Throughout the Americas, plant species have evolved flowers whose principal pollinators are hummingbirds. Such plant families include Bromeliaceae, Gesneriaceae, Heliconiaceae, Loranthaceae, Rubiaceae, and Scrophulariaceae. 

Plant characteristics favored by hummingbirds include: flowers that are bright red and orange-red, which are colors that birds are sensitive to; long floral tubes - with their long slender bills, hummingbirds are perfect for reaching deep for nectar; unscented flowers - hummingbirds have a lack of smell; and plentiful nectar - hummingbirds beat their wings at the rate of 15 to 80 times per second and their heartbeats can reach a rate as high as 1260 beats per minute, resulting in the need for a high calorie diet.

References: Angiosperm pollination syndromes (Vanderbilt University) and Why do our hummingbirds hum? (Arthur C. Gibson, The Mildred E. Mathias Botanical Garden Newsletter, Summer 2000, Vol. 3 (3))