Pycnanthemum tenuifolium produces an impressive display of white flower clusters. It is multi-branched and dense, yet the needle-like foliage gives it an airy and even delicate appearance. As the common name indicates, narrowleaf mountainmint has distinctively slender leaves, that are up to 3" long and a mere 1/4" wide. It is not as tall as most Pycnanthemums and generally does not exceed a height of 30".

Narrowleaf mountainmint spreads enthusiastically via rhizomatous roots, and can create an excellent groundcover and weed barrier for full to part-sun. It is easy to grow and not particular about soil type and will even adapt to thin, rocky ones. It produces a tap root which helps it withstand prolonged dry spells. Like most mountainmints, it can behave a bit like a thug in the garden and it is best to give it its own space. It can also be used as a border planting, to take advantage of its airy appearance, in front of taller and robust flowering perennials and grasses. [source: izelplants.com]