Early-flowering Chrysanthemum ‘Clara Curtis’ in mum trial

Chrysanthemum ‘Country Girl’

Mixed seedlings in mum trial bed

The mums in the trial were informally categorized into three groups for comparative purposes: 1) garden mums, 2) landscape mums, and 3) cutflower or florist mums. The garden mums included ‘Autumn Bronze’. ‘Brandywine Sunset’, ‘Cambodian Queen’, ‘Campfire Glow’, ‘Clara Curtis’, ‘Country Girl’, ‘Emperor of China’, ‘Hillside Sheffield Pink’, ‘Mary Stoker’, ‘Peaches and Cream’, ‘Penelope Pease’, and ‘Sheffield Pink’. The landscape mums were ‘Autumn Spice Igloo’, ‘Firedance Igloo’, and ‘Harvest Igloo’, while ‘First Lady’, ‘Fine Feathers’, ‘Fred Stone’, ‘Happy Face’, ‘Ivory Pinwheel’, and ‘Yellow Starlet’ represented florist mums. 

Flower colors ranged from soft pastels such as the apricot-yellow of ‘Mary Stoker’ and the creamy yellow of ‘Ivory Pinwheel’ to the smoldering autumnal tones of ‘Campfire Glow’ and ‘Harvest Igloo’. Flower morphology included single, semidouble, and fully double forms, and flowers ranged in size from 1 to 3 inches wide. The earliest flowering cultivars opened between mid-July and early September, while later ones opened between late September and mid-October. See Table 1 for observed bloom times. There was a correlation between early bloom periods and lower overall ratings related to health and vigor; however, it was not absolute—the earlier flowering cultivar ‘Firedance Igloo’ had a high rating, while several poor performers were autumn-bloomers. Furthermore, semidouble- and double-flowered cultivars were generally weaker than single-flowered varieties regardless of their bloom times, except for ‘Autumn Spice Igloo’ and ‘Firedance Igloo’. 

Flower production and floral quality throughout the protracted bloom cycles factored into final ratings, but the truncated bloom periods specific to later-flowering cultivars did not unduly affect ratings. Unfortunately, early types such as ‘Clara Curtis’, ‘First Lady’, ‘Happy Face’, and ‘Yellow Starlet’ held onto brown deadheads throughout the long bloom periods and received lower final ratings in part for how the spent blooms detracted from their floral quality and diminished the overall display. Heavy flower production was observed on most taxa regardless of plant size; however, lower flower production was noted in several instances where plant vigor was weak in one or more years. Reduced efflorescence or flower production related to vigor was observed on ‘Clara Curtis’ in 2023 and 2024, ‘Fred Stone’ in 2023, and ‘Ivory Pinwheel’ in 2023. The mums were beneficial for late-season pollinators, especially flies and bees, which were common and frequent visitors up to hard frost. Additionally, moths and butterflies were common pollinators earlier in the season. 

The bloom cycle typically ended with a hard frost in early November each year; once again, the first frost date in the Chicago area occurs between October 11 and October 31, with October 15 commonly cited as the average date. Occasionally, light frost caused minor damage to flower quality prior to killing frosts, which were recorded between November 6 and November 9 in 2021 – 2025. No hard frosts were observed in October, which benefited mid-October bloomers such as ‘Brandywine Sunset’, ‘Cambodian Queen’, ‘Campfire Glow’, ‘Country Girl’, ‘Emperor of China’, ‘Hillside Sheffield Pink’, ‘Penelope Pease’, and ‘Sheffield Pink’. Considering the recorded frost dates observed during the trial, we cannot judge how long flowering would naturally occur with a later frost. However, for taxa that began flowering in early to mid-October, 80 to 100 percent of flowers were still open and ornamental at hard frost, so the bloom period might be expected to continue for several weeks longer if no killing frost occurred. Mums that began flowering in August or September typically had a small percentage of flowers still open in early November.

While accepting the synonymousness of ‘Hillside Sheffield Pink’ and ‘Sheffield Pink’ given their close resemblance, we observed that ‘Sheffield Pink’ was not as strong a plant by comparison. The differences in their phenotypic traits were subtle, yet enough that both are cited in Table 1. For example, the rays of ‘Hillside Sheffield Pink’ were flat, while ‘Sheffield Pink’ had involute or boat-shaped rays that made the flowers more pointed. The genetic makeup of plants sold as ‘Hillside Sheffield Pink’ and ‘Sheffield Pink’ is unknown, so although the names are deemed synonymous, the plants offered under these respective names are unlikely to be clonal duplicates. 

