The effects of canopy gaps on forest understory communities are well documented. However, there has been almost no documentation of the effects of gaps on the canopies themselves. Recent research has shown that portions of crowns adjacent to gaps undergo rapid growth, implying an increase in available carbohydrate (due to increased sunlight). It is reasonable to hypothesize that this would also lead to increases in flowering, fruiting, and epiphytic growth in these same crown portions. Limited data from a temperate forest presented here suggest that this is true. If so, gap-edge tree crowns could be hot spots of resource availability for folivores, floral visitors, frugivores, epiphytes, and associates of these species. As yet we have no documentation of these hot spots or how deeply their effects penetrate into the adjacent parts of the canopy. Because of limited access, canopy biology has concentrated on the vertical dimension, but studies in the horizontal dimension are equally important. Using examples from 'gaps' (glades) in an acacia bushland in East Africa and terrestrial temperate forest edges, I show how similar landscape mosaics have highly variable effects on the community, depending on the traits considered. I then consider parallels with forest canopy gaps, and possibilities for future research.