A Christmas cactus will rebloom in Arizona when it gets 6 to 8 weeks of long, dark nights and cooler temperatures from September into November, along with less water during that stretch. Without those cues, it stays green and rarely flowers.
Key takeaways
- Buds form when nights run 12 to 14 hours long and temperatures fall to roughly 50 to 60°F.
- Start the routine in mid-September, and expect visible buds about 4 to 6 weeks later.
- Water less from September until buds show, then keep the soil evenly moist through bloom.
- Do not move the plant or set it near a vent once buds appear, since sudden change is a common cause of bud drop.
- Keep it out of direct sun, and bring it inside when the forecast shows a low near 40°F.
Why does my Christmas cactus stay green in an Arizona house?
It stays green because nothing in the house tells it to flower. A Christmas cactus (Schlumbergera) is a forest plant from the mountains of southeastern Brazil, and it sets buds when autumn nights grow longer and cooler. Indoor life has no autumn. A thermostat held at 72 to 78°F and lamps that stay on until bedtime send the same message every night of the year.
Other habits get in the way too. A pot much larger than the root ball pushes leafy growth, and the plant blooms more readily when its roots are slightly crowded. Heavy nitrogen feeding in fall also favors leaves over buds. If you are shopping for a plant, our houseplant department includes holiday cacti among the varieties we commonly carry, though availability changes week to week and season to season.
What triggers a Christmas cactus to set buds?
Two signals work together: 12 to 14 hours of uninterrupted darkness each night, and night temperatures between roughly 50 and 60°F. Cool temperatures carry most of the weight, and a plant held near 50 to 55°F can set buds even under longer days. Above 70°F at night, the plant depends much more on strict darkness.
Light leaks matter. A porch light, a street light or a lamp in the same room can interrupt the dark period, and an hour or two of light on many nights can delay budding for weeks. Fall nights in the East Valley cool into the 60s by early October and the 50s by November, so a shaded patio supplies part of the signal, but warm nights in late September mean you still need to control the light yourself.
When should I start the rebloom routine?
Start in early to mid-September for flowers around Christmas. Buds usually show 4 to 6 weeks after the routine begins, and they need a few more weeks to open. A Thanksgiving cactus follows the same pattern and blooms a few weeks earlier.
| Period | What to do | Watering |
|---|---|---|
| February to August | Grow in bright, indirect light and feed monthly at half strength | When the top inch is dry |
| Early September | Stop feeding and choose a dark spot for nights | Begin stretching the interval |
| Mid-September to October | Give 12 to 14 hours of darkness every night | Top 1 to 2 inches dry between waterings |
| Early November | Look for buds at the segment tips and leave the plant in one place | Resume steady watering |
| December to January | Bloom, away from vents and drafts | Evenly moist, never soggy |
| Late January to February | Prune lightly after flowers fade and resume feeding | Top inch dry |
Our gardening calendars show what else belongs on the schedule each month, which helps you fit the cactus routine around fall planting.
What do I need before I start?
You need very little: bright, indirect light, a place that stays dark at night, and a pot that drains. A covered north or east patio, a spare bedroom or a closet all work.
- A pot only 1 to 2 inches wider than the root ball, with drainage holes. Terra cotta breathes and dries faster than plastic, and you can browse pottery and planters for sizes that suit a small plant.
- A loose, well-draining mix of potting soil with perlite or fine bark. Standard cactus mix drains too fast for a forest plant like this one.
- A balanced, water-soluble fertilizer to use at half strength.
- A cardboard box or dark cloth if you have no room that stays dark.
How do I get a Christmas cactus to set buds?
Give it long, dark nights, cool air and drier soil for about 6 to 8 weeks. The steps below follow the calendar for the East Valley.
- Early September: Stop fertilizing. Leave repotting until after bloom unless the roots circle the pot tightly, and then go up only one size.
- Mid-September: Keep the plant in a bright room indoors, out of direct sun. Move it to a covered, shaded patio once daytime highs fall below about 90°F, usually in October, because direct heat can scorch the segments and bake the roots.
