Physiognomy and Structure: This group contains tall coastal temperate rainforests 20 to >35 m tall, dominated by evergreen conifer trees. Undergrowth canopy varies from thick to sparse depending on site productivity and overstory canopy closure.

Floristics: Overstory canopy is dominated by Pseudotsuga menziesii with Tsuga heterophylla and/or Thuja plicata. Pseudotsuga menziesii is usually at least present to more typically codominant or dominant. Acer macrophyllum and Alnus rubra sometimes be present in the subcanopy. Stands occur on dry well-drained as well as subirrigated soils. Dry-site understory shrubs typically include Gaultheria shallon, Mahonia nervosa, Rhododendron macrophyllum (but not in British Columbia), Linnaea borealis, and Achlys triphylla. Intermediate moisture (mesic) locations often have Acer circinatum and Polystichum munitum (especially on rich-nutrient sites) with one or more of the evergreen shrubs. Moist sites are dominated by Polystichum munitum, Oxalis oregana, Rubus spectabilis, and/or Oplopanax horridus. Indicator species include Tsuga heterophylla and Pseudotsuga menziesii with a lack (or very low amounts) of Abies amabilis. Understory indicator species include Polystichum munitum, Achlys triphylla, Gaultheria shallon, and Vaccinium parvifolium; in other words, stands without Picea sitchensis in the tree canopy and lacking understory indicator species more common near the coast, such as Blechnum spicant, Anemone deltoidea, Maianthemum dilatatum, and Vaccinium ovatum, as well as without wetland indicator species, such as Lysichiton americanus.

Dynamics:  Stands originated from infrequent stand-replacing fires (perhaps every 150-200 years) that would occur only in the driest microsites, as well as from windthrow gaps. Stand-maintaining surface fires, both aboriginal and lightning-caused, were more frequent (perhaps every 50-100 years) (Agee 1993, Brown and Hebda 1999) prior to European settlement. Surface fires likely maintained a moderately open overstory. Gap dynamics in old forests result in multi-aged stand structure (BCCDC unpubl. data 2013). Unless growing in wind-protected conditions, windthrow and breakage tend to keep these forests from becoming or remaining very old. Tsuga heterophylla, one of the leading tree species, is vulnerable to wind breakage and also to uprooting given the shallow soils. If wind exposure is limited, then stand replacement is more gradual, through the process of the mortality of individuals or small numbers of canopy trees. Where windthrow is not pervasive, the age composition of these potentially old edaphic climax forests is uneven. With the exception of those geographic areas in the rainshadow of the Vancouver Ranges or the Olympic Mountains, where summer-dry conditions prevail, fire is not a viable disturbance factor. Although fire is by no means common or frequent, those sites in locations most vulnerable to fire tend to have a major component of Pseudotsuga menziesii in their canopies. Hemlock dwarf mistletoe (Arceuthobium tsugense) is a moderate threat to Tsuga heterophylla (Dorner and Wong 2003, Cadrin and Wolowicz 2005). Within mature and old forests, small gaps result from the death of single trees or small groups of trees due to root-rots, bark beetles or windthrow.