crowded roots gently apart with your fingers to give them a bit more space to breathe. See our article on repotting Dumb Canes for more guidance.
#7: Moist Air for Healthy Growth
Because Dieffenbachias evolved in tropical rainforests, their version of the good life involves quite a bit of humidity. They don’t need an environment as muggy as the jungle, but if you can keep the ambient humidity above 60%, your Dumb Cane will thank you for it.
If you have the space and the budget for it, a portable humidifier is the best way to give your plant the moisture it needs. You can simply set the desired level and let the machine do the work.
There are also a couple of passive tricks that can help. One is to place your Dumb Cane in a room that’s already humid, like a bathroom or a kitchen. Another is to set it next to any other moisture-loving houseplants you own, creating a damper microclimate in one corner of your home. Placing the pot on a pebble tray also enhances the local humidity a bit.
Since humidity supports root growth, it’s especially helpful after you’ve just repotted your Dieffenbachia. Sometimes it’s a good idea to place a clear plastic bag over your Dumb Cane’s foliage or set the whole plant inside a glass terrarium while it’s recovering from being transplanted.
Most Dumb Canes will be happy to grow big and strong if conditions allow. As a matter of fact, many owners find that keeping them contained is the real challenge! If you supply the basic requirements for growth, you may have an enormous houseplant sooner than you expect. We hope our tips help you grow the giant Dieffenbachia of your dreams.