How to Keep a Poinsettia Alive Through Christmas. Nothing is worse than buying a $30 poinsettia only to have it drop most of its leaves and wilt before Christmas Day. Luckily, keeping a poinsettia fresh throughout the holidays is easy. All you need to do is learn how to spot a healthy poinsettia at the store and then care for it well once you bring it home.
Don't buy any plants with bare lower stems, wilting leaves or soaked soil, which are all signs of root rot. Poinsettias usually come in foil-wrapped pots and these shiny wrappers hide a lot of sins. Before you buy a plant, pull the pot out of its foil wrapping and examine it. Higher-quality plants are typically not wrapped in foil for display.
Choose plants with dark green foliage that extends all the way down each stem. Brightly colored poinsettia "flowers" are actually modified leaves called bracts. Look for plants with fully colored bracts. Examine the true flowers--the yellow blooms at the base of the bracts. Look for slightly green or red tipped true flowers, as this indicates a fresh plant that will last longer. Avoid plants with pollen-filled, fully yellow true flowers.
Wrap your entire plant in plastic before you go outside if the air outside is less than 50 degrees. Try to park close to the door to minimize the time your picky poinsettia spends out in the elements. Poinsettias are native to Mexico and they don't appreciate being subjected to cold, wind, snow or rain on the trip from the store to your car.
Unwrap your poinsettia and take it out of its foil wrapper. Put it in a decorative container to disguise the ugly plastic pot. Place the plant near a south- or west-facing window where it gets at least six hours of indirect sun per day. Don't let the plant touch the window, as the cold glass will damage the tender leaves and bracts.
Turn your thermostat down to the low 60s at night to extend your poinsettia's life. They like their daytime temperatures nice and warm (about 70 degrees) and cooler nights.
Keep the soil slightly dry. Monitor soil moisture by sticking your finger into the soil every couple of days. Water when the soil is dry down to your first knuckle. Pull the plant out of any decorative containers when you water. Don't let poinsettias sit in a saucer of water. If you can't resist keeping the shiny foil wrapper on, then definitely poke holes in the foil to allow water to drain out.