The chokeberries (Aronia spp.) are a group of underused shrubs that have many possibilities for landscape use. These shrubby members of the Rose family (Rosaceae) are multistemmed; deciduous; and are cultivated for their flowers, foliage, and fruits. Several taxonomic and genetic studies on species relations within the genus have been published but in short, there are four recognized species, three native to North America—Aronia arbutifolia (L.) (red chokeberry), Aronia melanocarpa (Michx.) Ell. (black chokeberry), and Aronia prunifolia (Marsh.) (purple chokeberry)—and a fourth cultivated taxon, Aronia mitschurinii, that is an intergeneric hybrid with Sorbus aucuparia. The latter shrub has large pomes used for fruit production in eastern Europe, Russia, and the United States (Brand 2010; Hardin 1973; Leonard et al. 2013). Recently the genus has been cultivated in Korea for the antioxidant properties of the fruits (Hwang and Thi 2016; Kim et al. 2021). Chokeberries in the wild grow in a variety of conditions from dry sandy and rocky soils to bog and swamps; under cultivated conditions, they are appreciated for their tolerance and adaptability to unfavorable growing conditions. Black chokeberry has highly attractive, shiny, deep-green main season foliage that transitions to a pleasant combination of burgundy, copper, and gold in autumn, with some recent introductions turning bright red in the fall. The species blooms in May producing rounded inflorescences that last for a week to week and a half. Aronia melanocarpa generally produces black fruit, but ‘UCONNAM166’ is triploid and produces few to no berries. The new cultivar UCONNAM166 has the desirable ornamental traits of the species in general, and it also has the additional positive attributes beyond that of typical black chokeberries, including that it is non-rhizomatous; has upright vigorous growth, narrow compact form, and robust large, shiny leaves; and does not produce fruit.
‘UCONNAM166’ is a release of the University of Connecticut Aronia breeding program that was started in the early 2000s with the goals of developing unique and improved ornamental cultivars for landscape use. Additional releases from the UCONN program include the low growing cultivars ‘UCONNAM165’ and ‘UCONNAM012’ (Brand 2024).
Origin
‘UCONNAM166’ is a hybrid of ‘UCONNAM012’ as the maternal parent and Aronia mitschurinii ‘Viking’ as the pollen parent. ‘UCONNAM012’ is an open-pollinated seedling that originated from diploid A. melancarpa seed collected near South Thomaston, ME, USA, that was subsequently grown and selected in a research nursery in Mansfield, CT, USA. ‘UCONNAM012’ has been patented and licensed and is now being sold under the trade name Ground Hug® (Brand 2024). ‘Viking’ is a cultivar of Aronia mitschurinii, which is an intergeneric hybrid tetraploid species that is 25% Sorbus aucuparia and 75% A. melanocarpa (Leonard et al. 2013). ‘Viking’ has large fruits and is used as a berry crop in eastern Europe, Russia, and the United States. Tetraploids are generally apogamous and less likely to set true sexual seed (Brand et al. 2022). Therefore, the diploid ‘UCONNAM012’ was used as the seed parent. Aronia is protogynous with the stigmas maturing before the anthers making effective emasculation possible. In 2010 in a pollinator-free greenhouse, 75 ‘UCONNAM012’ flowers were emasculated and pollen of ‘Viking’ applied. The pollinations resulted in 27 fruits containing 86 seeds. All seeds were stratified and planted in 2011, but only two germinated. One seedling did not survive, but the remaining seedling was noted to be vigorous and non-rhizomatous, with glossy, attractive foliage and a clean upright compact form. This seedling was named ‘UCONNAM166’ (Connolly 2014).
Description
‘UCONNAM166’ has a distinctly upright plant form and is non-rhizomatous unlike many other cultivars, including ‘UCONNAM012’, ‘UCONNAM165’, Autumn Magic, Hugin, and Morton Iroquois Beauty™. The growth form of the new cultivar is more controlled and compact compared with ‘Viking’, its paternal parent (Fig. 1). ‘UCONNAM166’ reaches a mature height between 1 and 1.5 m and a width of ≈1 m. The leaves of ‘UCONNAM166’ are alternate, elliptical to obovate, and ≈10 cm long by 6 cm wide, with cuneate to obtuse bases and with acute to cuspidate leaf apices (Fig. 2). The leaf margins are evenly crenate. The adaxial (upper) leaf surface is smooth and very shiny, whereas the abaxial (lower) surface is slightly rough, waxy, and very slightly pubescent. Young leaves on the upper surface are close to Royal Horticultural Society (RHS) yellow-green (144A). Lower surface colors for young leaves are close to RHS yellow-green (146D). All colors in the descriptions for ‘UCONNAM166’ were designated using the RHS color charts (Royal Horticultural Society 2007). The upper surface of mature foliage is green (RHS 137A), whereas the lower surface is near yellow-green (RHS 146C).
