A tantalizing trio

I’ve grown, observed and photographed many seasonal plants over the last 25 years. I’m always excited to incorporate colorful annuals into beds, borders and containers. During my 21 years at Rotary Botanical Gardens in Janesville, Wisconsin, we would plant roughly 150,000 annuals every year representing over 900 varieties. It was interesting to see what thrived (or didn’t), popped, intrigued and otherwise engaged our visitors.

A few of my favorite, indispensable seasonal plants are included in this tribute to a tantalizing trio; Acalypha spp., Ageratum spp. and Pentas spp. Every year, I continue to grow many varieties of each of these amazing seasonals that have proven ornamental value, presence in the landscape and when given a little TLC, will thrive.

Acalypha

Technically an evergreen shrub native to Fiji and neighboring South Pacific islands, what is commonly called copperleaf or Jacob’s coat (Acalypha wilkesiana) is a seasonal plant (Euphorbiaceae family) for most of us unless you are in southern Florida (hardy in Zones 10-11). My experience in the Midwest has been exciting as there are so many excellent selections of copperleaf available that warrant use in bedding schemes and containers. Light, well-drained, fertile soil is ideal along with a protected location that receives ample sunlight to bring out the best foliage coloration. Full or part sun settings are acceptable. Soils should be consistently moist to retain foliage with any significant dry periods leading to leaf drop.

Make no mistake that we’re growing this species for amazing foliage with a range of colors and leaf textures. Prized for these brilliant colors and leaf patterns, the shiny, coarsely toothed leaves (usually 4-8 inches in length) have instant impact and these plants grow to about 24-30 inches for me in Wisconsin. I imagine they will get taller in warmer climates, but stems can be pinched back to manage size and shape while also increasing bushiness. The insignificant male and female flowers are on the same plant, but their ornamental appeal is limited and obscured by the fantastic foliage display. Plants are commonly propagated by leaf and stem cuttings with bottom heat. Although generally disease free, do watch out for occasional mealybugs, whitefly, scale and spider mites. Copperleaf can be a nice houseplant as well but needs warm, humid and bright conditions.

My favorite copperleafs for foliage patterns include two in the Tiki Series; ‘Jungle Cloak’ and ‘Peach Whirl’. Every leaf is a piece of art. ‘Copperhead’ features an amazing maroon and red combination and ‘Kona Gold’ offers a bright splash of yellow in the landscape. For a finer texture with narrow foliage, check out ‘Sizzle Scissors’ and two more Tiki selections; ‘Firestorm’ and ‘Tahitian Halo’. For maximum ornamental appeal in the space they grow and occupy, you can’t do much better than Acalypha wilkesiana selections.

Ageratum

There is a reason why Ageratum houstonianum and cultivars continue to be so popular. Commonly known as flossflower, this native of Mexico, Guatemala and Belize has a long track record as a frost-tender, seasonal bedding plant (Asteraceae family). While the most seen varieties feature blue-toned flowers, there are also white and pink selections. Do note that in warmer climates, this plant has become a major weed, so caution is warranted. I’ve used many of the blue varieties as a “cooling color” with most selections under 15 inches in height. The shorter forms are excellent “edgers”, bedding components and container plants. Taller selections in the 24-30 inches range exist for both display and cutting purposes. Don’t confuse this plant with the “hardy ageratum” or “mistflower” (Conoclinium coelestinum) which has similar flowers but is hardy to Zone 5 and can be quite rambunctious.

Full sun locations are ideal although part sun is acceptable. Light afternoon shade is recommended in hot summer climates. Average, moist but well drained soils are preferred. Ageratum does have both heat and drought tolerance although available moisture needs to be part of the equation for extended success. I’ve rarely seen any issues with flossflower in the landscape and while there are few insect or disease problems, do be wary of possible aphids and whiteflies. Powdery mildew might appear in cool, damp summers or in situations with limited air circulation. This plant is toxic to grazing animals.