- Every night: Give 12 to 14 hours of darkness, for example from 6 PM to 7 or 8 AM. Place a box or dark cloth over the plant, or leave it in a room where no lights come on. Return it to bright, indirect light each morning.
- Water less: Let the top 1 to 2 inches of soil dry between waterings. A slightly droopy plant is fine, but a fully wilted one is too dry.
- Late October to early November: Check weekly for tiny buds at the segment tips. They look like small pink or red nubs.
- Once buds appear: Stop the dark routine. Set the plant in a stable spot with bright, indirect light and resume steady watering. Bring it inside whenever a low near 40°F is forecast.
- After flowering: Twist off one or two segments from long stems to encourage branching, then resume feeding when new growth begins in late winter.
How should I water and feed it through the year?
Water when the top inch of soil is dry in spring and summer, let it dry a little deeper in fall, and keep the soil evenly moist during bloom. Indoors, that often works out to every 5 to 10 days, depending on pot, light and room temperature. Check the soil with a finger rather than following a fixed schedule.
Feed with a balanced water-soluble fertilizer at half strength about once a month from February through August. Pause from September until flowering finishes.
Hard water leaves mineral salts behind. Our tap water is hard and alkaline, so a white crust can build up on the soil surface or around the pot rim. Once a month, run plain water through the pot until it drains freely from the bottom, and empty the saucer afterward. Rainwater collected during the monsoon is softer if you have a bucket outside.
Why do Christmas cactus buds drop?
Buds drop after a sudden change, such as a move to a new spot, a blast from a heating or cooling vent, a cold draft or a swing between soaked and dry soil. The plant gives up buds it cannot support.
- Moving the plant: Once buds show, pick a spot and leave it there until flowering is over.
- Vents and drafts: Keep the pot several feet from air conditioning and heating vents and from doors that open to outdoor air.
- Dry air: Indoor humidity in our homes can fall to 15 to 25% in spring. A tray of pebbles and water under the pot raises humidity nearby, and you should keep water off the buds themselves.
- Cold: Segments can be damaged near freezing, so bring the plant inside before a frost.
Late-summer heat in a pot without shade causes a different problem, a slow decline in the roots that shows up as limp, wrinkled segments.
Frequently asked questions
How can I tell a Christmas cactus from a Thanksgiving cactus?
Check the segment edges. Thanksgiving cactus (Schlumbergera truncata) has pointed, tooth-like projections on each segment, while true Christmas cactus (Schlumbergera x buckleyi) has smoother, scalloped edges. Most holiday cacti sold in stores are Thanksgiving types, which bloom a few weeks earlier. If yours peaks in November, that is the likely reason.
Why did mine bloom once and never again?
It probably bloomed because a grower had already triggered it before you bought it. After that, the plant needs its own cool, dark nights each fall, and a house kept at one temperature with evening lighting never provides them. Start the routine in mid-September, and expect fuller blooms as the plant matures over several seasons.
Can it live outside in the East Valley year-round?
Not reliably. A bright, shaded patio works from roughly March through November, but summer highs above 110°F can scorch segments and overheat roots in a pot, and winter frost can damage or kill the plant. Keep it in bright shade off hot pavement, and move it indoors for the hottest weeks and the coldest nights.
When should I repot it?
Repot after flowering, in late winter or spring, and only when roots fill the pot or push out of the drainage holes. Move up one size, about 1 to 2 inches wider, with fresh, well-draining mix. A pot that is too large encourages leaves instead of flowers, and repotting in fall can disrupt budding.
How long do the flowers last?
Each flower lasts roughly a week, and a well-budded plant can stay in bloom for about 4 to 6 weeks. Steady watering, a stable spot and slightly cooler room temperatures in the 60s help the show last longer. Heat vents and dry air shorten it.
Is a Christmas cactus worth the effort of reblooming?
Yes, if you have a shaded spot and can spend about two months adjusting light and water each fall. The routine costs almost nothing, and a healthy plant can live for many years. Skip it if your only space is a bright south or west window, or a room where lights stay on late, because buds will be unreliable there. If you would like help choosing a plant or a pot, stop by the nursery in Queen Creek.