(Left) ‘Viking’ compared with (right) ‘UCONNAM166’. ‘UCONNAM166’ has a densely branched, controlled and upright habit. (Photo: Mark Brand)
Citation: HortScience 59, 7; 10.21273/HORTSCI17858-24
(Top) Leaves of maternal parent ‘UCONNAM012’, (middle) the new cultivar ‘UCONNAM166’, and (bottom) paternal parent ‘Viking’. (Photo: Mark Brand)
Citation: HortScience 59, 7; 10.21273/HORTSCI17858-24
‘UCONNAM166’ flowers in early May (Connecticut, USA), with the blooming period lasting between 1 and 2 weeks (Fig. 3). There are typically 30 to 40 flowers per lateral stem. Flowers are produced in corymbs composed of outward-facing flowers. Corymbs are 2 to 3 cm in height and width, and mostly contain between 5 and 10 flowers. Individual flowers are symmetric and rotate, with five petals and a diameter of 12 to 14 mm. Flower color is white (RHS 155B) and may display a blush of red-purple (RHS 62C) at first opening. ‘UCONNAM166’ is triploid and generally sterile; rarely, it sets a small pome fruit ≈8 mm in diameter in late summer. Fall leaf color for ‘UCONNAM166’ in full sun exposure is a mix of red and yellow displaying RHS 43B blotched with RHS 13B on the upper surface, with the lower surfaces turning red RHS 43D flushed with orange 25C and yellow RHS 13B blotches (Fig. 4).
‘UCONNAM166’. (Left) View of full shrub in flower. (Right) Close-up of inflorescences. (Photo: Spring Meadow Nursery)
Citation: HortScience 59, 7; 10.21273/HORTSCI17858-24
Brightly colored fall foliage of ‘UCONNAM166’. (Photo: Mark Brand)
Citation: HortScience 59, 7; 10.21273/HORTSCI17858-24
Landscape Use and Culture
Plant performance statements and recommendations are based on information provided by the collaborators of Spring Meadow Nursery (Grand Haven, MI, USA) and the Proven Winners Program, as well as performance in landscape installations at the University of Connecticut campus in Storrs, CT, USA. ‘UCONNAM166’ has performed well in regions as cold as USDA hardiness zone 3 and as warm as zone 8 (US Department of Agriculture, Agricultural Research Service 2023). This cultivar is adapted to full sun or partial shade conditions and is tolerant of challenging landscape situations, including dry soils, once established. The upright non-rhizomatous form of ‘UCONNAM166’ is useful in smaller landscapes and where large shrubs are unwanted. This cultivar is an excellent choice for durable mass plantings or low- to medium-sized hedges. This small-medium shrub stature allows ‘UCONNAM166’ to be useful as a substitute for other low-medium growing deciduous shrubs, such as certain species of Berberis, Ligustrum, or Euonymus. Like the invasives, this cultivar can be trained into hedges and has colorful fall foliage, although ‘UCONNAM166’ is mostly sterile and is unlikely to establish in native habitats.
‘UCONNAM166’ is ornamental throughout the year, with white May flowers; shiny, deep-green summer leaves; and a burgundy-copper to gold fall display. ‘UCONNAM166’ is triploid and produces few if any fruits, making this cultivar more suitable than other Aronia cultivars to be planted along walkways or other hardscape elements that would otherwise be stained by falling black chokeberries in late summer and fall.
Clonal Propagation
‘UCONNAM166’ propagation is the same as for ‘UCONNAM012’ and ‘UCONNAM165’ (Brand 2024). This cultivar is propagated easily by softwood cuttings collected from mid-June to mid-July. Rooting percentages of >90% and profuse root systems can be expected. Peatmoss:perlite (50:50, vol:vol) or similar propagation media and intermittent mist work well to root cuttings. Cuttings can be double-wounded and treated with 3000 ppm indole-3-butyric acid. Rooted cuttings can be potted and fertilized to produce new growth, and they overwinter well without losses.
