~by Richard Jauron, Willy Klein
AMES, Iowa – Poinsettia plants remain one of the most popular holiday flowers. The familiar red flowers have been joined by even flashier colors to include pastel yellow and vibrant bi-colors. Because poinsettias have been forced into bloom, they need some extra care to keep them healthy and looking good throughout the holidays. Horticulturists with Iowa State University answer several questions related to watering poinsettias. To have additional questions answered, contact the ISU Hortline at 515-83-3108 or hortline@iastate.edu.
Why is my poinsettia dropping some of its leaves?
Leaf drop is likely due to some type of environmental stress. Improper watering is the most common reason for leaf drop on poinsettias in the home. Over-watering will cause the lower leaves to turn yellow and drop. Plants that are allowed to get too dry will wilt and also drop leaves.
The water needs of a poinsettia can be determined with your finger. Check the potting soil daily. When the soil surface becomes dry to the touch, water the plant until water begins to flow out the bottom of the pot. The pots of most poinsettias are set inside decorative pot covers. When watering these plants, carefully remove the poinsettia from the pot covering, water the plant in the sink, then drop the poinsettia back into its pot cover.
Also, make sure the poinsettia is not located near a heat source or cold draft. Warm, dry air blowing across the plant from a furnace register or rapid temperature fluctuations (such as near a door) can also cause leaf drop.
My poinsettia suddenly wilted and died. Why?
The sudden death of the poinsettia was likely due to a root rot. Pythium and Rhizoctonia root rots typically occur when plants are watered too frequently and the potting soil is kept saturated. Allow the surface of the potting soil to dry to the touch before watering poinsettias. Also, don’t allow the pots of poinsettias to sit in water. Discard excess water that drains into pot coverings or saucers.
Small, white insects flutter about my poinsettia when I water the plant. What are they and how do I control them?
The small, white insects are likely whiteflies. Whiteflies are common insect pests of poinsettia, hibiscus, chrysanthemum and a number of other indoor plants. They are most often noticed when watering or handling a plant. When disturbed, whiteflies flutter about the plant for a short time before returning to the plant.
Whitefly adults are small, white, moth-like insects. Female adults lay eggs on the undersides of plant foliage. After five to seven days, the eggs hatch into small, pale green, immature insects called nymphs. The nymphs crawl a short distance before settling down to feed for two to three weeks. After feeding, the nymphs progress to a nonfeeding stage and then finally to the adult stage.
The nymph and adult stages of whiteflies feed by inserting their short, needle-like beaks into foliage and sucking out plant sap. Heavy whitefly infestations may cause stunting or yellowing of leaves, leaf drop and a decline in plant health.
Whiteflies on poinsettias and other indoor plants are extremely difficult to control. Prevention is the best management strategy. When purchasing plants, carefully check for whiteflies and other insects. Avoid purchasing insect-infested plants. Insecticides are not a good control option as they are not very effective. It’s often best to tolerate the presence of a small infestation of whiteflies on a poinsettia and then promptly discard the plant after the holidays
