Thuja

Linnaeus

Sp. Pl. 2: 1002. 1753; Gen. Pl. ed. 5, 435, 1754.

Common names: Arborvitae thuya cèdre
Etymology: Greek name for some evergreen, resinous trees
Treatment appears in FNA Volume 2.

Trees evergreen, small to large. Branchlets flattened, in fan-shaped, flattened, frondlike sprays. Leaves opposite in 4 ranks. Adult leaves heteromorphic; those on larger branchlets with sharp, erect, free apices to ca. 2 mm; those on flattened lateral branchlets crowded, appressed, scalelike, lateral pairs keeled, facial pairs flat; abaxial glands present or absent. Pollen cones with 2–6 pairs of sporophylls, each sporophyll with 2–4 pollen-sacs. Seed-cones maturing and opening first-year, ellipsoid, (6–) 9–14 (–18) mm; scales persistent, 4–6 pairs, overlapping, oblong and basifixed, thin and woody, 2–3 central pairs fertile, uniformly thin or with slightly enlarged apex, remaining scales sterile. Seeds 1–3 per scale, lenticular, equally 2-winged; cotyledons 2. x = 11.

Distribution

North America, e Asia

Discussion

Two Asiatic species, Thuja koraiensis Nakai (Korean arborvitae) and T. standishii (Gordon) Carrière (Japanese arborvitae), are occasional in cultivation. They differ from the native species in having more closely spaced long-shoot leaves with shorter, spreading points.

Species 5 (2 in the flora).

Selected References

None.

Key

1 Foliage dull yellowish green abaxially and adaxially; seed-cone scales minutely mucronate; e United States and e Canada. Thuja occidentalis
1 Foliage white-striped abaxially when fresh, glossy green adaxially; seed-cone scales with evident, nearly terminal, deltate projection; w United States and w Canada. Thuja plicata
... more about "Thuja"
enlarged +
0 cm0 mm <br />0 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
Kenton L. Chambers +
Linnaeus +
long-lived +
inconspicuous +  and undifferentiated +
Arborvitae +, thuya +  and cèdre +
North America +  and e Asia +
Greek name for some evergreen, resinous trees +
scale-like +  and flattened +
decurrent +  and scale-like +
heteromorphic +
persisting +
3 (?) +  and 5 (?) +
0 cm0 mm <br />0 m <br /> (1 cm10 mm <br />0.01 m <br />) +
spheric;oblong +
fibrous;woody +
peltate +  and complex +
cuneate +  and oblong +
fleshy +  and woody +
overlapping +
persistent +
basifixed +
sterile +  and fertile +
with slightly enlarged apex +  and thin +
1 +  and 2 +
1 +  and 3 +
lenticular +
frondlike +, flattened +  and fan--shaped +
Cupressaceae +
flattened +, angled +  and terete +
small +  and large +
asymmetric +  and symmetric +