Habit quality after removal of seedlings

Pollinator on Chrysanthemum ‘Ivory Pinwheel’ [November 3, 2022]

Burgundy leaves of Chrysanthemum ‘Emperor of China’

Plant habits were generally mounded, with sizes ranging from 11 to 42 inches tall and 21 to 84 inches wide; ‘Harvest Igloo’ was the smallest and ‘Hillside Sheffield Pink’ was the largest in the respective ranges. All plants were floriferous and vigorous for the first two years in the garden, but the habit quality of some mums declined in subsequent years. Relaxed to floppy stems, gaps in the plant canopy, and/or uneven stem heights contributed to lower habit quality ratings. By the third year of the trial, plant crowns were patchier in spring, which sometimes corresponded to less uniformity in stem height later in the season. Loose crowns were primarily related to the rhizomatous growth habit, with shoots emerging each successive spring at the perimeter of bare centers. Even with loose crowns in spring, most plants bulked up in summer. The spacing of plants in the trial influenced plant habits in two ways. First, tall-stemmed plants were held upright by similarly sized neighboring plants, maximizing the floral display.

Plants were often constrained by adjacent plants, so widths may not be absolute. And second, taller plants outgrew and flopped onto shorter mums where planted side-by-side. Rain and overhead irrigation exacerbated floppiness, pulling down stems heavy with flowers, which was especially problematic for semidouble- and double-flowered cultivars. 

Reseeding can be viewed as a floral issue—spoiling the flower display with other colors—but seedlings were deemed more harmful to habit quality. As the mums aged, the open crowns provided space for vigorous seedlings to grow within the original plant; seedlings also sprouted on the perimeter and interspaces within the trial plot. Multiple cultivars in proximity likely amplified the creation of new flower colors. Distinguishing between original stems and seedlings was often difficult until flower buds formed late in the season. Occasionally, marked differences in stem height and foliage helped with identifying seedlings earlier. While the mix of flower colors created through natural hybridization was ornamental, seedlings—sometimes excessive—crowded and shaded out the original plant(s), resulting in uneven to open habits when the seedlings were removed. Mums such as ‘Brandywine Sunset’, ‘Cambodian Queen’, ‘Country Girl’, ‘Fred Stone’, ‘Ivory Pinwheel’, and ‘Peaches and Cream’ typically had the thinnest crowns in spring, so more seedlings were observed in their plots.

The lobed to dissected medium-green leaves provided texture and were generally healthy before flowers formed. Due to low light, the lowest and/ or interior leaves were often blackened when flowering began but were unseen unless stems splayed open. The leaves of ‘Emperor of China’ turned partially burgundy when blooming, which we initially took for a cultural issue but learned it is a predictable trait of the cultivar. Foliar diseases were uncommon and infrequent overall. Leaf spotting was noted on ‘First Lady’ in 2024 and ‘Clara Curtis’ in 2022 – 2024 and aster yellows was found on one plant of ‘Fred Stone’ in 2022. The infected plant was immediately removed.

More than half of the taxa survived four winters without any plant losses or crown injury observed. Crown injury in one year only was noted on ‘Autumn Bronze’, ‘Cambodian Queen’, ‘Happy Face’, and ‘Yellow Starlet’; ‘Brandywine Sunset’, ‘Emperor of China’, ‘Fred Stone’, and ‘Ivory Pinwheel’ were the taxa that suffered crown injury in consecutive winters. Ten of the 105 individual plants in the trial died in winter; ‘Fine Feathers’ was the only mum with all plants killed over successive years prior to the end of the trial.

Chrysanthemum ‘Brandywine Sunset’

Chrysanthemum ‘Autumn Bronze’

 

Hardy garden mums are uncommonly grown in the Upper Midwest, so their value as late-season garden plants here was uncertain at the outset of the trial. The late bloom extends the season for gardeners and pollinators but presents a problem in colder climates where average frost dates occur earlier and weather is increasingly unpredictable. Growing the garden mums over multiple seasons provided information on the ornamental potential of their floral display—flower production and length of the bloom period—related to autumnal frost dates. Additionally, determining their real cold-hardiness was important. 

The primary goal was to evaluate garden mums, often referred to as old-fashioned mums, rather than the more commonly available seasonal mums, although three landscape mums were included. Nearly half of the mums received excellent or good overall final ratings, with ‘Autumn Spice Igloo’ and ‘Hillside Sheffield Pink’ earning top scores for strong flower production, habit quality, and winter hardiness. While a comprehensive evaluation was undertaken, the floral show was the primary ornamental trait contributing to the overall ratings. Plant habit quality and winter hardiness were also factored into the final scores. Generally, winter hardiness was not deemed a problem for the mums in the trial. Fewer than 10 percent of the plants died over the four-year trial period. 

The late-blooming flowers might be considered a significant drawback to growing perennial mums in cold climate zones; however, heavy flower production ensured a strong floral display even when bloom periods were shortened by frosts. Mid-October was the latest start of flowering and November 9 was the latest hard frost date recorded between 2021 and 2025. Copious flowers were still blooming on some of the mums when frost occurred. While a shortened flower period is not ideal, the quality, quantity, and novelty of the colorful garden mums will be worth it for some gardeners.