Nectar Producing Plants and Their Relationship to Hummingbirds

Illustration by George West

There is a very old and intimate relationship between hummingbirds and the nectar producing plants that depend upon them for pollination. In North America there are more than 200 native species of nectar producing flowering plants. These particular flowers are pollinated by a variety of bees, butterflies and, to a lesser extent, our nectar eating bats. However, at least 150 species of these flowers are primarily, and in some instances exclusively, pollinated by hummingbirds. This particular group of flowers have physical features that prevent the other pollinators from being successful with these particular nectar yielding flowers.

The other pollinators, to varying degrees depend upon color, smell or aroma, and other physical features of the flowers themselves – such as the shape and depth of the flower, the depth of the nectar inside the tube of the flower, and whether or not there’s a place for them to land on the flower in order to gain access to that plant’s nectar. Hummingbird vision excels in the warmest of the warm ultra violet spectrum of sunlight and this is a primary reason why hummingbirds are particularly attracted to the colors red-orange, light red, dark red and purple. In the case of bees, for example, yellow is the color of flower they lock onto.  This helps in understanding why throughout most of the year, bees are not so well attracted to all-red hummingbird feeders. This is why the vast majority of hummingbird feeders are red and not yellow. Only the cheapest of hummingbird feeders, and the lowest quality overall, feature nectar ports that are colored yellow and that’s the reason why folks who buy these types of feeders (usually from discount and non-specialty stores) complain about bees being a problem.

While other pollinators use smell or aroma to guide them into nectar producing flowers, the flowers that hummers utilize have very weak scents or no smell at all. Color is the feature that attracts hummingbirds best. Also, the flowers they depend upon are generally trumpet shaped, quite deep in physical dimension and the nectar is located deep down at the bottom of the flower and therefore usually inaccessible to the other pollinators. Keep in mind that hummingbirds have quite long beaks in relation to their overall body size and that their tongues are about twice the length of their bills. The types of flowers I have described as hummingbird flowers are what scientists call an “ornithophilous syndrome”, i.e. they are pollinated by hummers.

These plants have a number of adaptations in common. They usually bear big red flowers that are solitary or found in loose clusters at the tips of flexible stalks. The flowers hold their nectar at the base of the stout long tube. Nectar concentrations in any given such flower are miniscule. An average size hummingbird may have to visit between 60-80 flowers to gain the equivalent amount to a single drop. It takes thousands of nectar producing plants to keep a single hummer alive for a single day. And, considering that these nectar producing plants need 24-48 hours to regenerate the next mini amount of nectar, the hummers must have access to many thousands of flowers whose nectar hasn’t already been usurped by another hummer.

The flower petals are thick enough to prevent an accidental puncture by the hummer’s bill or theft of precious nectar by a bird, such as an oriole, or insect that cannot pollinate the plant. Blooms occur only during the daylight hours when the hummers are active and they have little or no scent. The pistils and stamens of the flowers project in such a manner that they are likely to touch the head of the feeding bird. Plants that rely on hummers for pollination eliminate the landing platforms that nectar-slurping competitor bees need for landing. Bird-pollinated flowers tend to have the petals arranged in a radial fashion. Bee-pollinated flowers have a symmetry that is “zygomorphic”, that is bilateral or in some other way not radial. In fact, there are more similarities between the flowers of plants that are pollinated by butterflies and hummingbirds than between the flowers of plants that are pollinated by bees and hummingbirds. (Butterflies, unlike bees, can reach deep down in certain flowers.)

Plants that are pollinated by hummingbirds must spend considerable energy to produce their nectar. The plants have adapted to provide enough nectar in a manner that allows them to present it to the birds. Perennials benefit from having a long-lived pollinator like a bird more than annuals do. Hummers pollinate many epiphytes, like orchids. Hummingbird flowers tend to bloom for a longer period of time than insect-pollinated ones.

Characteristics of Flowers Pollinated by Hummingbirds, Butterflies and Bees

In the western US, there are many species of nectar producing wildflowers that hummers are known to pollinate. In the eastern region, there are considerably fewer. The state that has the most is California with about 80, followed by Arizona with about 50.

In Arizona’s White Mountains, nine species of hummingbird flowers, all similar in color, shape and size, compete for pollination. Most make nectar at similar rates. The effect of the competition is reduced because the anthers and stigmas are oriented differently, resulting in different parts of the bird transporting the pollen of different plants. In fact, the cardinal plant’s (not to be confused with the bird species) flowers of the region produce no nectar at all. They attract hummingbirds to them by mimicking the nectar producing plants in all other respects.

The hummers have done some adapting, too. There is a correlation between the bill length and shape of the bird and the shape and size of the flowers it forages upon. The most striking example of this occurs in the Andean Swordbill and the passionflower that it is dependent upon for nectar. (In our website archive of birding articles, there are video clips examples you can view by clicking on Hummingbird Bills and Tongues). The flower has a remarkably long tube, and the swordbill has the longest bill of any hummingbird. The long bill and extensible tongue of the swordbill allows it to feed on a flower whose nectar is just too far away for any other hummer or insect. Perhaps this is why the Andean Swordbill defends no feeding territory like many of our North American hummers do. With little competition for nectar, it feeds by visiting many plants over a large area. In many cases with other hummers, the length of the flower tube and the length of the hummer’s bill that pollinates it are quite similar.

We know from feeding hummingbirds that they have a definite preference for the color red. This is not an inborn trait, but is learned at an early age. Bees are not attracted to red because their color vision range barely reaches the red portion of the ultra-violet spectrum. Furthermore, red is easily seen against a predominantly green background in many environments and probably serves as a flag for the foraging hummers. Since all hummers feed on nectar and on flowers with common characteristics, they tend to segregate themselves into differing habitats. This serves to minimize competition between the species.

The following is a list of flowering plants that will prove attractive for foraging North American species of hummingbirds.

Flowering plants native to the Sonoran Desert
Many of the following plants are available in better nurseries
(many non-native, nectar-producing flowering plants also attract hummingbirds)