Answer: You didn't provide any information on the care and feeding your bougainvillea is receiving so it is difficult to pinpoint an exact cause of the browing leaves. Cold weather can cause leaf browning, as can hot winds. Over fertilization, over or underwatering can do the same. I would prune off the damage then carefully water as needed. Withhold fertilizer, too, just in case. Best wishes with your bougainvillea!
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