Bush Rose Shrub Rose Difference . As far as horticulture (the art and practice of garden cultivation) is concerned, there is no exact definition of when a plant is a shrub or a bush. Rose bush is small, rose shrub is medium, rose tree is large.lol. Rose Absolutely Fabulous Floribunda Rose Bush and Shrub Roses from www.gardeningexpress.co.uk Mix in a handful of bone meal to support root development. Shop all miniature roses shrub roses True wild roses have only 5 petals and occur naturally, being native to north america, europe and asia.