There are many reasons why poinsettias start to lose leaves. Photo: .gardeningwithsurgicalprecision.com
I’ve received several emails recently from gardeners struggling with poinsettias (Euphorbia pulcherrima) whose lower leaves turned yellow and dropped off, often within days of purchase. Yet the poinsettia, while not necessarily the easiest houseplant of all, has the reputation of being able to “get by” for at least a month or two if given reasonable care. Why then is yours losing its leaves so soon after you bought it?
A Symptom of Stress
Leaf drop in the poinsettia is a symptom of stress. The plant is not happy and shows its displeasure by dropping leaves. Usually, it’s the lower leaves that are sacrificed first. They turn yellow and off they fall. Then, if the cause of stress isn’t corrected, the leaf drop will gradually progress up the plant until it appears nearly naked, with only the colored bracts and a few green leaves on the top.
So much for the symptoms, but what causes this stress? Here are 10 possibilities, starting with the main cause of leaf drop.
Most Likely Cause of Leaf Drop: Underwatering
This cause is so common that poinsettias really should come with a blinking warning label: “This plant needs regular watering!”, because so many people don’t water theirs, or at least, not often enough nor abundantly enough.
When you find your poinsettia wilting, with all its the leaves and bracts hanging limply like handkerchiefs drying in the sun, plus its soil is dry to the touch, it’s pretty obvious that it lacked water. Usually, the foliage will recover its turgidity after a thorough watering, but… a few days later, the lower leaves begin to turn yellow and drop off. And a lot of people don’t realize the two are associated.
Be forewarned that a poinsettia in bloom is a thirsty plant. It loses a lot of water to evaporation through its big, colorful bracts and as its owner, it’s your duty to replace it.
I must point out that this leaf loss due to underwatering is not always your fault. The stress may have occurred in the store before you bought the plant, then, when you bring home an apparently healthy poinsettia, leaf drop sets in a few days later. Note that box stores and supermarkets, especially, are not known for their proper maintenance of the plants they sell.
Solution: Water thoroughly any poinsettia whose soil is dry to the touch and whose leaves have wilted. That way, you can at least save it, although some leaf loss (even major leaf loss) is likely.
Once it has recovered, learn how to water your poinsettia properly so it won’t happen again. It’s actually very simple: whenever the soil is dry to the touch, water deeply, enough so that the excess water flows into the saucer.
Now, since your plant has already suffered from dehydration, it will have lost a lot of the fine roots that usually do most of the job of absorbing water. A simple light watering is therefore not likely to be enough. Instead, just to be sure the plant really does get enough water, let the plant soak in the water that drains into the saucer for 15 to 20 minutes, then empty the saucer. That will allow its damaged roots to soak up enough moisture and will help reduce leaf loss.
It’s important to understand that you can’t force a poinsettia to adapt to a specific watering schedule. The typical “I water once a week” method can never be counted on. At some point, you’ll almost always end up under- or overwatering the plant, depending on the conditions.
This is because the same plant may well find a weekly watering quite adequate during an average week indoors, but then can wilt terribly the following week because it’s suddenly sunny and the window ledge became extra hot. And yet a week later, when the weather is exceptionally gray and cool again, the potting mix might still be almost soaking wet a full week after the plant was watered. If watering needs vary so widely, it’s because indoor conditions change constantly.
Ideally you would check the soil every 3 or 4 days – yes, that often! -, pressing your index finger into the soil up to the 2nd joint: if the soil is dry, water well. If it is still wet, come back 3 or 4 days later and check again, watering only when needed. That’s the key to successfully watering almost any plant, not just the poinsettia! You may well find that the same plant can sometimes need watering after only 4 days under some circumstances and, at other times, only after 10 or 12 days.
Mini-poinsettias are very trendy, and also inexpensive, but hard to keep alive. They’re not actually dwarf poinsettia plants, but rather young cuttings of regular ones grown in small pots and forced to flower before their time. That leaves them especially susceptible to underwatering, as their tiny pots hold little soil and dry out quickly. With these delicate dainties, you really need to check the growing mix every two days for signs of dryness. If the soil is dry, water thoroughly; if not, try again two days later. They’re babies and really need a lot of babying!
Or transplant them into a larger pot. That will make a huge difference!
Other Causes of Leaf Loss
So much for the main cause of poinsettia leaf loss, underwatering, but there are others. Read on!
Problem #2: The Plant Was Exposed to Cold
In most of the Northern Hemisphere, Christmas is just about the coldest time of the year, so when you purchase a poinsettia, just bringing it back from the store can stress it severely. Even a few minutes of exposure to temperatures below 10 °C can cause leaves or bracts to fall off.
