2 responses to “February in the Garden 2023”

  1. Garden Communications

    Hi Ron, I reached out to Douglas Justice and shared your blog post response and he has replied to you here:

    Regarding the junipers in this article, we have a number of wild-sourced Juniperus communis plants in the garden with a variety of names attached. Their taxonomy has been neglected for years (and I admit to putting off doing my homework here). This is a confusing group and there is much in the literature that is confused and misleading with respect to naming. For example, there is only partial agreement between Flora of North America and Plants of the World Online. A thorough review is clearly in order.

    Regarding the cypresses, I would definitely prefer to be using the classification outlined on D. Earle’s page (https://www.conifers.org/cu/Cupressus.php), as it is straightforward and appears eminently sensible. Unfortunately, it’s not based on the most up-to-date research. The need to split the group follows a 2022 paper (see Recent advances on phylogenomics of gymnosperms and a new classification, by Yong Yang et al., Plant Diversity 44 (2022) 340-350), which pretty much upsets the whole Cupressus apple cart.

    The Yang et al. paper reveals that Cupressus as traditionally circumscribed is actually represented by two distinct clades (branches) on the family tree: a Eurasian-African clade with about eight species, and a western (strictly North American) clade (Hesperocyparis) with about a dozen species. Uniting them all under one broadly-defined Cupressus was not possible once it was also discovered that the Eurasian-African branch is more closely related to Juniperus than to Hesperocyparis, while Hesperocyparis is more closely related to Callitropsis nootkatensis (yellow cedar) and Xanthocyparis vietnamensis (Vietnam yellow cedar) than it is to the Old-World cypresses. The alternative (if one is to maintain monophylly) is to lump all of the species, including Juniperus, into one genus. I would happily recant if someone proves that the work by Yang et al. is flawed.

    Here is the relevant passage from the paper:

    2.5. Relationships of the Callitropsis-Cupressus-Hesperocyparise-Xanthocyparis complex
    Farjon and his collaborators described a new genus collected from Vietnam, i.e., Xanthocyparis Farjon & T.H. Nguyen (Farjon et al., 2002). The nomenclature of this genus and subsequent molecular systematic studies resulted in debates and taxonomic chaos within Cupressus L. and related genera (Farjon et al., 2002; Little, 2006; de Laubenfels, 2009; Zhu et al., 2018). Farjon et al. (2002) included Callitropsis Oerst. in the genus Xanthocyparis, i.e., Xanthocyparis nootkatensis (D. Don) Farjon & Harder. This inclusion made the name Xanthocyparis superfluous and illegitimate in nomenclature. For further use of Xanthocyparis, Mill and Farjon (2006) proposed to conserve Xanthocyparis against Callitropsis, and the nomenclature committee accepted their proposal (Brummitt, 2007). Little (2006) constructed a phylogeny of Xanthocyparis, Callitropsis, and Cupressus s.s., and found that Cupressus is diphyletic; he thus treated Xanthocyparis, Callitropsis and the New World Cupressus as a single genus. He adopted Callitropsis s.l. as the correct generic name and made a number of new combinations. But phylogenetic relationships among these generic clades were not resolved in that study. Christenhusz et al. (2011) took a conservative option and incorporated Xanthocyparis, Callitropsis, and Hesperocyparis Bartel & R.A. Price into Cupressus, which is paraphyletic with respect to Juniperus (Mao et al., 2019). Terry et al. (2012), Zhu et al. (2018), and Mao et al. (2019) resolved the phylogenetic relationships of these genera and recognized Xanthocyparis s.s., Callitropsis s.s., Hesperocyparis (New World Cupressus) and Cupressus s.s. (Old World Cupressus). Callitropsis s.s. and Xanthocyparis s.s. do not form a clade in these recent phylogenies; thus, Farjon’s incorporation of Callitropsis s.s. into Xanthocyparis s.l. is untenable.

  2. Ron Brightman

    See discussion of Cupressus taxonomy here:


    Dr. Earle has also produced an updated treatment of Juniperus communis, see his page on this species on the same web site.

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