The Agent's Observations Jan 1997

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Question: My Christmas Cactus did not bloom this year. What happened?

Answer: There are several "holiday" cacti. They are Christmas Cactus, Schumbergera bridgesii, with smooth leaf margins or edges; Thanksgiving Cactus, S. truncata, which blooms earlier and has saw-tooth leaf margins and two oppositely pointed tips at the end of each leaf; and the Easter Cactus, S. Gaertneri, which blooms naturally in the spring and has smooth leaf margins. These cacti species originated from the Brazilian jungle and grow naturally as epiphytes (in the air) in the branches and bark of trees. (See December 1996 High on the Desert Newsletter for more information.)

These plants are short-day plants like poinsettias. Flowering is initiated by cool temperatures, 45° to 55°F, drier soil, and the naturally shorter days of spring or fall. The Christmas Cactus in question did not bloom because one or more of these conditions were not met.

To induce flowering, determine what type of cactus species you have. Ten weeks before blooms are desired, place the plant in a cool closet or dark cupboard from sun down to sunup, never letting any light reach the plant during seclusion. Keep the soil drier than normal. Once flower buds are set you can cease this practice and increase watering. Source: Houseplants, The American Horticultural Society, 1980, pp.81 and 85.

Question: What should I do to keep my poinsettia blooming and growing throughout the year?

Answer:  Poinsettia, Euphorbia pulcherrima, is a tropical plant that originated in Mexico. Members of the Euphorbia family have white latex sap. Light requirements are bright but not direct sunlight. Dim light or darkness will shorten its life. These plants should be watered when the soil surface feels dry to the touch. If a poinsettia is allowed to wilt its life span will be shortened. Watering should insure that the entire root ball is moistened. Poinsettias should not be allowed to sit in water because their roots are very prone to root rots. Ideal temperature should never exceed 72° F during the day or 65° F at night. Plants do well in high humidity environments. Low humidity and temperatures over 75° F are detrimental to the plants. Beware of placing plants near heat vents, on top of televisions, or in areas that are drafty or have sudden changes from hot to cold. Concentrations of 1/8 to 1/4 of recommended strength houseplant fertilizer applied at each watering will "spoon-feed" the plant and help maintain a healthy plant during the holidays. During the winter months with less sun light and cooler indoor temperatures plant growth will be slowed, therefore the amount of fertilizer should be decreased as well.

After the colorful bracts (we think of them as flowers) fall, place the plant in a cool room and let the soil stay nearly dry until spring. Repot the plant in new soil and cut back the stems to six inches above the pot rim. Then move to a sunny location, water well, and watch for new growth. Increase fertilizer concentration to 1/4 to 1/2 strength and apply at each watering. Pinching back terminal growth encourages branching and more blooms. Poinsettias are short-day plants; meaning that flowering is induced as day lengths shorten. To insure return holiday blooms keep in absolute darkness from sundown to sunup for ten weeks beginning in October. If this is too much work, the old plant can be discarded and a new one purchased for the next holiday season.

Rob Call
January, 1997