How to Keep a Poinsettia Alive Through a Toronto Winter

Most poinsettias in the GTA are killed twice: once in a December parking lot, and once by the foil sleeve they came home in. A poinsettia is a tropical shrub from Mexico, damaged at 10 °C (50 °F), a temperature Toronto's average daily high stays below from November through March. Wrap it for the walk to the car, keep it at 18–21 °C away from heat vents and cold glass, take it out of the foil before watering, and it will hold its colour through the holidays and into late winter.

The trip home is the most dangerous part

Every horticultural source gives the same number. Julie Weisenhorn, the University of Minnesota Extension educator in horticulture who writes its poinsettia guide: "Poinsettias will suffer damage if they are exposed to temperatures below 50 degrees Fahrenheit." The Toronto Master Gardeners put it in Celsius: below 10 °C is detrimental.

Compare that to a GTA December. Environment Canada's 1991–2020 normals:

The average December high at Pearson is 1.9 °C, and November's is 7.9 °C. Chilling injury is not an unlucky-cold-snap risk here; it is the default condition of every day you are likely to buy the plant.

Landscape Ontario, the provincial horticultural trades association, describes the outcome: "Never expose the plant to cold temperature for more than a few minutes; a chilled or frozen plant will drop leaves very quickly."

So: ask for a sleeve, buy the plant last, and treat the drive as the hazard. Rosie Lerner, who writes Purdue Extension's Indiana Yard and Garden, is specific about it: "Get the plant from the store to your car as quickly as possible. Preheat the car beforehand to prevent further chilling injury. Plants left in an unheated car can be injured or killed quickly, so drop the plants off at home before running other errands." Then take the wrapping off the moment you are inside. The sleeve that protects the plant for ten minutes yellows it if it stays on.

Some of the damage happens before you get there

A poinsettia can arrive at the till already chilled, and it shows. Tina Smith of UMass Extension and Leanne Pundt of UConn Extension, who write the retail handling notes garden-centre staff work from: "Red varieties of poinsettias with chilling damage have bracts with bluing or necrotic edges with inner bracts that sometimes turn a whitish color." And it accumulates: "The longer that plants are exposed to low temperatures, the more damage that occurs."

Time on the shelf does the rest. Melhem Sawaya, the Simcoe, Ontario consultant behind Focus Greenhouse Management and the Sawaya Garden Trials, has long argued for small, frequent deliveries rather than one big drop. When stock backs up, he wrote in Greenhouse Canada, shelves fill with "plants receiving little maintenance for seven to 12 days, by which time they are almost dead but still occupying precious selling space." So check the outer bracts for a bluish or brown edge, buy from a display that is visibly moving, and do not take the last plant beside a set of automatic doors.

Where to put it in a Toronto house

Temperature: 18–21 °C. Minnesota Extension gives 65–70 °F as ideal. Landscape Ontario adds that "the bright colour of the bracts will remain longer if temperatures do not exceed 22 °C." The Toronto Master Gardeners' home target is 20–22 °C by day, 16–18 °C at night.

Keep it out of the airflow. Minnesota Extension: "Avoid placing poinsettias where the temperature fluctuates or may be drying, such as near cold drafts, heat ducts, fireplaces, fans, space heaters." In a forced-air house that rules out the floor in front of a register, and the spot beside the front door, where every delivery brings in −5 °C air.

Do not let the leaves touch the glass. Lerner: "Make the most of the situation by placing your plant near a sunny window, but do not allow the foliage or flowers to contact cold window glass." A bright windowsill is right; a leaf against the pane on a −15 °C night is a cold burn. Pull the pot back 10–15 cm, and keep it on the room side of a closed curtain.

Light and humidity. Use a south, east or west window. Lerner points out what you are competing with: the plant was raised in a greenhouse at 65–75 °F "with high relative humidity and high light intensity", so "artificial light may be needed for extended growing periods." Health Canada tells households to hold relative humidity between 30 and 50 per cent, which is a mould-prevention ceiling rather than a target for the plant; if your house runs dry, "grouping plants together on a pebble tray will help raise humidity around the plants themselves."

Watering: the foil sleeve is what kills them

This failure is purely mechanical: the decorative foil has no drainage holes, so the water that runs through the pot stays there and the roots sit in it.

Minnesota Extension is unambiguous: "Remove from decorative foil or outer pot before watering… Never allow poinsettia pots to sit in excess water. Constant wetness will rot plant roots." Lerner gives the mechanism: "Watering too often will prevent proper aeration of the soil, and roots will begin to decay." The Ontario agriculture ministry's ONfloriculture lists the same Pythium, Phytophthora and Rhizoctonia root rots on the grower side.

