Anthocyanin Hyperexpression (“Melanism”) in Pacific Northwest Lily Populations

Anthocyanin Hyperexpression (“Melanism”) in Pacific Northwest Lily Populations

By Bret Hansen

“Melanism” is a term most people associate with animals, images of black jaguars, black leopards, and other mammals whose appearance is shaped by the overproduction of melanin. Yet in the plant world, a similar visual effect occurs, though driven by different pigments and biochemical pathways. In the Pacific Northwest, several populations of native lilies exhibit remarkably dark, heavily pigmented flowers that resemble animal melanism in their depth of color. These flowers showcase a form of anthocyanin hyperexpression, sometimes so pronounced that the tepals appear almost black. This article describes three of these rare populations, considers the evolutionary advantages of such pigmentation, and emphasizes their significance as unique and vulnerable genetic lineages.

In animals, melanism arises from an excess of melanin, while pseudomelanism refers to enlarged spot or stripe patterns that give the impression of overall darkness without being fully black. Plants also produce melanin, like pigments, but their chemistry differs from that of animals. Anthocyanins are the dominant floral pigments responsible for red, purple, and blue coloration in many tissues, and their accumulation often increases under environmental stress, where they provide photoprotection and antioxidant defense (Gould 2004; Mannino et al. 2021; Dabravolski et al. 2023).

Plants also produce allomelanins—heterogeneous, nitrogen-free polymers found largely in seed coats, where they contribute to UV screening, pathogen resistance, and mechanical strength (Glagoleva, Shoeva, and Khlestkina 2020).

The confusion arises because the visual result of anthocyanin hyperexpression in flowers can mimic animal melanism, even though the underlying pigments are chemically distinct. Famed lily geneticist and breeder Judith Freeman of the Lily Garden suggested that “Variation in Anthocyanins in Lilies” might be a more accurate title than invoking the word 'melanism', and she is correct from a botanical standpoint. Nevertheless, the visual analogy is a useful one, especially for describing the depth and coverage of pigment seen in these unusual lilies.

Why such dark pigmentation arises in plants is still not entirely clear. Pigmentation in flowers is certainly influenced by pollinator selection, shaping colors, patterns, and fragrances to appeal to specific pollinators, but heavy pigmentation, especially when it spreads from discrete spots to near-full tepal coverage, may provide additional advantages beyond simple attraction. A substantial body of work suggests that anthocyanins act as what Kevin Gould has called “nature’s Swiss army knife,” buffering plants against high light, ultraviolet radiation, and photooxidative stress, while also playing roles in resistance to drought, cold, heavy metals, and biotic attack (Gould 2004; Wang 2019; Mannino et al. 2021).

Dark surfaces absorb more solar energy and can warm more quickly in the cool mornings typical of the Pacific Northwest, enabling earlier nectar production, improved pollen viability, and faster seed maturation. Studies in crop plants have shown that dark or anthocyanin-rich tissues and seeds often germinate earlier and exhibit improved vigor under stress, including nutrient limitation and drought (Liang and He 2018; Dabravolski et al. 2023).

Anthocyanins and melanin-like pigments also provide strong protection against ultraviolet radiation, safeguarding delicate floral tissues and protecting DNA from UV-induced damage (Gould 2004; Mannino et al. 2021).

Their antioxidant properties contribute further resilience during heat or oxidative stress, and plants with heavier pigmentation often show improved resistance to fungal pathogens. Dark pigmentation may also aid in avoiding herbivory. Many herbivores and seed predators rely on contrast rather than fine color discrimination; darker flowers and seeds can blend more easily into shadowed understory, forest duff, or dark volcanic soils, reducing their visibility against the background. At the same time, pollinators such as hummingbirds, swallowtails, and certain moths perceive ultraviolet patterns and fluorescence beyond the human visual spectrum. A flower that appears almost black to us may, under UV light, display bright nectar guides and contrasting patterns that remain perfectly obvious to a pollinator. In that sense, hyperpigmented flowers may be cryptic to herbivores yet fully visible—or even enhanced—to the animals that matter most for reproduction.

