Questions on: Bouganvillea
Ron Smith, Horticulturist, NDSU Extension Service
Q: I have a bougainvillea that is flowering nicely, but the lower stems are losing leaves and tend to be scrawny and woody. I see new shoots at the top of these stems, which are blooming well. The plant is in full sun, potted in the original pot and gets watered about every third day (dependent on how dry the soil is). I use a bloom feed once a week as recommended by the nursery. (e-mail reference)
A: You may have scale insects on the stems. Look closely for small lumps (may be the color of bark) on the stems. If present, re-contact you local nursery for control chemicals.
Also, what can you tell me about butterfly bushes? Do I always cut them back in the fall? How far back do I cut them and if I didn't cut them back in the fall, and I should have, can I cut them back in the spring? They are about 2 feet tall now.
And finally, one more question. My white butterfly bush grows bigger than my dark purple one. Is this normally true or could it be that one gets more sun? (Middleport, N.Y., e-mail)
A: The "flower" is actually a bract, which is a modified leaf. The true flower is insignificant and atrophies quickly after opening. The fact that the plant is dropping bracts quickly is an indication of variation in watering. Generally, the bougainvillea prefer dry soil when blooming. Allow the plant to dry out between waterings. They need as much sun as one can provide, and just enough water and fertilizer to keep them alive--not an abundance of either one. Condition the plant to moving outside by setting it out in the sun just for a half hour the first day, 40 minutes the second day, 50 minutes the third and so on. It could be that you have a thornless form (labeled "inermis" on the tag), which is great because those thorns can give a vicious scratch.
As for the butterfly bush--Buddleia davidii--cut it back in the spring before new growth begins, as short as you would like. It flowers on new growth, so if you cut the spent flowers back, it will continue to flower all summer.
The difference in vigor between your butterfly bushes is not unusual. As a broad generalization, the white flowering forms are more vigorous. If they need anything, it would be lime, about 4 pounds per cubic yard of soil. Or, simply work a cupful in around each plant and water well.
Q: Can you give me some information on how to care for my bougainvillea? (LaMoure, N.D., e-mail)
A: Bougainvilleas are difficult to care for under normal room conditions. They need a sunny windowsill and should be kept cool through the winter. Give it a good pruning at this time, and reduce watering. As spring arrives, increase the watering and heat to stimulate growth and blooming. If it ever needs repotting, do so in the spring before new growth begins.
Q: Can you tell me why my bouganvillea isn't blooming? I also sent in for some sub-zero hibiscus and the advertisement claims that I can leave it out and it will become a perennial bush. Is this true? (Pipestone, Minn.)
A: Bouganvillea need LOTS of sunshine and warm weather. They will bloom someday--it just requires patience. I wish I could tell you when that will happen, but I can't.
Concerning the sub-zero hibiscus, it depends on how sub-zero they are talking about! I would believe them, up to a point! To be on the safe side, I would provide some mulch coverage this fall after freeze-up.
Q: I purchased a red bougainvillea in full bloom. I planted it on the south side of the house in full sun. Now the plant has lost many leaves, and many of those that remain are brown. Please help. (Ft. Lauderdale, Fla., e-mail)
A: It sounds as though you planted the bougainvillea in the right location--the hotter and more sun these plants can get, the better. My guess is that the plant may not have been acclimatized completely to the outdoor environment, or that you got one that had a root rot disease. If you can get your fingers between the woody thorns and scratch the bark, check to see if the cambium is still green beneath the outer bark. If it is, it will likely come back; if it is light green or brown to yellow in color, the plant is history. Take it back to the nursery and get it replaced with a healthy one. My experience with these plants is that they are trouble free and grow pretty much like scrambling weedy vines. The bougainvillea usually needs regular heavy pruning to get it to look its best and produce flowers.
Q: I have a bougainvillea that has been in the same pot for about four years. It grew really well this year, but still no flowers. What do I do with it this winter to get it to flower next year? (Faulkton, S.D.)
A: The same thing you did the past four winters! Just kidding of course, but you can cut it back hard and bring it indoors well ahead of the first frost. Place it in a south-facing window and provide supplemental lighting to give it at least 14 hours of continuous light.
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