Zone: 4 to 8
Soil: sand to loam
Light: Full sun to part sun
Bloom colour: White
Bloom period: July to August
Height: 2 to 3 feet
Moisture: Dry to medium
Attracts: A variety of bees and wasps.
Notes: If I were forced to plant just one species to attract bees and butterflies, it would be a mountain mint. These plants attract a huge diversity of bees and beneficial wasps and they are a dream plant for entomologists. They have a long blooming period and they are easy to grow. Pycnanthemum virginianum, the most common species, grows well in a variety of conditions and is quite drought tolerant. P. tenuifolium is more drought tolerant while P. pilosum is more tolerant of clay soils. All three of these plants, which look very similar to each other, are native to Ontario and a large part of the North East. All of them naturally occur in prairies and savannahs.
Another species worth mentioning is Pycnanthemum muticum, which has various common names. In addition to the flowers, it has large silvery bracts which add a lot of ornamental value for gardeners. It requires good drainage, but it is not drought tolerant. It will grow well in part-sun. It is native to the Eastern half of the USA.
These plants to spread out a bit, but they are not that large. so it is worth planting a few together. They are easy to keep in check by pulling or by using root barriers.
In addition to the three species already mentioned, Pycnanthemum incanum is also native to Ontario and has a provincially endangered status.