It prefers a good, deep watering every three or four weeks to frequent shallow waterings. Give a bougainvillea too much water and it can get fungal diseases and root rot. Bougainvillea blooms better when kept on the dry side. Too much water will give you lots of green growth and fewer flowers.
To ensure abundant flowering plants and good overall health of plants, use a balanced, slow-release fertilizer containing nitrogen, phosphorus, and potassium (N-P-K) in equal ratios, such as 5-5-5 or 10-10-10, and don't forget this when repotting.
Plant one in a shady spot and you won't get the riot of blooms — the whole point of planting bougainvillea. You'll get vines and thorns. It needs at least six hours of sun per day.
Bougainvillea is a relatively hardy plant, able to withstand a range of temperatures, from tropical highs of 80 degrees Fahrenheit and above, all the way down to 40 degrees Fahrenheit. That being said, for your bougainvillea to truly thrive indoors, maintain temperatures around 60 to 70 degrees Fahrenheit.
The best time to repot is in late autumn or early springtime. During these times, your plant will be dormant. In the springtime, be sure to transplant your Bougainvillea before the leaves appear. After leaves begin forming, it's best to wait until autumn to do repotting.