Geum spp.

Avens (Geum spp.) are certainly not counted among the most common perennials, despite having been cultivated in gardens for many years. Evocative of miniature roses, their brightly colored flowers bloom freely for many weeks in late spring and early summer. Avens are without doubt extroverted perennials—Graham Stuart Thomas fittingly proclaimed avens to be “one of the gayest of early summer plants.” And yet, avens have been uncommon in contemporary gardens until recently.

Avens in Great Britain far surpass what’s commercially available in the United States based on a review of the Royal Horticultural Society’s online plant finder (rhs.org.uk/plants/search-form) and the University of Minnesota Libraries’ Plant Information Online (plantinfo.umn.edu/). Developments in plant breeding and selection has drawn these lovely and tough perennials out of obscurity. Much of the enhancements to avens in the past few years can be attributed to Brent Horvath, plant breeder and owner of Intrinsic Perennial Gardens in Hebron, Ill. His Geum Cocktails series has re-imagined avens, offering gardeners a variety of flower colors ranging from soft pastels to fiery tones of red, orange, and yellow. As gardeners discover or rediscover avens, they will find that the offerings are greater than ever before.

It’s not surprising that the single to semidouble flowers resemble small roses, since Geum is in the rose family. Single flowers are saucer-shaped with five broad, showy petals and a central boss of stamens; whereas, semi-double flowers possess many more petals and fewer stamens. Red, orange, and yellow are the standard flower colors, but color intensity ranges from soft to deeply saturated, and may be blushed with other colors or bicolored, too. The flowers are held above the foliage on wiry stems and each blossom may be up-, out-, or down-facing depending on the species or cultivar. While the majority of avens show off their petals, the nodding flowers of water avens (G. rivale) and prairie smoke (G. triflorum), hide their understated corollas within cup-shaped coronal bracts. The feathery plumes of ripening fruit aid in seed dispersal but can also be exceptionally ornamental as in the case of the ethereal prairie smoke. Avens form rosettes of large hairy green leaves, which are comprised of a prominent terminal lobe above pinnately arranged pairs of smaller leaflets. The true leaf form and size is often masked since only the large terminal lobes show, while the small lateral leaflets are well hidden within the congested crowns and are often misshapen. Due to the hybrid nature of many cultivars, foliar shapes can be highly variable, thereby making taxonomic verification challenging. Leaves may be evergreen to semi-evergreen in mild winters.

There are about 50 species of Geum indigenous to cool regions in Europe, Asia, Africa, and the Americas, although only a handful of species are commonly cultivated. Many species, such as Chilean avens (G. chiloense) and scarlet avens (G. coccineum), grow naturally in moist, rich soils in meadows or woods; whereas prairie smoke (G. triflorum) is native to dry prairies and rocky places. Avens generally prefer moist, well-drained soils in full sun to light shade but do not like wet winter soils. They flourish in full sun gardens in cooler zones if ample water is provided but will appreciate afternoon shade in hot and humid climates. Avens are generally hardy in USDA Hardiness Zones 3-9.

The evaluation study

The Chicago Botanic Garden (USDA Hardiness Zone 5b, AHS Plant Heat-Zone 5) evaluated 49 Geum taxa between 2007 and 2015. Forty-six taxa completed at least two years in the trial, although the majority of the taxa were evaluated for four years. Three taxa were excluded from the final results because they were evaluated for one year only. The goal of the comparative trial was to identify outstanding avens for upper midwestern gardens. Five plants of each taxon were grown in side-by-side plots for easy comparison of ornamental traits and landscape performance. The evaluation garden was openly exposed to wind in all directions and received at least ten hours of full sun daily during the growing season, which averaged 181 days per year for the trial period. The clay-loam soil had a pH of 7.4 throughout the evaluation term. The site was normally well drained, but at times the soil retained moisture for short periods in summer and winter. G. canadense was planted in a partially shaded site that had a similar soil type and alkaline pH as the full-sun garden. Maintenance practices were kept to a minimum, thereby allowing the plants to thrive or fail under natural conditions. Trial beds were irrigated via overhead sprinklers as needed, mulched with composted leaves once each spring or summer, and regularly weeded. Moreover, plants were not deadheaded, fertilized, winter mulched, or chemically treated for insect or disease problems.

The performance report

In the spring of 2007, 26 taxa were planted in the full-sun trial garden; the remaining 23 taxa were added to the trial between 2008 and 2012 as new introductions became commercially available. All plants were evaluated for their cultural adaptability to the soil and environmental conditions of the test site; disease and pest problems; winter hardiness or survivability; and ornamental qualities associated with flowers, foliage, and plant habits. Final performance ratings are based on flower production, foliage and habit quality, plant health and cultural adaptability, and winter hardiness during the trial period.

Sixty percent of the taxa received five-star excellent or four-star good ratings for their overall performance in the trial. Top-rated plants displayed superior flower production, attractive foliage, robust habits, adaptability to the growing conditions of the site, and winter hardiness.

The outstanding five-star rated avens included Geum ‘Mai Tai’, ‘Sangria’, ‘Totally Tangerine’ and G. triflorum. ‘Mai Tai’ is one of the new avens with Midwestern roots—bred by Brent Horvath in Hebron, Ill. Apricot-flowered ‘Mai Tai’ is a delightful departure from the hot-color palette so typical of the group. Flowers open a muted red, fading to apricot with striking burgundy sepals and flower stems. The outward-facing, semi-double flowers bloomed generously from late April to early June and then again sporadically later in the summer. ‘Mai Tai’ averaged 24 inches tall and wide with flowers; without flowers the rounded foliar mound was 10 inches tall.

