With its distinct red, green, and white coloring, and its propensity for appearing in Christmas floral displays, the poinsettia is a unique and iconic perennial plant, popular all over the world.
While they are generally best suited for indoor gardening, poinsettias can also thrive in outdoor garden settings if growing conditions are favorable and some general precautions are adhered to.
They are native to Mexico and are classified as tropical plants, and therefore prefer warmer conditions.
Poinsettias are not particularly difficult plants to look after, but I find it’s good to know what temperatures they can endure, as this will keep them looking lovely for longer over the cold festive season as well as for the rest of the year.
How cold can poinsettias survive?
Poinsettias perform best in regulated daytime temperatures of 65 to 75 degrees Fahrenheit (18-24 degrees Celsius). They prefer slightly colder climes at night, between 60 and 56 degrees Fahrenheit. At temperatures below 50 degrees Fahrenheit (10 degrees Celsius), their leaves start to drop. Sustained exposure will kill their root systems.
Temperature preference of poinsettias
Poinsettias perform best in regulated daytime temperatures of between 65 and 75 degrees Fahrenheit (18 to 24 degrees Celsius).
But, these pretty blooms prefer slightly colder climes during the night, between 60-65 degrees Fahrenheit (16-18 degrees Celsius).
If you do decide to move or grow your poinsettias outdoors, be mindful that they can be greatly damaged by frost.
Below 50 degree Fahrenheit mark (10 degrees Celsius), their leaves may start to drop. Sustained exposure to this kind of cold will kill their root systems completely.
To give your poinsettias a fighting chance, it is better to keep them indoors where temperatures can be regulated, and only move them outdoors when the weather warms up.
I recommend waiting until the threat of frost has ceased, and ambient temperatures are above 65 degrees Fahrenheit (16 degrees Celsius) during the day and no lower than 50 degrees Fahrenheit at night (10 degrees Celsius).
How to care for indoor poinsettias
There are a few things that I look for when purchasing poinsettias, and a few precautionary care measures that I practice when I bring them home.
Firstly, I always ensure that I select a healthy plant, with vigorous leaf growth all the way down to its base.
Ideally, the large colorful blooms (which are in fact bracts, not flowers) should not be broken or damaged, and the small yellow buds at the center of the bracts should be tight and intact.
Poinsettias hate drafts, and for this reason, are often sold in a protective wrapping of cellophane or paper.
This is a vital part of protecting them from cold and wind damage, which can cause premature leaf dropping and harm an otherwise healthy plant.
At home, I always look for a bright spot in indirect sunlight, preferably close to a window, but take care not to let them touch freezing glass and keep them far away from drafts.
In fact, any fluctuating temperature can be harmful, so fireplaces, heaters, and fans should also be avoided.
Roughly six hours of sunlight a day is a good measure of their needs.
Interestingly, a poinsettia’s rich color blooms most successfully with adequate access to darkness, which it requires for at least 14 hours per night.
This simulates its natural growing conditions of short days and long nights.
Finally, and once the above measures are in place, I regularly check their soil to make sure it is neither too dry nor too soggy, which can cause root rot.
How to care for outdoor poinsettias
Outdoor poinsettias can reach sizes of up to 10 feet (3 meters), as opposed to their much smaller indoor counterparts, and with sufficient care, they will grow quite successfully.
However, great caution should be practiced when moving them outside as they are very susceptible to frost damage.
In temperate areas, May, June, and July are good times for relocation, but only once all threat of frost has passed, and the plant has entered a dormant phase.
Whether you choose to keep them in their pots or plant them in the ground, a layer of good quality mulch can also help to keep them safe in the event of unseasonably cold evenings.
I always check their soil to ensure I am not suffocating their roots.
In addition to this, I tend to pinch back new tips in the hotter days of summer, effectively promoting greater growth.
Fertilizing poinsettias is never a bad idea, but this should be regulated via larger doses in the spring, which are tapered off at the beginning of fall.
How to protect poinsettias from frost
Unfortunately, there is no way to protect poinsettias from frost.
They do not fare well in the cold, and temperatures below their tolerance level of 50 degrees Fahrenheit (10 degrees Celsius) will cause them significant harm and more than likely kill them.
My best advice is to immediately move them indoors when the cold weather arrives and keep them safe until the warmer days return.
Frequently Asked Questions About How Cold Can Poinsettias Survive
Can a poinsettia recover from cold damage?
This depends a lot on how severe the damage is. If it is mild, a poinsettia can be revived with a lot of tender love and care. Move it inside where temperature can be regulated, trim off damaged leaves, and make sure it has the correct measure of indirect sunlight (6 hours per day) and darkness (14 hours per day). Most importantly, make sure you regulate the temperature indoors. Keep its soil moist, but don’t drown it. A houseplant fertilizer in small doses may provide it with an energy boost too.
Should I cover my poinsettias?
These are extremely light-sensitive plants, so yes, it is a good idea to cover them if the goal is to make sure they receive sufficient darkness. Indoor plants can be placed in dark spaces or covered with boxes. Potted outdoor poinsettias can be covered with a row cover or burlap.
The beautiful poinsettia, or Christmas Star, is an infinitely rewarding indoor plant that can continue to bloom year after year with a little bit of regulation and attention.
The move from indoors to outdoors may seem daunting, but I find that once the cycle is complete, it is quite easy to aid them on their journey to reblooming.
Knowing their exact temperature tolerance, I am easily able to provide them with the structured growing environment they need.
Marcel runs the place around here. He has a deep passion for houseplants & gardening and is constantly on the lookout for yet another special plant to add to his arsenal of houseplants, succulents & cacti.
Marcel is also the founder of Iseli International Commerce, a sole proprietorship company that publishes a variety of websites and online magazines.