Week 19: Sheet Moss, Hildegard von Bingen, Michael Marder

Cover Image. “Plate XXXIII. HYPNEAE (continued),” from F.E. Tripp, British Mosses: Their Homes, Aspects, Structure, and Uses, Vol. II (London: George Bell and Sons, 1874).

The month of May began with a full moon, marking the first time since 1988 that the cross-quarter day of May 1 aligned with the peak or midpoint of the lunar cycle.

Headnote

If there’s a plant that reminds me of God, it’s probably moss. Indeed, the plant’s biology is as ornate and rarefied as any systematic theology. Ubiquitous and abundant but amorphously changing, obvious but mysterious, perennially surprising and yet easy to take for granted, expanding or contracting as it slowly transforms its surroundings—modest moss can be as soft as the tender, mighty mullein, but its diminutive, hair-like roots, called rhizoids, work over time to accomplish feats of erosion that would be impossible for other plants. Moss is slow green fire, breathing air, water, and minerals into its pseudoparts; and permitting a multitude of traditional and experimental applications, from bedding, wound-dressing, and whiskey-making to biofuels and pharmaceuticals. For example, because of their nearly immediate interchange with the atmosphere, these subtle sculptors also function as bioindicators in both wild and human-developed landscapes, reflecting the quality of the air and capable of detecting even microplastics and trace elements of heavy metals.

The full-spectrum greens of the mosses embody the viriditas (“greening power” or “greening life-force”) that medieval mystic Hildegard of Bingen identified as God’s vital presence suffusing earth, soul, and cosmos. In her dynamic elemental visions, consuming-illuminating fire and blowing-atmospheric wind converge to draw moisture into dry soils, bodies, and souls, bringing forth plants and fruits, growth and strength, virtuous acts of faith and hymns of praise. Although May and its first day are conventionally a time of flowers—the Roman festival of Floralia, the circling garlands and symbols of the maypole, and the month of Floréal on the French Revolutionary calendar—for me this is a month of mosses. Look to the decaying ground and the rocky crevices for a soft brush with the Creator.

The Hypnum genus, classified in the Hypnales order of “leafy” or “feather” mosses, is known for its thick, carpet-like growth and vivid green, yellow, or brown colors. These branching, mat- and tuft-forming species are pleurocarpous (pleura, “side,” plus karpos, “fruit”), in contrast to upright, capsule-bearing acrocarpous varieties. The Hypnum genus includes an undetermined number of species (in the range of hundreds), but all are part of the 11,000+ “true mosses” in the class Bryopsida. This class excludes several hundred varieties of moss (e.g., peat and granite mosses), which have various distinct characteristics, as well as outright imposters such as Spanish moss (related to the pineapple) and Irish moss (a seaweed). Along with liverworts (Hepaticopsida) and hornworts (Anthocerotophyta). All mosses are bryophytes in the Bryophyta division. These non-vascular, moisture-dependent plants lack true roots, stems, and leaves but are crucial for soil development and water retention. And the Victorians sure did love to press them under magnifying glasses.

Fig. 1. “Mosses,” from A.J. Grout, A. J. Mosses With Hand-lens And Microscope: a Non-technical Hand-book of the More Common Mosses of the Northeastern United States, illus. Mary V. Thayer (New York: Self-published, 1900), p. 37.

Readings

1. How could any creation of Mine be void and useless? For every creature that lives (even those without the powers of reason or sensation) has two useful properties within itself, and one that perishes. The two useful ones are its juiciness or sap and its green foliage, but the other part withers in its dryness. The human being also has two components, that is, the soul and the body— the soul in virtues, the body in action— but it also knows evil, which is arid like the part that perishes.

Hildegard of Bingen, “334. Letter to Secular People” (circa 1153), Letters of Hildegard of Bingen: Volume 3 (New York: Oxford University Press, 2004), p. 136.

2. Why is our conceptualization of time, drawing on metaphysical order and stability, ineffectual when it comes to the time of moss? First, as we have seen, the relative terms young and old, before and after, are inapplicable there where a linear chronology breaks down. Second, the paradigm of energy gradually dissipating in the measure of distancing from an energetically rich beginning no longer works when faced with moss: diminished vitality coincides with the exuberance of mossy vegetal life, one that infinitely mirrors and is mirrored in “the architecture of the forest.” Third, though “primitive,” moss encompasses at least fourteen thousand species and includes virtually all methods of plant reproduction (be they sexual or asexual) and growth, reliant on mutual interactions with the boundary layer or the microclimate that surrounds each leaf and growing point of every plant. Hence, already, in the nineteenth century, a relevant entry in The Edinburgh Encyclopedia stated: “He who could examine the nutrition, the growth, the regular confirmation, the provision made for the continuation of the species…of even the minutest Phascum [mosses], without perceiving in them proofs of intelligence, power, and goodness, would probably receive no more conviction from the sublimest truths that astronomy can unfold.” Finally, moss grinds rocks to stand and builds up soil for future plant growth; it performs simultaneously the tasks of analysis and synthesis, complicating the (mythical) image of time as a universal destroyer, the merciless devourer of all without exception.

Michal Marder and Edward S. Casey, Plants in Place: A Phenomenology of the Vegetal (New York: Columbia University Press, 2024), p. 76.

3. Along with lichens, bryophytes are often the first actors in primary succession: the ecological process of weathering bare rock into soils that can sustain more complex forms of life. This can occur after a volcanic eruption or the retreat of a glacier; here in New England, mosses and lichens are still waging a battle against the bare rock of our highest peaks. Once established, bryophytes modify their environment through cation exchange. In this process, a bryophyte releases a proton (H+) from its cell walls into the surrounding environment, which in turn displaces positively charged ions (cations) such as calcium (Ca²⁺), magnesium (Mg²⁺), and potassium (K⁺) from nearby soil or rock particles. The bryophyte then absorbs these essential nutrients into its tissues.

“Mosses of Maine: A Brief Guide,” Oxford County CTS (October 15, 2025).

Supplementum

• “O Nobilissima Viriditas,” text by Hildegard von Bingen, composed/arranged by Bryce Dressner, featuring Barbara Hannigan, David Chalmin, and Katia Labèque, and Marielle Labèque. Electric Fields (Alpha Classics, 2025).

• Text of “O Nobilissima Viriditas,” International Society of Hildegard von Bingen Studies (April 21, 2017).

• Bruce McCune and Kristen Whitbeck, “Living in the Land of Mosses,” Pacific Northwest Pest Management Handbooks (March 2023).

• Ellen McHale, “7 Interesting Things About Mosses,” Kew Royal Botanic Gardens (May 23, 2020).

• The Bryophyte Nomenclator. ed. John C. Brinda and John J. Atwood (April 2026).

Fig. 2. “O Nobilissima Viriditas,” text by Hildegard von Bingen, composed/arranged by Bryce Dressner, featuring Barbara Hannigan, David Chalmin, and Katia Labèque, and Marielle Labèque. Electric Fields (Alpha Classics, 2025).