Botanical name: Pentas lanceolata
Family: Rubiaceae (Madder)
Origin: Eastern tropical Africa to Saudi Arabia
Display period: All summer
Height: 1 to 4 feet
Pentas is one of those plants that might be said to fall between the cracks. You won't find it mentioned in many books or widely offered in stores, and yet for non-stop summer bloom on my terrace and no more care than watering, this little-known, showy flower was unsurpassed.
The plant is usually classed as a subshrub, although the terms herb and tender perennial are also used to describe it. The designation subshrub is based on the plant's hardiness in the South, where it also receives the hot, dry conditions that are so to its liking, and where it's most widely found. But let the thermometer inch toward freezing and pentas will vanish as completely as if it were an annual.
Pentas develops woody stems as it matures, in some cultivars reaching a height of 3 feet. These traits also contribute to its ranking as a subshrub.
I discovered pentas on a visit to Clifford Egerton Greenhouses, a wholesale grower in Baltimore, when it was shown to me as a new offering. The variety was a dwarf type that's suited to hanging basket display and edging a bed.
Jim Nau, trials manager at Ball Seed Co. in West Chicago, Ill., and a major supplier of pentas to the trade, calls pentas a specialty item. For plants to endure heat and drought, he says, they must first become established in the ground while it is still cool and temperatures remain in the '60s. Pentas may also be grown in a sunny window as a house plant. Propagation is done by seeds or cuttings.
Mr. Nau's favorites are the taller types, especially Ruby Glow, which he likes to see featured in a mass on a mound at the center rear of a border and ringed with blue Victoria salvia. Pentas also comes in white, lavender and pink. In Ball's flower trials, Mr. Nau notes, pentas blooms without letup and except for watering, never needs any other help. Pentas, by the way, was first listed in a nursery catalog in 1900.