Ask Mr. Smarty Plants

We can only speculate about what might have happened to your bougainvillea. To us, it seems the most likely cause is transplant shock. While bougainvillea is not a native plant in North America, the principals involved in transplant shock are virtually universal for any plant anywhere.

Transplant shock in the usual sense refers to rapid physiological decline of a plant shortly after being moved from one location to another. The problem is typically initiated by damage to the plant's roots during transplanting which leads to an inability of the root system to take up enough water to supply the demand placed on it by the top parts of the plant. Wilting is the immediate visible result of insufficient water-uptake. Insufficient water in a plants vascular system and consequently within its cells can then lead to serious damage caused by higher concentrations of dissolved salts and minerals.

Even if you didn't un-pot your plant, but merely moved it from a shady location to a sunny one damage could easily occur. Bougainvilleas are extraordinarily tough, drought- and sun-tolerant plants. However, if yours had been growing in a shady location and you suddenly moved it to a full-sun location there in Arizona, it likely suffered from both wilting-related damage and from sun-scorch. Plants that grow in full sun build up a type of natural sunscreen on their leaf surfaces. The same plant growing in shade will not need that sun protection and will not produce it. If the shade-grown plant is suddenly moved to a sunny location, wilting and sun-scorch are usually the first visible signs of a problem. This can, and often does, happen in a single day.

Moving the plant back to the shade was the right thing to do. You should also prune the plant back to remove the damaged tissues. Don't worry, it'll resprout. Do not feed your plant at all until it is showing signs of healthy recovery. Once the plant has recovered a little, begin acclimating it to more sunny growing conditions by moving it to an area where it is getting full sun only part of the day. Morning sun is best. Once it is well-adapted to partial sun, you should be able to then move it to full sun with no problem. Of course, it will need more water in the full-sun location.