There is also a droop that has nothing to do with water. Smith and Pundt: "Poinsettias left in the sleeve are prone to epinasty (droopy). Epinasty is caused by ethylene production and petioles of poinsettias naturally produce ethylene in response to sleeving." Then the line that matters at home: "Epinasty can be mistaken for wilted plants (due to lack of water)." A plant that travelled sleeved and looks limp may be reacting to the sleeve, not asking for water; they say it recovers in a couple of days in bright light at "65F to 75F", about 18–24 °C. Feel the soil first: watering a plant that is not thirsty is how the foil finishes the job.

• Check by weight or touch. Water when the surface feels dry to a light touch, or the pot feels light when lifted. Never let it wilt.
• Water it in the sink, out of the foil, until it runs from the drainage holes, then let it drain. Or, as Purdue puts it: "If your pot was wrapped in foil, be sure to poke a few holes through the bottom to allow excess water to drain away."
• Empty the saucer. Landscape Ontario: "Discard any excess water which remains in the saucer after 10 minutes."
• Do not fertilise over the holidays. Minnesota Extension says to start only when new growth appears, at half strength.

Poinsettias, pets and kids: what is actually true

Poinsettias are not deadly, and the belief that they are traces to one unconfirmed death of a two-year-old in Hawaii in 1919. Zabrina N. Evens and Samuel J. Stellpflug, both MDs at Regions Hospital Toxicology Education and Clinical Services in St. Paul, set out the evidence in a 2012 review in the Western Journal of Emergency Medicine: a study by Krenzelok reviewed 22,793 poinsettia exposures reported to poison control centres between 1985 and 1992. No fatalities were observed. Ninety-six per cent of callers were not referred to a healthcare facility, 92.4 per cent developed no toxicity, and 3.4 per cent had only minor effects.

The National Capital Poison Center adds that researchers could not find a poisonous dose at all, "even after reaching experimental doses of about 1.25 pounds (500-600 leaves)", and sums it up: "Poinsettia can be irritating but it is not fatal if eaten. If children and pets eat it, they can develop mouth irritation and stomach upset. The sap can cause a skin rash, too."

For pets, read the label rather than the headline. The ASPCA does list poinsettia as toxic to dogs, cats and horses, but the toxic principle is "irritant sap" and the clinical signs read "Irritating to the mouth and stomach, sometimes causing vomiting, but generally over-rated in toxicity." Pet Poison Helpline calls it "only mildly toxic." Put it out of reach anyway, as Landscape Ontario advises for all houseplants, but a nibbled leaf is not an emergency.

If something is swallowed, the Ontario Poison Centre, run by SickKids, answers 24 hours a day in any language at 1-800-268-9017. For animals, call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435 (a fee may apply).

Is it worth trying to rebloom it next year?

Honestly, for almost everyone in the GTA: no. The Toronto Master Gardeners do not sugar-coat what it takes: "It is not at all an easy task; as it requires careful exclusion of light from the plant for some time while maintaining the plant's health."

Landscape Ontario's schedule shows why: cut the stems back to about 20 cm in April; repot and start 20-20-20 fertiliser on June 1; move it outside only once temperatures stay above 10 °C; bring it in in late August, cutting each shoot back to three or four leaves; then from September 20 to December 1, light only from 8 a.m. to 5 p.m. and complete darkness from 5 p.m. to 8 a.m.

Two things make that hard here. The outdoor window is short: on Pearson's normals, the average overnight low only clears 10 °C from June through September, so a plant moved out on the May long weekend spends average nights below its damage threshold. The dark period has to be absolute: the Toronto Master Gardeners specify 14–16 hours of uninterrupted darkness daily for 8–10 weeks, 8–10 hours of bright indirect light, nights at 16–18 °C, and a lower-nitrogen feed during bract initiation. Their warning decides it: "Even tiny light leaks or warm nights can stop bract coloration." A hall light under a closet door is enough.

The professionals doing it properly are next door: Statistics Canada puts 64.9 per cent of Canada's total greenhouse area in Ontario in 2025, the year Canadian growers produced 269.1 million potted plants. Ten months of blackout scheduling is their job. The sensible path at home is to keep the plant as green foliage. Both Minnesota Extension and the Toronto Master Gardeners note poinsettias make good year-round houseplants once you stop chasing the red.