In spite of the popularity of holiday cacti, many misconceptions about them still remain, notably the difficulty to bring them to full bloom. In actual fact, they are easy to get to flower once you know the secrets.
To learn how to make them bloom, let’s take a trip back to their original home in the mountain forests of Brazil. Unlike most cactus, they don’t grow in sunny, arid sites, but on trees, in moderate shade and relatively high humidity. Like all cacti, though, they remain succulents, storing water in their flattened segments. Although “tropical plants”, they do undergo seasonal change. When shorter days, cool evenings, and drier conditions signal the beginning of the dry season, they begin to bud, then burst into flower with the return of the rains. All you have to do is convince your cacti they are back in a Brazilian forest at the beginning of the dry season.
Three factors are involved: shorter days, cooler temperatures, and drier growing conditions. Provide shorter days, or more precisely, nights of at least 15 hours, for about three weeks. One of the best methods is to put them outside for the summer and only bring them indoors well into the fall so they can benefit from naturally short days. Cooler temperatures are also best provided by placing the plant outdoors in the fall. Night temperatures around 60°F seem to be sufficient to produce buds abundantly. The final factor, drier conditions, seems to compliment the other two. After a spring and summer of watering thoroughly whenever the potting mix felt dry to the touch, let the potting mix dry out more completely between waterings in the fall.
While the buds are swelling and during flowering, increase watering rates so the mix never quite dries out. Then, after the last flowers fade, provide a two-week period of complete dryness. This seems to trigger blooming again and many will provide spectacular blooming during the late winter through early spring season.
Thwarting Bud Drop
Bud drop on holiday cactus has often been attributed to moving the plant at a susceptible period in its growth cycle, the theory being that its flower buds grow toward the light, and if the plant is turned in another direction, the buds come loose as they bend toward a new light source. You may want to take heed of this factor and not give your holiday cacti the typical weekly quarter turn usually given to houseplants.
Spring & Summer Care
Bright light with no direct mid-day sun during the summer months, such as an eastern or western window , is fine. Regular indoor temperatures and humidity also suit them. Water thoroughly and regularly from spring until temperatures drop off in the fall. Feeding should follow watering patterns. Diluted high phosphorous fertilizer can be added to each watering during periods of stem growth and flower bud formation. None should be given when watering is decreased.
Holiday cacti can usually be left in the same pots for several years at a time unless your water is hard, in which case annual repotting is wise. They are intolerant of growing mixes rich in mineral salts. Repotting is best done after the last blooming period. Just change the potting mix; it is not necessary to repot into a larger pot since holiday cacti bloom most abundantly when root-bound.
To reproduce holiday cacti, simply break off a section with two or three segments and let dry for few days before inserting into a roothing mix kept lightly moist. They root best in spring or early summer.