The first example of this phenomenon is the Lilium columbianum form known as the “Mirro” population, named for Gene Mirro, who first documented it in the Columbia River Gorge. In typical L. columbianum, anthocyanins appear as scattered purple spotting on golden-orange tepals. In the Mirro form, however, these spots expand dramatically, merging into broad swaths of dark pigmentation until much of the tepal surface is deeply colored. Within the population, the phenotype ranges from partial expression with enlarged spotting to nearly solid dark tepals, suggesting a heritable trait with variable penetrance. Red buds are another distinctive feature—unusual for a species whose buds are normally yellow to orange. Another interesting characteristic of this strain is the deep red buds. Typical columbianum has orange buds. The 'Mirro' strain has bright red buds, which make it easy to identify when not in bloom and buds are developing.

To current knowledge, this Mirro population represents the only stable breeding population of its kind, making it a uniquely valuable and irreplaceable genetic lineage that merits serious conservation attention.

A second example is found in Lilium occidentale, one of the rarest lilies in the world. During a family lily-hunting trip along the Pacific coast, I quiet accidentally discovered a population of L. occidentale containing several heavily spotted individuals and, remarkably, one fully melanistic plant with inner tepals so dark they appeared nearly black, hence the informal name “Black Throat.” We had pulled off the road so I could converse with nature. Long story short, I noticed what looked like lily stems in a clearing just off the road in a wet aera. Reaching the plants required navigating blackberry tangles, coastal brush, standing water, and a dense cloud of mosquitoes, but the stand itself was spectacular: tall, vigorous, and floriferous, with some stems reaching six to seven feet and bearing dozens of flowers. In this population I discovered a single stem with a dozen or so flowers that appeared to express a similar color pattern as the 'Mirro' L. columbianum only they were more than 200 miles (360km) apart. I wish I would have stayed longer and gotten more pictures but I was being eaten alive by the mosquitoes.

Whether the melanistic form persists there today remains unknown, as habitat loss and human disturbance have devastated many L. occidentale populations. Given that L. occidentale already occupies a narrow ecological niche and is under intense anthropogenic pressure, any unusual genotype within the species, particularly one affecting flower morphology and pigment, warrants heightened interest and protection.

The third case is a striking Lilium columbianum population discovered by the late Eddie McRae near Parkdale and Dee, Oregon. Eddie had showed me a stand of tall 4-5 foot plants right off the side of the road bearing flowers so heavily pigmented that they appeared almost entirely black except for narrow orange margins at the petal edges. It was the most dramatic dark phenotype I have ever seen in the species. This was before smartphones so I didn't get any pictures. Unfortunately, the site has not been revisited in many years, and the population’s current status is unknown. In the dense conifer forests of the Mount Hood region, it is entirely possible for dark flowers to blend so effectively into the background that even an experienced lily hunter, or a hungry deer, can walk right past them. It is equally possible that roadside maintenance, development, or successional overgrowth have erased the population altogether.

These observations strongly suggest a heritable basis for dark pigmentation in these populations, with expression patterns consistent with either recessive traits, incomplete dominance, or the involvement of multiple alleles. Because floral morphology is intimately bound to pollinator behavior, the continued presence of these traits in the population implies that they are either beneficial or at least not harmful to pollinator attraction. Their persistence also resonates with experimental work in model plants, where mutations in regulatory genes and stress-signaling pathways can drive anthocyanin hyper-accumulation and deep red or purple phenotypes in leaves, stems, and seeds (Liang and He 2018; Wang 2019; Mannino et al. 2021).

In that broader context, the Mirro, McRae, and “Black Throat” lilies appear not as inexplicable curiosities, but as wild expressions of pigment pathways that we know are sensitive to environment, stress, and selection.

