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Tree Campus: St. John’s Wort

Tree Campus SCC is a multi-year and interdisciplinary college initiative to document, map, and celebrate the incredible diversity of trees planted on the campus. With over 200 species, Shoreline Community College is an arboreal paradise that deserves to b


St. John’s Wort

Hypericum calycinum (HYPERICACEAE)



S. Europe, S.W. Asia



"Many flowers have UV patterns, invisible to humans but visible to insects such as honeybees, whose visual sensitivity extends into the near UV region of the solar spectrum. These patterns are part of the visual gestalt of the flower and as such are meaningful to the pollinator... in addition to displaying a conventional UV bull’s-eye pattern on the facial surface, [H. calycinum] exhibited a rare trait... the possession of UV markings on the abaxial surface...

In Jasminium primulinum... the phenomenon is a consequence of differential UV demarcation of those petal parts exposed to the outside in the unopened bud. Whereas these exposed parts are UV-absorbent, the petal portions hidden in the bud that come into view only at maturity in the open blossom are UV-reflectant. Buds, as a result, are kept different in appearance from the mature flowers, to the potential benefit of plant and pollinator alike, because the open flowers are thereby unambiguously advertised...

In Hypericum edisonianum... the petals overlap in accord with a fixed pattern (imbricate aestivation). As a result of such overlap, the petals, on their reverse surface, are precisely divided into a UV-absorbent zone, exposed in the bud, and a reflectant zone, exposed in the blossom.

H. calycinum [showed] the same UV characteristics as H. edisonianum... UV pigments [were] present in all UV-absorbing parts of the flower but unexpectedly found the DIPs to be deposited at extraordinarily high concentration in the ovarian wall. This observation raised the possibility that these compounds also served as antifeedants, possibly for protection of the developing seeds against insect herbivores. We found [dearomatized isoprenylated phloroglucinols (DIPs)] also to be concentrated in the anthers, indicating that they might protect the pollen as well. Tests that we undertook with a caterpillar and one of the DIPs... showed this compound to be not only deterrent but also toxic to the insect, thereby underscoring the possibility that DIPs serve in defense." [1]


Equity: Cultural and Historical Significance

"This plant is a common ornamental, native to Southeastern Europe." [1]



"Two categories of pigments, flavonoids and dearomatized isoprenylated phloroglucinols (DIPs), are responsible for the UV demarcations of this flower... The DIPs of hops are put to human use as bitter flavoring agents and preservatives in beer." [1]



[1] Gronquist, M., Bezzerides, A., Attygalle, A., Meinwald, J., Eisner, M., & Eisner, T. (2001). Attractive and defensive functions of the ultraviolet pigments of a flower (Hypericum calycinum). Proceedings of the National Academy of Sciences, 98(24), 13745-13750.

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