Like ‘Mai Tai’, ‘Sangria’ is also part of the Geum Cocktail series and was one of the last avens to begin blooming, typically in early to mid-June. Its dazzling scarlet flowers—semi-double and upwardfacing—were borne profusely for more than a month and then rebloomed in August. The robust mounds topped out at 16 inches tall and 30 inches wide but the flower stems extended the height to 30 inches.

‘Totally Tangerine’ (synonym ‘Tim’s Tangerine’) shared an exuberance of bloom and plant size with ‘Sangria’. The branched floral stems, to 29 inches tall, were crowded with upward- and outward-facing tangerine-orange blossoms from late May to mid-July, and sometimes a bit longer due to the sterile nature of the flowers. We described the floral form as semi-double because each blossom had a few more petals than a typical single flower but far fewer than other semi-double cultivars. A robust mounded habit and an exceptionally floriferous nature set ‘Totally Tangerine’ apart from most other avens. G. triflorum, prairie smoke, is often characterized as a native plant, but its superior ornamental traits and cultural adaptability make it a great garden perennial. Its curious flowers—in groups of three—nod like a shepherd’s crook with the creamy white petals hidden beneath rosy pink spurred caps. The distinctive fruits developed while flowers were still blooming strongly; long feathery tails on maturing seeds turned silvery and pink, looking like puffs of smoke above the plants. The ferny foliage, strongly dissected into many leaflets, stayed attractive as long as the plants were kept moist. Prairie smoke is known to go dormant in severe drought conditions.

Ornamentally, avens offer an array of flower colors and forms, generally prodigious flower production, attractive albeit somewhat coarse foliage, and variably mounded habits. Floral forms ranged from single to semi-double, and nodding to upward- and/or outward-facing; flower size ranged between 1-2 inches wide. Among the taxa exhibiting colorful calyces and stems were ‘Alabama Slammer’, ‘Cherry Cordial’, ‘Cosmopolitan’, ‘Mai Tai’, ‘Spanish Fly’, ‘Tequila Sunrise’, ‘Wet Kiss’, G. rivale, and G. rivale ‘Leonard’s Variety’. The plumose fruits of G. triflorum and G. montanum were the most ornamental among the avens; whereas, the fruits of G. coccineum, G. rivale, and G. urbanum were not as strongly feathered nor as colorful. Although seedlings were infrequently observed in the trial, G. urbanum was a consistently vigorous reseeder.

The majority of taxa were determined to be winter hardy with some exceptions noted. ‘Banana Daiquiri’, ‘Coppertone’, and G. montanum were winter-killed after growing successfully for two years. Plants of ‘Mrs. Bradshaw’ lived for three years before dying in the winter of 2011-2012. All plants of G. urbanum died during two consecutive winters (2008-2009 and 2009-2010) but vigorous seedlings replaced the plants in each of the following springs. Only in the winter of 2010-2011 did all plants of G. urbanum make it through winter without injury—seedlings were also present in spring 2011. Geum ‘Blazing Sunset’ was never successfully overwintered despite being replanted in 2008, 2009, and 2010. Geum ‘Feuerball’, ‘Lady Stratheden’ and G. quellyon ‘Double Bloody Mary’ died the first winter (2007-2008) but were not retested. Incidentally, ‘Lady Stratheden’ is also known as ‘Gold Ball’, but plants sold under that name were not included in the trial. The greatest plant losses and crown injury were observed during the winters of 2007- 2008 and 2013-2014, although winter injury was noted in every year of the trial between 2007 and 2015. In addition to the losses noted above, the highest attrition or crown damage was incurred by ‘Cherry Cordial’ (first attempt failed, second attempt succeeded), ‘Pumpkin’ (first attempt failed, second attempt died in third winter), ‘Sunrise’ (severe crown injury in first winter, complete plant loss the second winter), and G. coccineum (severe crown loss in multiple winters). Avens with no winter losses or crown injury observed during the trial period included ‘Beech House Apricot’, ‘Borisii’, ‘Citronge’, ‘Cosmopolitan’, ‘Fire Lake’, ‘Fire Storm’, ‘Flames of Passion’, ‘Georgenburg’, ‘Gimlet’, ‘Limoncello’, ‘Lisanne’, ‘Mai Tai’, ‘Rijnstroom’, ‘Spanish Fly’, ‘Summer Hummer’, ‘Totally Tangerine’, G. canadense, G. coccineum ‘Eos’, G. coccineum ‘Werner Arends’, G. × intermedium ‘Diane’, G. rivale, G. rivale ‘Album’, G. rivale ‘Leonard’s Variety’ and G. triflorum.

A strong case for avens

Avens are not common garden plants but their performance in the trial demonstrated that they should be grown more widely. The avens of old are being supplanted by a new crop of contemporary hybrids with a wider range of flower colors. Just over 60 percent of taxa in the trial received good or excellent ratings—‘Mai Tai’, ‘Sangria’, ‘Totally Tangerine’, and G. triflorum were the highest rated plants. In the end, there was a good mix of old and new varieties among the top performers. Avens are notably ornamental, exhibiting a range of flower colors and forms, bountiful floral displays, bold-textured foliage, and robust habits.

The introduction of so many new and unique avens in recent years is exciting for gardeners. Avens are proven to be tough plants that require minimal maintenance and offer a variety of flower forms and colors. Gardeners looking for something different need look no further than vibrant spring-blooming avens. For the entire trial report, visit www.chicagobotanic.org/research/ornamental_plant_research/plant_ evaluation.

Richard G. Hawke is the plant evaluation manager at the Chicago Botanic Garden. Hawke and his team evaluate herbaceous and woody plants in comparative trials.