Mt. Cuba Center Research Report - Phlox for the Mid-Atlantic Region Mt. Cuba Center Phlox for the Mid-Atlantic Region - Page 17

SUN PHLOX Swallowtail Host Plants Eastern Tiger Swallowtail American hornbeam (Carpinus caroliniana) Ash (Fraxinus spp.) Birch (Betula spp.) Elm (Ulmus spp.) Hawthorn (Crataegus spp.) Maple (Acer spp.) Serviceberry (Amelanchier spp.) Sweet bay (Magnolia virginiana) Tulip tree (Liriodendron tulipifera) Black cherry (Prunus serotina) Willow (Salix spp.) Spicebush Swallowtail Eastern Tiger Swallowtail nectaring on Phlox paniculata 'Jeana' It’s relatively simple to determine which selections are most preferred by butterflies. However, it is much more difficult to determine why 'Jeana' is preferred to such a greater extent than other similarly healthy and floriferous cultivars. In fact, the incredibly small flower size of 'Jeana' might make you suspect it would be the least loved, since the flowers are so atypical for Phlox paniculata. A graduate student at the University of Delaware, Keith Nevison, attempted to answer this question by examining the nectar produced by 'Jeana' and several other cultivars. In theory, a greater quantity of nectar or a higher concentration of sugar would be a more desirable food source for butterflies, thus attracting more to the plant. After measuring these qualities, Nevison found no correlation between the increased visitation of 'Jeana' and its nectar volume or sugar content relative to other cultivars. Further sampling by Mt. Cuba Center intern, Caitlynd Krosch, supported Nevison’s assessment that these nectar characteristics are not good predictors of butterfly preference. Spicebush (Lindera benzoin) Common sassafras (Sassafras albidum) Sweet bay (Magnolia virginiana) Tulip tree (Liriodendron tulipifera) Host Plant Spotlight A fantastic small tree that can be added to almost any home landscape to support swallowtail butterflies is sweet bay (Magnolia virginiana). A mature tree grows approximately 20’ tall and bears large (2-3” wide), white flowers in summer. Although still unproven, the theory put forth by Nevison is that perhaps the smaller flower size, especially the narrowness and shallowness of the flower tube, is actually preferable because it allows butterflies to quickly access the nectar of many flowers without moving as frequently. Of course, supporting butterflies is not as simple as planting a garden full of Phlox paniculata 'Jeana'. While this cultivar is great at feeding adult butterflies, it is important to remember that all butterflies start out as caterpillars—many of which require specific host plants in order to become winged adults. Swallowtails were some of the most frequent visitors to our phlox trial and especially 'Jeana'. The caterpillar stage of this butterfly feeds on several species of native trees (see sidebar). It’s easy to support the entire lifecycle of this butterfly simply by including one of its host plants in your landscape. 17