Pentas are rising stars in more ways than one. Their name means “five” and their five-pointed blooms also explain their common moniker—"star cluster." “Egyptian” sometimes is added to that, as the plants originated in the hot, dry climates of Africa and the Middle East.
Therefore, though perennials in those parts and in USDA zones 10 through 12, they generally are grown as annuals. Where they are hardy, they can reach the 6-foot height of shrubs, but usually won’t surpass 1 to 3 feet elsewhere. Gardeners in zone 9 might be able to overwinter them in flowerbeds there too, as long as they are protected from frosts.
Pentas prefer what most blooming plants do: “moist, fertile, well-drained soil in full sun.” But they can star in partial shade also as long as their feet don’t get too wet. Since they are somewhat prone to root rot, well-drained ground is essential in their case. Because a few of my plants suffered from chlorosis one year, I suspect that soil should be mildly acidic as well.
As their species name lanceolata implies, pentas’ foliage is lance-shaped, while the flowers generally appear in shades of red, pink, purple, or white. There even is one variegated type, pictured above, appropriately named ‘Stars and Stripes.’ Although each five-pointed bloom is small—usually less than 1/2-inch across—those flowers band together to form "constellations" about 4 inches in diameter.
I call pentas rising stars because their popularity with butterflies and hummingbirds makes them a must-have these days. According to Tropical Flowering Plants, the blooms are loved by such flutter-bys as Schaus swallowtails, malachites, and zebra broadwings.
Because pentas plants take about three months to bloom from seed, you’ll need to start them early if you want them to perform all summer. I can tell from the date on their photo that the red and white ones pictured in the banner flowered for me in a pot in early November a couple years back. I’m guessing that they hadn’t bloomed yet when frost threatened, so I must have dug them up and placed them under grow lights until they did.
Although you can keep pentas indoors as houseplants over winter, they tend to sulk a bit there. So be careful not to overwater them, and avoid pruning them during that season. Once spring arrives and the plants begin to grow again, both those in pots and those in the ground should be cut back to keep them bushy.
When sowing pentas, you may want to purchase pelleted seeds, since they are easier to space. Press them into the surface of damp seed-starting mix without covering them and place their container under a grow light at warm temperatures. Under those conditions, the seedlings often pop up within 4 or 5 days.
Since our weather has become so soggy here, I’ll probably put my pentas in pots or grow-bags this year rather than in the ground. When watering the plants, you’ll want to avoid getting their leaves wet, as that foliage is somewhat susceptible to fungal infections. But, once you try pentas, you’ll thank your lucky stars that you did!
Photos: The banner image is my own. The 'Stars and Stripes' image is by ampy and the final photo by Todd_Boland, both from the Dave's Garden PlantFiles.