In our desire to provide sources of nectar for insects, we often are tempted to plant exotic plants which can provide beautiful flowers for the garden and hopefully nourish some of our “flying flowers”, the wonderful butterflies. It is not always obvious how to balance native and exotic plants in the garden since certainly one would prefer to use native plants whenever possible. However natives may not always flourish in a given place, and they may not provide abundant flowers at all times of the year. Of course many of us inherited plants in our gardens when we purchased a house and find it difficult to remove flourishing but perhaps non-productive flowering exotics. One problem I face in our yard is that of plumbago, the shrub from S. Africa that is widely planted in Florida, Texas and California. It has pretty blue flowers, blooms profusely and is non-invasive. So is it a “good exotic” to have in the garden? The answer is NO ! But the reason may surprise you- not just because it is an exotic but because its the nectar in its flowers is not available to most insects in N. America. Look at the attached photo I took in our yard of a honeybee hopefully checking out the plumbago for a quick lunch- but to no avail. The problem is that the corolla tube, where the petals are fused into a long tubular structure holding nectar at the bottom, is very long relative to the length of the tongue or proboscis of the bee, or almost any other local insects. Thus they can look but not drink! So this flower is essentially useless as a provider of nectar for butterflies. In its native S. Africa it is known to attract butterflies and to act as a larval food plant. Some birds have figured out a solution to this problem by piercing the base of the flowers and “stealing” nectar.
Another common example of this problem with long corolla tubes is Ixora, the beautiful red tubular flower from India. Once you recognize this situation you can now examine your garden for unproductive flowers, at least from the perspective of hungry nectivores. This will require a fundamental change in your perspective about your garden- to carefully re-examine all of your plants on the basis of their usefulness to butterflies. So get out there and watch each of your flowers and see if the butterflies are actually able to feed from them.
Bill Dunson, Englewood, FL & Galax, VA