Old-growth stands have structural complexity as defined by multiple canopy layers:
overstory layer with large diameter trees
midstory layer with shade tolerant trees such as hemlock, redcedar or silver fir
understory layer with shrubs, herbaceous plants (having little or no woody tissue) and some tree regeneration
In our restoration work we want to encourage development of the native plant communities present in the understory and midstory of old-growth forests. Many stands especially need to develop a midstory tree layer. In addition, we don't want to introduce non-native plants like tulips - even if Mr. Hubbart thinks they are pretty. We do want to encourage development of plant communities associated with old-growth forests.