Plumeria flowers are most fragrant at night in order to lure sphinx moths to pollinate them. The flowers have no nectar, and simply dupe their pollinators. The moths inadvertently pollinate them by transferring pollen from flower to flower in their fruitless search for nectar. Note: While picking some flowers from this tree, the tree fell on me causing well over $41,000.00 in hospital bills (see pic: "whoops part deux"). Be careful when you try to stop and smell some flowers.