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Diphasiastrum tristachyum — blue ground-cedar

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Facts

The branches of blue ground-cedar have a distinctive blue-green color due to the bloom on its surfaces. This species can hybridize with all the other ground-cedar (Diphasiastrum) species in New England.

Habitat

Anthropogenic (man-made or disturbed habitats), forest edges, forests, meadows and fields, woodlands

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf shape
the vegetative leaves are short and scale-like
Spore leaf arrangement
the sporophylls are located on spore cones at the tips of the shoots or branches
Form of shoot
the plant has an upright stem, with branches, those branches having further branches, and so on (tree-like)
Horizontal stem
the horizontal stem is under ground
Leaf differences
the vegetative leaves within a node differ in size and shape
Teeth on leaf edges
the edges of the vegetative leaves have no teeth
Spore leaf length
2.2–3.5 mm
Leaf outline
the vegetative leaves are roughly triangular, widest at the base where the leaf joins the stem
Show all characteristics

  • Clonal plantlets

    Gemma arrangement
    NA
    Gemma shape
    NA
    Gemma width
    0 mm

  • Leaves

    Leaf differences
    the vegetative leaves within a node differ in size and shape
    Leaf length
    1–7.2 mm
    Leaf orientation
    • the vegetative leaves are pressed against the stem
    • the vegetative leaves spread slightly away from the stem, at a steep angle
    Leaf outline
    the vegetative leaves are roughly triangular, widest at the base where the leaf joins the stem
    Leaf ranks
    4
    Leaf shape
    the vegetative leaves are short and scale-like
    Pores on leaves
    there are pores, but only on the underside of the vegetative leaves
    Spore leaf length
    2.2–3.5 mm
    Teeth on leaf edges
    the edges of the vegetative leaves have no teeth

  • Place

    Habitat
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • edges of forests
    • forests
    • man-made or disturbed habitats
    • meadows or fields
    • woodlands

  • Spores or spore cones

    Cone base at stem
    the base of the spore-cone has a distinct stalk
    Cone stalk branching
    the stalks bearing the spore cones are branched, with pairs of branches
    Cone thickness
    0.4–1 mm
    Cone width
    2–3 mm
    Length of cone
    10–24 mm
    Number of cones
    2–4
    Quillwort itssue covering spores
    NA
    Same or different spores
    there is only one type of spore present
    Spore girdle
    NA
    Spore leaf arrangement
    the sporophylls are located on spore cones at the tips of the shoots or branches
    Spore leaf lifespan
    the sporophylls wither and fall off at the end of the growing season
    Spore leaf orientation
    the sporophylls are pressed against the spore cone
    Spore leaf shape
    the spore-bearing leaves are small and scale-like
    Spore leaf teeth
    The edges of the spore-bearing leaves are smooth, and without teeth
    Spore texture
    the spore surface has a net-like pattern on it (reticulate)
    Sterile tip of cone
    the spore cone does not have a slender, sterile tip (the whole cone produces spores)

  • Stem, shoot, branch

    Branch cross-section
    the outermost level of branches are approximately square in cross-section
    Branch form
    the branches are smaller than the main stem
    Constriction zones
    • there are constricted zones on the horizontal stem where the leaves are smaller smaller or closer together
    • there are constricted zones on the vertical stem where the leaves are smaller smaller or closer together
    Form of shoot
    the plant has an upright stem, with branches, those branches having further branches, and so on (tree-like)
    Horizontal stem
    the horizontal stem is under ground
    Horizontal stem thickness
    1.5–3.2 mm
    Stem height
    170–360 mm

Wetland status

Not classified

In New England

Distribution

Connecticut
present
Maine
present
Massachusetts
present
New Hampshire
present
Rhode Island
present
Vermont
present

Conservation status

Exact status definitions can vary from state to state. For details, please check with your state.

Massachusetts
widespread (S-rank: S5)

From Flora Novae Angliae dichotomous key

4.  Diphasiastrum tristachyum (Pursh) Holub N

blue ground-cedar. Diphasium tristachyum (Pursh) Rothm.; Lycopodium chamaecyparissus
A. Br. ex Mutel; L. tristachyum Pursh • CT, MA, ME, NH, RI, VT; throughout. Dry-mesic to xeric, often acid, soils of woodlands, forests, edges, and openings. Diphasiastrum tristachyum is involved in more hybrid combinations than any other Diphasiastrum in New England.

1×4. Diphasiastrum complanatum × Diphasiastrum tristachyum → Diphasiastrum ×‌zeilleri (Rouy) Holub is a rare ground-cedar hybrid known 
from ME, NH, VT. It is intermediate between its parents in branch width, number of times 
the branches divide, and relative size of the trophophylls of the lower rank.

1×Diphasiastrum alpinum (L.) Holub. Diphasiastrum ×‌issleri (Rouy) Holub is 
a very rare ground-cedar hybrid in New England known only from northern ME. It 
generally resembles D. complanatum except that its lateral trophophylls usually roll under the branch (i.e., the branch margin is revolute) and the base of its strobilus 
is not distinct (i.e., there is a gradual transition from strobilus stalk trophophylls to strobilus sporophylls).

2×4. Diphasiastrum digitatum × Diphasiastrum tristachyum → Diphasiastrum ×‌habereri (House) Holub is an infrequent ground-cedar hybrid known from MA, ME, NH, VT. It has winter bud constrictions on the lateral branches, similar to D. tristachyum, but is otherwise intermediate in branch width, relative size of trophophylls of the lower rank, and strobilus stalk branching.

3×4. Diphasiastrum sitchense × Diphasiastrum tristachyum → Diphasiastrum ×‌sabinifolium (Willd.) Holub is a somewhat rare but widespread ground-cedar hybrid known from ME, NH, VT that frequently occurs in the absence of its parents. It has somewhat compressed lateral branches with 4 ranks of trophophylls that are adnate to the branches 50–60% of their length (most species, except D. sitchense, 
with trophophylls adnate more than 60% of their length), and shows a gradual transition from stobilus stalk trophophylls to strobilus sporophylls.

Native to North America?

Yes

Sometimes confused with

Diphasiastrum digitatum:
branches rectangular in cross-section, 2 mm wide or wider, usually without winter bud constrictions, and horizontal shoots at or near the surface (vs. D. tristachyum, with branches square in cross-section, as wide as 2 mm, with winter bud constrictions, and horizontal shoot buried deeper than 5 cm).

Synonyms

  • Diphasium tristachyum (Pursh) Rothm.
  • Lycopodium chamaecyparissus A. Br. ex Mutel
  • Lycopodium tristachyum Pursh

Family

Lycopodiaceae

Genus

Diphasiastrum