Jesse Durko calls his red pentas stock, "old-fashion'" red pentas, meaning the variety is an older type which has not been hybridized to the hilt. This pentas may not have as bold and dense flower head as newer varieties, but breeding flowers for those characteristics often veils or loses the intensity of the plant chemicals loved by butterflies and hummingbirds. With pentas it is pheromones. color, flower shape and nectar which those highly desirable hummingbirds and butterflies are after.
Biologically, one might also make a case that the more loose flower heads provide a more stable landing area for the butterfly, and a less confusing target for the hummers than a dense infloresecence forms.
At the end of the day, in the nursery, the old red pentas varieties do not disappoint when it comes to red color and attracting the desirable garden wildlife we want to see.
Sometimes people feel wary about red pentas, a misfortunate thing which happens to many a good plant because it has been used incorrectly and ends up an eyesore. Overcrowding is the nemesis of a red pentas bed. An overcrowded pentas bed will develop yellow leaves, bare spaces at the plant base, and the typical insects and pests of overcrowded plants.
This plant matures at 3' and should not be used where a dwarf height (18") is expected. Spacing in a row or bed should be on 3' centers.
Red pentas is an essential for butterflies and hummingbirds, but it is prudent to expect to replace it every two years or so. That is, it needs replacing after so many "cutting backs" when used in mass plantings rather than isolated clumps.
This planting shows pentas and salvia in a mixed planting which has naturalized on its own. Maintenance of this sort of planting is basically snip and clip the stray shoots. Naturalized gardens of varying leaf shapes will keep a filled in appearance because wherever there is new space available for light, a leaf will find it.
Red pentas is not a xeriscape plant and will develop black spots on the leaves if planted in poor drainage.
It will do well in the ground on water restrictions; if planted in nursery mix or composted soil it will look its best.
If you like container gardening, a single pentas grown out and lightly pinched to keep it bushy works well. Or, try a single pentas with ruellia and a shrimp plant for a charming mixed flower urn. When you are lounging on the patio with friends and that hummingbird comes right up to your flower urn for a sip, that's entertainment!