Marsh Mallow Seeds althoea officinalis – is most often encountered in damp areas near coasts such as salt marshs, grassy ditches and banks. In wildflower gardens Marsh Mallows are ideal for including in a sunny flower border where the flowers will attract butterflies. Marsh Mallow typically grows to about 2 foot high and is late flowering, with pale pink flowers that appear in August and September. Marsh Mallow looks best growing with other late flowering wetland plants such as Purple loosestrife and Hemp agrimony.