Solution: Always insist the salesperson carefully bag your poinsettia before you leave the store. And don’t place a poinsettia on a frozen seat in an icy car, but instead heat your car in advance.
Problem #3: It Has Been Kept Wrapped Too Long
Poinsettias give off a toxic gas called ethylene. When they’re in the open, this gas diffuses rapidly and causes no harm. But if you keep your plant inside a closed plant sleeve for a few days, the concentration increases and leaves and bracts will begin to fall.
Solution: Remove the poinsettia from its wrapping as soon as you get home. If you intend to wrap your poinsettia as a gift, do so just before you about to give it, not days ahead.
Problem #4: Carbon Monoxide Exposure
The poinsettia is the canary in the coalmine of houseplants when it comes to carbon monoxide (CO), an odorless, tasteless, toxic gas, reacting well before humans show the slightest symptom. If your plant starts to lose its leaves practically as soon as you bring it into your home, the level of carbon monoxide in your home may be too high.
Solution: Check the level of carbon monoxide in your home using a carbon monoxide alarm. If it goes off, leave your home immediately and call emergency services.
Problem #5: The Air Is Too Dry
Poinsettias tolerate dry air relatively well, especially compared to so many other indoor plants, but there is a limit. When the air is exceptionally dry, remaining at less than 30% almost all the time, the leaves begin to drop off, often browning at the margins or at the tip before they fall. If the soil dries out very quickly after a good watering, say in only 2 or 3 days, that’s another symptom that the air may be very dry.
Solution: Increase the humidity using a humidifier or place the plant on a humidity tray.
Problem #6: The Plant Was Overwatered
It seems illogical, but a poinsettia will react the same way when it’s overwatered as when it’s underwatered: the foliage wilts and drops off. Why? If the potting mix remains overly wet for a long time, the roots begin to rot due to the lack of oxygen and when this happens, the foliage wilts, despite the abundance of water, since there are pretty much no roots to absorb it.
Solution: Saving a poinsettia whose roots have begun to rot isn’t easy, because rot is a disease (Pythium or similar) that spreads from dead or dying roots to living ones. It is probably best to simply replace any poinsettia suffering from rot.
Problem #7: It’s Too Hot or Too Cold in the Room Where You Keep Your Poinsettia.
If you find the room where you keep your poinsettia cold or too hot, it might well agree with you. And, stressed as it now is, will shed a few leaves.
Solution: The ideal temperature for a poinsettia is between 60 and 75˚C (15 and 24˚C). If it is colder or warmer than that, especially over a long period, it’s best to move it to a spot more suitable to its needs
Problem #8: Lack of Light
This problem is usually seen only in the long run, because a poinsettia can usually take 3 or 4 weeks in the shade or partial shade before reacting negatively and starting to lose its lower leaves. That’s why you can use a poinsettia almost anywhere in the home over the holidays, even in a dark corner. But if you want your poinsettia to remain in good condition until spring, it will need good light.
Solution: After Christmas, place your poinsettia in a spot where it will receive adequate lighting, including at least a few hours of sun a day, such as near a sunny window.
Problem #9: Insect Infestation
Whiteflies love poinsettias, piercing the leaves to lap up their sap, thus causing their foliage to slowly turn yellow and then drop off. Spider mites, mealybugs and scale insects are other sap-sucking insects that also sometimes infest poinsettias and give similar results.
Solution: Usually, the plant was already infested in the store, so the first solution is, of course, to carefully inspect the plant before you buy it. Look especially under the leaves and at leaf axils, as that is where pests often hide. Different treatments, including sprays with insecticidal soap, neem oil, horticultural oil and rubbing alcohol can be used to control the invaders. And keep the plant isolated from your other houseplants so the infestation won’t spread.
Problem #10: Aging Leaves
It’s perfectly normal for a poinsettia to lose a leaf or two from time to time. That’s its way of getting rid of older, less functional leaves.
Solution: Just pick up the dead leaves!
Poinsettias Really Aren’t That Difficult
I hope the above list of problems and solutions didn’t scare you off, because, in fact, the majority of people who water their poinsettia correctly have no problem keeping it in good condition for at least a month or two. And those who, in addition, make sure to give it adequate light can even expect it to hold on to its beautiful bracts until May or even June for a full 6 months of beauty!
As for how to get your poinsettia to bloom again, an entirely different subject, here are some tips.
No, the poinsettia isn’t difficult to maintain, but like any plant, it still does require at least a bit of basic care to be happy. Give it what it needs and your poinsettia will repay you in spades!
Text based on an article originally published on December 10, 2015