The newest flower clusters, borne in dense corymbs with thread-like ray flowers, emerge above the earlier, fading flowers so you’re always assured of some color contribution. Bees and butterflies will be equally delighted with the flowers! Deadheading of spent blooms isn’t essential but does keep the plant tidy and promotes continued bloom. I typically apply a low-strength fertilizer every three weeks over the growing season for flossflowers to look excellent all season long.

Dozens of excellent varieties of flossflower exist from seed and vegetative sources. You can find any shade of blue from purple to true blue and sky blue. Various pink tones are available as are many excellent, pure white options. Research mature height in advance. I’m a huge fan of the Aguilera Series, particularly ‘Dark Pink’ and ‘Purple’. Do check out the Patina, Artist, Bumble and Cloud Nine series as well. My favorite white variety is ‘Aloha White’ and my “go to” for a consistent blue is ‘High Tide Blue’. For an interesting shade of blue, explore ‘Patina Delft’ and ‘Bumble Silver’. The best cutting flossflowers in my opinion include ‘Everest Blue’ and ‘Timeless Rose’.

Pentas

Every winter I resolve to use more Pentas lanceolata in the garden. The flower power of this plant is extraordinary as is the additional benefit of attracting hummingbirds and butterflies to the garden. Referred to most commonly as Egyptian starcluster or Egyptian starflower, this member of the Rubiacea (madder) family is native to much of Africa as a woody-based perennial or subshrub. Domestically, it is a seasonal plant for most applications (Zone 10-11 hardy). These plants will reach 12-18 inches for me over a hot summer in Wisconsin. Full sun is preferred although the very lightest of shade can be tolerated. Rich, fertile, slightly acidic, well-drained soils are ideal although Pentas will thrive in average soils as well. A controlled release fertilizer or periodic fertilizer applications once per month will help with vigor and flowering. Deadheading spent blooms and pinching the plant back will result in subsequent flushes of new flower clusters. I time my fertilizer applications right after deadheading duties.

The 4-inch wide flower clusters feature many long-tubed, star-shaped, five-petaled flowers in shades of red, white, pink, magenta, lilac and white. Recent introductions have been bred to have larger flowers, a longer bloom period and some other novel improvements. The nectar-rich flowers are a magnet for butterflies and hummingbirds and are also a long-lasting cut flower. I use many of these heat-tolerant Egyptian starflower varieties in raised beds, planters and in bedding compositions that focus on pollinators. The dark green, lance shaped leaves have deep veins and some pubescence. The variety ‘Stars and Stripes’ displays a mottled variegation on the foliage and displays bright red flowers.

I’ve never met a Pentas that I didn’t like. There are myriad selections out there, all with their own merit and colorful nuances. Explore the BeeBright, Butterfly, Graffiti, HoneyCluster, StarCluster and Lucky Star series for a wide range of amazing color options. The Glitterati series features a white star pattern in the middle of every flower and comes in two selections: ‘Purple Star’ and ‘Red Star’. These are noticeably very cool. I’m also admittedly smitten with the Falling Star series which features three colors of trailing plants that are perfect for the basket, wall edge or container. The variety ‘Pink Bicolor’ is my favorite in this series and I use it often in sunny window boxes.

Pentas are generally disease-free although do scout for spider mites and aphids. This plant is also deer and rabbit resistant. I have grown Pentas from seed but find that in my shorter, Midwest growing season, purchasing established plants in spring is the way to go. Propagation is also accomplished by softwood cuttings. I’m surprised I don’t see more Pentas being sold, purchased and grown as this plant has a huge return on investment with lengthy color and the high probability of hummingbird sightings.

Mark Dwyer is currently the garden manager for the Edgerton (WI) Hospital Healing Garden after 21 years as director of horticulture at Rotary Botanical Gardens (Janesville, Wisconsin). He also operates Landscape Prescriptions by MD, a landscape design and consultation business. mcdwyer@zoho.com