The ultimate cottage garden perennial hollyhock rosea 39pleniflora39 produces fully double pink pom45pom blooms all the way up its impressive 18m 4063941 tall stems the tall slender habit of hollyhocks makes them perfect for planting in close groups for maximum effect thriving in sunny borders grow hollyhock 39pleniflora39 towards the back of the border to add height and drama to summer planting schemes height 180cm 40713441 spread 60cm 402434