Thuja L.

Thuja is a small genus of five to six more or less closely related species. In addition to the species below, at least one other taxon is regularly cultivated in Belgium: T. orientalis L. (currently accommodated in a separate genus as Platycladus orientalis (L.) Franco), a native of Asia. It might escape as well and is the least rare species of Thuja in parts of Germany (Adolphi 1995). Thuja orientalis is characterised by almost scentless leaves (even when crushed), branchlets flattened in vertical planes (vs. horizontal planes) and the seeds are wingless (vs. winged).

Juvenile plants of Thuja are usually hardly identifiable in the absence of obvious parental trees.

In general, Thuja seems to reproduce more rarely than Chamaecyparis in Belgium.

  • Upper side of facial scale leaves with a conspicuous, raised gland. Scale leaves not whitish-green beneath when fresh. Branches usually strongly flattened === 1. Thuja occidentalis
  • Upper side of facial scale leaves usually without a raised gland (gland very rarely present, but then inconspicuous and never raised). Scale leaves whitish-green beneath when fresh. Branches less flattened or not flattened at all === 2. T. plicata



Adolphi K. (1995) Neophytische Kultur- und Anbaupflanzen als Kulturflüchtlinge des Rheinlandes. Nardus 2: 1-272.

Chambers K.L. (1993) Thuja. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 2. Oxford University Press, New York-Oxford: 410-411.

Christensen K.I. (2000) Coniferopsida. In: Jonsell B. (ed.), Flora Nordica, vol. 1. The Bergius Foundation, Stockholm: 91-115.

De Koning J., Van den Broek J.W., Van de Laar H.J. & Fortgens G. (2000) Nederlandse dendrologie (13e druk). H. Veenman & zonen, Ede: 585 p.

Lewis J. (1986b) Thuja. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 1. Cambridge University Press, Cambridge: 80.

Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.

Sun B. et al. (2015) Recognizing the species of Thuja (Cupressaceae) based on their cone and foliage morphology. Phytotaxa 219(2): 101-117.

Taxonomic name: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith