Cover, undergrowth, shrubbery; all terms for a mass of woody growth that provides shelter to biodiversity. Flowers, foliage and fruit through the seasons add to the interest of a group of species that may through their growth habit inadvertently smother out all other vegetation in their path. Two North American species that spread themselves by way of suckering growth are Rosa californica (Western USA and Northern Mexico), and Viburnum lentago, (NE USA). From the attached image the slim, vigorous root system of the Viburnum with sucker growth well advanced and protruding upwards can be seen. Both the Viburnum and the Rose rapidly, once established, are able to colonise a sizeable area of ground in a season. With maturity and consecutive years of growth comes a ground mulch of organic matter as the foliage grows, drops and dies. The mulch layer binds and gradually soil improvement results.