This is one of Tiger Lily's favorite plant specimens at this (or any) time of year. The blossoming of Schlumbergera bridesii or Zygocactus is a much anticipated event in many households where their owners have learned to care for them. In other, sad homes, they sometimes don't last the winter. We're including some information here so that you don't join the cohort of Christmas cactus assassins.
The first thing you need to know is that this plant is a succulent native to the South American jungles. Christmas cacti are quite different from other cacti and succulents – they are tropicals, not desert plants. They require more water and don't adapt well to drought conditions. Other differences are their preference for mixed rather than direct sunlight and relatively cooler temperatures. It is therefore best to keep these plants away from heaters, fireplaces, radiators, furnace ducts, and other heat sources. Place the cactus in a sunny location while indoors and if outdoors during the summer, find a place that has a sun/shade mix to prevent the plant from getting burned. Watering this type of cactus is sometimes a problem because folks tend to treat them the same as they would a regular desert cactus. Underwatering in this way will stress the plant if it doesn’t kill it outright. Others make the opposite mistake and overwater, causing the plant to rot at the roots. If your plant came to you as a gift and it is still in a lined basket, replant it immediately in a garden pot with a drainage hole.
The best way to be sure your plant is getting just the right amount of water is to wait until the soil is dry on the top and still a bit moist toward the bottom. Then water the plant until the soil is saturated. Drain off any excess water that accumulates on the bottom. Never leave this plant in standing water or with runoff sitting in the overflow tray. Don’t water again until the top half of the soil feels dry to the touch. Well-drained soil is very important. You should purchase potting soil that is designed specifically for cacti. If you can't find cactus potting soil, you can mix two parts regular potting soil with one part sand.
Wholesale growers usually time these cacti’s blooming cycles to peak just before the holidays. To ensure that your cactus will bloom in time for Christmas, you will need to give the cactus a 3 – 4-month rest period. You will want to cut back on the watering, leaving only the top of the soil moist. Stop watering the plant beginning in October, and then begin watering again (don’t saturate) in November. To stimulate the budding process, relocate the plant so that it is in darkness at night and relatively cool temperatures for at least 14 hours per day. The new location should be totally dark for at least 12 hours – no artificial light. Once the buds form, they can take from 10 to 12 weeks to fully bloom. Also make sure the air has enough humidity so the buds don't dry up and fall off.
After the cactus blossoms out and the blooms fall off, you can prune your cactus so that it bushes out instead of becoming vine-like and unmanageable. You'll also find that the cactus will bloom better the following year. As new growth appears in the spring, put a diluted solution of liquid houseplant fertilizer 2 to 3 weeks after the start of the new growth. The cactus should be repotted every 2 to 3 years depending on how depleted the soil is. Repotting should be done in the spring, but if the plant is at risk of dying because of its potting condition, then repotting can be done anytime of the year as needed.
With the proper care, the annual blooming of the Christmas cactus can be a spectacular event at your home, too.
