The Mixed Shrub complex is typically a lush mixture of shrub and herb species. Common shrubs associated with this community are thimbleberry, red raspberry, falsebox, black twinberry, red elderberry, devil’s club, false azalea, red-osier dogwood, Douglas maple, willow and Sitka alder, while common herbs include fireweed, lady fern, bracken, and grasses. Not all of these species will be present on every site. The Mixed Shrub, Fern, and Fireweed complexes often include the same species, but as long as shrubs are dominant, the community is classified as Mixed Shrub. In southern interior British Columbia, the Mixed Shrub complex is common on moist to wet sites in the ICH biogeoclimatic zone, including those that are transitional to the ESSF zone. It generally occurs on sites that are highly productive for conifer growth.

Increased light availability following harvesting stimulates growth of many of the species associated with the Mixed Shrub complex (e.g. thimbleberry, red raspberry, red elderberry, Sitka alder, fireweed, and bracken) but has variable or minimal effect on other species (e.g., false azalea, Douglas maple, and lady fern). Development of the Mixed Shrub complex is encouraged by light to moderate burns and low-impact soil disturbance during logging or mechanical site preparation treatments that stimulate re-growth and provide suitable seedbeds for germination of new or banked seed. In contrast, intense burns and high-impact mechanical site preparation hinder development of the complex by destroying roots and rhizomes in the upper soil horizons.

Invasion of the Mixed Shrub complex is usually rapid following disturbance; it develops on highly productive sites and most of the plant species are present before logging. The community can reach 100% cover and a height of 1-1.5 m within 1-2 years of logging.

The Mixed Shrub complex can compete strongly with young conifer seedlings, mainly by reducing available light and causing physical damage from vegetation- and snow-press. Competition is particularly serious on subhygric sites where vegetation develops abundantly. Competition for moisture and nutrients is probably of minor importance because the complex occurs mainly on moist to wet, rich sites.

Typical development of the Mixed Shrub complex 3 years after mechanical site preparation. Thimbleberry and willow are the dominant species.