Does your Dieffenbachia seem to be stuck in a rut? Has it lost interest in gaining height and sprouting new leaves? As a concerned plant parent, you’re no doubt wondering why your Dumb Cane isn’t thriving and how you can help it recover. Fortunately, it’s often possible to get a sluggish Dieffenbachia back on track with one or two simple adjustments.
Dumb Canes have a few key requirements for growth: light, water, oxygen, and the mix of nutrients found in a houseplant fertilizer. If yours isn’t growing, it’s almost certainly short on one of those crucial ingredients. That could be due to poor watering habits, a less-than-ideal location, or stress.
This article will talk you through the main care mistakes that stop Dumb Canes from growing, starting with the most common ones before moving down to more unusual problems. We recommend reading through the entire list before jumping to a conclusion about what’s wrong with your Dieffenbachia. Several of these issues produce very similar symptoms, and a correct diagnosis will require you to consider every aspect of your plant care practice.
Do Dieffenbachias Grow Fast?
Before we talk about why your Dumb Cane isn’t growing, it’s important to understand what’s normal for these plants. After all, some slow-growing plants, like the very similar-looking Chinese Evergreen, may only put on a couple of inches of height each year. Is it unusual for a Dieffenbachia to grow slowly?
In a word: yes. Dumb Canes are prodigious growers in favorable conditions. It’s fairly normal for their stalks to shoot up two feet higher within a single year until they’re 6-10 feet tall. If yours is still at the same height as it was three months ago, it may be surviving, but it’s not living its best life.
That’s assuming you don’t have one of the more compact varieties. Some Dumb Cane cultivars have been bred to fit in more modest spaces than their giant cousins. It’s entirely normal for those types of Dieffenbachia to stop growing once they’re 2-3 feet tall. Popular examples include:
- Compacta. One of the first small-scale Dumb Canes. Its leaves feature bright white central veins that are surrounded by a chaotic spray of lemon-lime and dark green patches.
- Tropical Tiki. Its coloring is an intriguing mix of silvery streaks and snowy white speckles.
- Camille. Popular for its manageable size and the bold flares of creamy white and yellow in the middle of each leaf.
Bear in mind that Dieffenbachias grow very little during the fall and winter due to the reduced amount of daylight. It’s normal for them to wait until the spring to get any substantial growth going, though since they’re tropical plants, they don’t lose their leaves and go truly dormant even in the winter.
If you’re well into the growing season and your plant still seems to be languishing, you have a problem. Here are the main reasons your Dumb Cane’s growth may be on hold:
#1: It’s Hungry
Just like you, your Dieffenbachia has to take in energy to survive and grow. Unlike you, it absorbs its food in the form of pure sunlight. Every single calorie that a plant spends on growth must be supplied by the sun. Your Dumb Cane will be unable to get larger without a healthy amount of illumination.
Unfortunately, lots of houseplant owners choose these plants because of their reputation for being shade-tolerant and proceed to stick them in rooms that are far too dim. While it’s true that Dieffenbachias don’t like to be in full sun, they need bright, indirect light to flourish.
It’s not always obvious that your Dumb Cane’s growth is stunted by lack of light, because it might appear to be getting taller even in a poorly-lit room – but won’t be putting on any mass, so the stems will get long and skinny, with wide gaps between the leaves. New foliage may be stunted and lose its normal brightly-colored variegation. This growth pattern is known as etiolation, though many people just call it “getting leggy”.
If you suspect that your Dieffenbachia needs more light, try moving it closer to a window or into a room with more exposure to the sun. In the Northern Hemisphere, we get our sunlight from the southern skies. That means a space where the only windows face north may not be bright enough for your plant.
Try moving your Dieffenbachia to an east-facing window, where it can get some bright sunlight during the cool of the early morning. A southern or western window is good as long as your plant sits 3-6 feet back from the sill or you add a semi-translucent barrier like a thin linen curtain. See our article on lighting for Dumb Canes if you want more detail.
Don’t have enough window space for your Dumb Cane to thrive? You can supplement with some grow lights. Leave your plant under the lamps for 6-12 hours per day, depending on how badly it needs extra light.
#2: It’s Thirsty
The cells making up your Dieffenbachia’s body are about 90% water, so it should be no surprise that it needs hydration to grow. Even if your plant is getting enough water to keep it from shriveling up and dying, it may not have enough to climb higher and spread wider. If it’s badly dehydrated, its leaves will sag and wither, often turning yellow or crispy brown.
Sadly, there’s no universal watering schedule that’s perfect for every home and every Dumb Cane. Instead, you’ll need to check the soil periodically to see if it’s dry. These plants like their roots to stay a little bit damp at all times; although they can withstand brief periods of drought, they won’t be able to grow very much if you’re constantly letting them dry out.
The usual practice is to poke a finger into the soil every 3-5 days, watering your Dieffenbachia when the potting mix feels dry. Since the top couple of inches dry out first, this should keep the soil around the roots damp but not drenched – just the way your Dumb Cane likes it.
