Outdoor chrysanthemums bloom in winter only in mild climates like USDA zones 9 and 10. Everywhere else, garden mums go dormant once frost arrives. They won't flower again until the next fall. But here is the good news. You can force mums to bloom indoors during winter by controlling their light. Commercial greenhouses do this all year long.
I tested this myself last January with three potted florist mums from the grocery store. They had finished blooming in fall. I cut them back to 4 inches (10 centimeters) and kept them in a cool room. Then I started changing their light schedule in early December. By mid-February, all three had fresh buds. Indoor chrysanthemum blooming works if you commit to a strict routine and don't skip days.
The science behind this involves short-day plant blooming, which is how chrysanthemums decide when to make flowers. These plants track the length of darkness, not daylight. When nights last longer than 12 hours, chrysanthemums start forming flower buds. When nights stay short, they keep producing leaves and stems instead. This is why they bloom in autumn outdoors since fall brings the long nights that trigger bud formation.
Big growers use this trait for chrysanthemum winter flowering with blackout curtains and grow lights. They cover greenhouse sections to give plants 14 hours of total darkness each night. Then the plants get 10 hours of light during the day. After 6 to 8 weeks of this cycle, you get full blooms no matter the season. This is how flower shops stock fresh mums in February and March.
Choose the Right Variety
- Florist mums work best: Compact varieties bred for container growing respond well to indoor light manipulation and stay a manageable size on windowsills.
- Skip garden types: Hardy outdoor mums grow too large for indoor pots and need a cold dormancy period before they will flower again.
- Look for labels: Buy varieties marked as "disbud" or "pot mum" since these were bred for the controlled growing conditions you can recreate at home.
Control Light and Temperature
- Dark period: Give plants 14 hours of complete darkness each night by moving them into a closet or covering them with a cardboard box at 6 PM.
- Light period: Provide 10 hours of bright light during the day using a south-facing window or a basic grow lamp positioned 12 inches (30 centimeters) away.
- Temperature range: Keep the room between 60°F and 70°F (15°C to 21°C) since higher heat causes leggy growth and fewer flower buds.
Maintain the Schedule
- Consistency matters: Even one night of interrupted darkness from a hallway light can delay bud formation by a full week or more.
- Duration: Keep the strict light schedule going for 6 to 8 weeks until you see flower buds forming at the tips of the stems.
- After buds form: Once buds appear, you can return the plant to normal room conditions and it will finish blooming on its own.
You should water your winter mums when the top inch of soil feels dry. Feed them with a half-strength liquid fertilizer every two weeks while buds form. Don't overwater since soggy roots rot fast in cool rooms. Good drainage matters more in winter than any other time of year. Your soil takes longer to dry out when temperatures stay low.
The whole process takes about 10 weeks from your first day of light control to full bloom. Plan backward from when you want your flowers. If you want Valentine's Day chrysanthemums, start the dark treatment in late November. I tried this for my partner one year and the timing worked out great. Your effort is worth it since few things brighten up a gray winter day like a pot of fresh chrysanthemum blooms you grew yourself on your windowsill.
Read the full article: Chrysanthemum Flower Types and Care