The conservation significance of these dark forms cannot be overstated. They represent unique genetic resources, localized evolutionary experiments not found anywhere else in the world. Losing these populations would mean more than losing beautiful flowers; it would mean the extinction of entire genetic lineages and adaptive possibilities within the genus Lilium. The Pacific Northwest is home to extraordinary lily diversity shaped by fire cycles, microhabitats, and complex ecological pressures. Protecting these rare pigmented forms helps safeguard not only individual plants, but also the broader evolutionary tapestry to which they belong. In the face of habitat loss, climate change, and ongoing disturbance, documenting, monitoring, and, where possible, affording legal protection to such populations should be considered part of responsible stewardship.

Melanistic or hyper-anthocyanin lilies are rare, beautiful, and scientifically valuable. They challenge our assumptions about plant pigmentation, raise compelling questions about adaptation, and highlight the stakes of habitat loss in a rapidly changing world. While much remains to be understood about why these mutations arise and how they persist, documenting and protecting them is an essential step toward preserving the natural heritage and evolutionary richness of the Pacific Northwest and its wild lilies.

Safety Note for Lily Hunters

Fieldwork in search of wild lilies is rewarding, but it can also be unexpectedly dangerous. While following advice from the legendary Boyd Kline of Medford, Oregon, I once went looking for Lilium occidentale in a remote coastal wetland. Boyd had told me where he’d seen them some thirty years earlier—in the 1970s—and as usual, he was exactly right. We found the lilies growing precisely where he said they’d be. What we didn’t expect was the large patch of marijuana growing around us.

Remote, wet forest clearings in the Pacific Northwest are ideal locations for illegal grow sites, and stumbling into one is not a pleasant experience. We took a few quick photographs of the lilies and left immediately. That wasn’t the only time I’ve had a close call. I’ve been chased by my share of black bears while bushwhacking through dense forest in search of lilies. just outside Cresent City, California, agian searching for L. occidentale, we encountered a large homeless encampment in a wet boggy area. I’ve learned that the combination of rugged terrain, poor visibility, and wildlife, and people makes lily hunting more of an adventure than most people suspect.

If you’re heading into the woods looking for lilies, caution is essential. Always be aware of your surroundings, pay attention to where you step, and know when to turn back. No rare lily is worth a confrontation with drug growers, startled wildlife, property owners, or homeless people, or the other hazards that lurk in thick Pacific Northwest brush. Situational awareness is your best friend; curiosity is good, but coming home safely is better.

Suggested reference list

Gould, Kevin S. 2004. “Nature’s Swiss Army Knife: The Diverse Protective Roles of Anthocyanins in Leaves.” Journal of Biomedicine and Biotechnology 2004: 314–320.

Glagoleva, Anastasiya Y., Olesya Y. Shoeva, and Elena K. Khlestkina. 2020. “Melanin Pigment in Plants: Current Knowledge and Future Perspectives.” Frontiers in Plant Science 11: 770. https://doi.org/10.3389/fpls.2020.00770

Liang, Junli, and Jian-Yuan He. 2018. “Protective Role of Anthocyanins in Plants under Low Nitrogen Stress.” Biochemical and Biophysical Research Communications 498 (3): 946–953.

Mannino, Giuseppe, Cristina Gentile, Sergio Emanuele Radice, Alessandra M. Bertea, and others. 2021. “Anthocyanins: Biosynthesis, Distribution, Ecological Role, and Use of Biostimulants to Increase Their Content in Plant Foods—A Review.” Agriculture 11 (3): 212.

Wang, Hongxue. 2019. “Research Advances in the Function of Anthocyanin in Plant Resistance to Stress.” Acta Agriculturae Zhejiangensis 31 (1): 137–148.

Dabravolski, Sergey A., Andrea J. Kavalionak, Karolina P. Isayenkova, and others. 2023. “The Role of Anthocyanins in Plant Tolerance to Drought Stress.” Plants 12 (13): 2