Micropropagation can also be used to propagate ‘UCONNAM166’ clonally. Shoot multiplication in vitro can be achieved using Murashige and Skoog medium and vitamins (Murashige and Skoog 1962), 0.5 mg⋅L–1 benzyladenine, 3% sucrose, and 0.8% agar with a pH of 5.7 (Brand and Cullina 1992). Cultures should be maintained at ≈25 °C, with a 16-h photoperiod of 40 μmol⋅m–2⋅s–1 provided by cool-white fluorescent lights or appropriate light-emitting diode (LED) lighting, with a subculture cycle of between 28 and 35 d. At least an 8× shoot multiplication rate can be expected. Microshoots are rooted easily (near 100%) under nonsterile conditions in clear, plastic salad trays containing a 1:1 (vol:vol) peatmoss:vermiculite mix under fluorescent or LED lighting. Microcuttings root in 3 weeks and can then be acclimated to drier air over a period of 10 to 14 d before being moved to a greenhouse. Greenhouse acclimation is aided using clear, plastic, humidity dome covers and 50% shadecloth.
Availability
‘UCONNAM166’ has been patented by the University of Connecticut (Brand and Connolly 2018). This cultivar has been licensed exclusively to Spring Meadow Nursery, Grand Haven, MI, USA, and is part of the Proven Winners® product line of flowering shrubs. ‘UCONNAM166’ has been assigned the trade name Low Scape Hedger®.
References Cited
Brand MH. 2010. Aronia: Native shrubs with untapped potential. Arnoldia. 67:14–25.
Brand MH. 2024. ‘UCONNAM012’ (Ground Hug®) and ‘UCONNAM165’ (Low Scape Mound®): Two low-growing cultivars of black chokeberry (Aronia melanocarpa). HortScience. 59:462–464. https://doi.org/10.21273/HORTSCI17663-23.
Brand MH, Connolly BA, 2018. Aronia plant named ‘UCONNAM166’. University of Connecticut Technology Commercialization Services (assignee). US Plant Patent 28,83. (Filed 10 Feb 2016, granted 2 Jan 2018).
Brand MH, Cullina WG. 1992. Micropropagation of red and black chokeberry (Aronia spp.). HortScience. 27:81. https://doi.org/10.21273/HORTSCI.27.1.81.
Brand MH, Obae SG, Mahoney JD, Connolly BA. 2022. Ploidy, genetic diversity and speciation of the genus Aronia. Scientia Hortic. 291:110604. https://doi.org/10.1016/j.scienta.2021.110604.
Connolly BA. 2014. Collection, description, taxonomic relationships, fruit biochemistry, and utilization of Aronia melanocarpa, A. arbutifolia, A. prunifolia, and A. mitschurinii (PhD Diss). University of Connecticut, Storrs, CT, USA. https://digitalcommons.lib.uconn.edu/dissertations/342/.
Hardin JW. 1973. The enigmatic chokeberries (Aronia, Rosaceae). Bull Torrey Bot Club. 100:178–184.https://doi.org/10.2307/2484630.
Hwang ES, Thi ND. 2016. Effects of different growing regions on quality characteristics, bioactive compound contents, and antioxidant activity of aronia (Aronia melanocarpa) in Korea. Prev Nutr Food Sci. 21:255–262.
Kim DW, Han HA, Kim JK, Kim DH, Kim MK. 2021. Comparison of phytochemicals and antioxidant activities of berries cultivated in Korea: Identification of phenolic compounds in aronia by HPLC/Q-TOF MS. Prev Nutr Food Sci. 26:459–468.
Leonard PJ, Brand MH, Connolly BA, Obae SG. 2013. Investigation of the origin of Aronia mitschurinii using amplified fragment length polymorphism analysis. HortScience. 48:520–524. https://doi.org/10.21273/HORTSCI.48.5.520.
Murashige T, Skoog F. 1962. A revised medium for rapid growth and bioassays with tobacco tissue culture. Physiol Plant. 15:473–497. https://doi.org/10.1111/j.1399-3054.1962.tb08052.x.
Royal Horticultural Society. 2007. Royal Horticultural Society Colour Chart (5th ed). RHS Media, Royal Horticultural Society, London, UK.
US Department of Agriculture, Agricultural Research Service. 2023. Plant hardiness zone map. https://planthardiness.ars.usda.gov/. [accessed 1 Dec 2023].