You can get even more accuracy by pushing a probe all the way down into the base of the pot. A barbecue skewer or chopstick made of unlacquered wood will do the trick – water when the stick is only slightly moist at the lower end. You can also get a soil moisture meter if you want even more precision.
#3: You’re Suffocating Your Plant
Our advice about keeping your Dumb Cane well-hydrated comes with an important caveat: it’s even more important to avoid overwatering. Dieffenbachia roots can’t function in an airless environment. When the potting mix retains too much water, they get smothered and can no longer do their job.
Ironically, this means that overwatering creates almost the same symptoms as underwatering, since your Dieffenbachia can’t take in water and nutrients. Often, this will make the foliage turn yellow, with the discoloration starting near the bottom of the plant and moving upward. Prolonged overwatering can also cause root rot by accelerating the growth of harmful fungi and bacteria.
When you suspect that your Dumb Cane’s roots are getting swamped, try giving it more time to dry out between waterings. Check all the way down by the roots (as described above) before giving it more to drink.
If the soil stays noticeably soggy for more than 4-5 days after each watering, you may have a problem with drainage. Make sure the holes in the base of your Dieffenbachia’s pot aren’t clogged and consider switching the plant into a chunkier, airier potting mix.
If your Dieffenbachia’s condition continues to get worse after you’ve let the soil dry, it could have a case of root rot. Mushy stems, foul odors, and swarms of fungus gnats are other possible warning signs. Take the plant out of its pot and trim off any roots that look dark or feel slimy, sanitizing your scissors with rubbing alcohol between cuts. We provide more comprehensive instructions on saving a Dieffenbachia from root rot here.
#4: Your Dumb Cane is Boxed In
Your Dieffenbachia’s expansion above the soil has to be supported by healthy growth down below. If there’s no room in the pot for the root system to spread out, your plant’s growth will slow down and stop.
It takes a while to get to that point. When the roots first reach the edges of the pot, they start curling back and overlapping onto one another, allowing them to continue lengthening for a while. Eventually, though, they’ll fill almost all of the space in the container, bunching into a dense mass with practically no room for air, water, or nutrients.
This is what indoor gardeners mean when they describe a plant as root bound or pot bound. This condition will stifle your Dumb Cane’s growth, and when it gets bad enough, the foliage will start drying out and dying off.
Identifying a root bound plant is fairly simple – all you need to do is lift it out of the pot. If the roots are packed in a tight cylinder, they’re pot bound. Gently work them apart, trim back the longest one with some disinfected snippers, and repot your Dumb Cane in a container that’s about 2 inches larger in diameter.
In the future, it’s better to be proactive about repotting. Switch your Dieffenbachia into a slightly larger vessel every 2-3 years. Read this article for step-by-step instructions.
#5: Your Dieffenbachia is in Shock
Plants in the wild don’t get yanked up and moved very often, so they aren’t exactly adapted for it. Switching your Dumb Cane from one pot to another is always a bit of a shock to their system – even though it’s sometimes necessary.
If you’ve just repotted your Dieffenbachia, it’s likely to droop and pout for a few days. Even after it recovers, you won’t see any new leaves emerging for at least 3 weeks – and possibly for as long as 2 months. Despite appearances, the plant is actually growing, but only underground: the roots are busy stretching out and settling into their new space.
You can help it out by providing lots of humidity to support healthy root growth. A humidifier is usually the best way to do this, though you can also help by grouping your Dumb Cane with other tropical plants or setting it on a pebble tray. If your plant is seriously struggling, you can pop a clear plastic bag over its foliage to create a makeshift greenhouse.
Take great care not to overwater your Dieffenbachia while its roots are in this vulnerable state of transition.
#6: Your Plant Needs to Take its Vitamins
Sunlight and water aren’t the only elements of a healthy Dieffenbachia diet. It needs more than a dozen specific nutrients to build new cells and grow bigger. Commercial potting soils usually have these vital elements mixed in, but if your Dumb Cane has been in the same pot for at least a year without getting more fertilizer, it’s probably running low.
Nutrient deficiency often makes the leaves yellow, brown, small, or deformed. It will take a while for your Dieffenbachia to die from being under-fertilized, but it won’t look right until it’s eating healthy again.
Give your plant some liquid fertilizer to correct the shortfall. To be safe, you should start by applying it once a month at a half-strength dose. You can always up the concentration later, but if you provide more than your Dumb Cane can handle, you could cause lasting damage to the roots. Don’t fertilize in the fall or winter; your Dieffenbachia can’t grow much during this time anyway.
A monthly soil flush with distilled water can also reduce the risk of fertilizer burn. Pour distilled water slowly into the pot and let it trickle from the bottom until 4-5 times the total volume of the container has passed through the soil.
Now that you understand what your Dieffenbachia needs to produce new growth, you should be able to pinpoint what it’s lacking. Check for common problems like under-lighting or overwatering before moving on to rarer issues like nutrient deficiency. We wish you the best of luck in getting your Dumb Cane growing once again!