Hibiscus lasiocarpos / Hibiscus moscheutos / Hibiscus laevis
By Jim Lakin, MD, Master Gardener
As Juliet observed of her beloved Romeo, “What’s in a name? That which we call a rose by any other name would smell as sweet.” We may then ask, “Would that which we call a rose be less beautiful if it is not?” To this I would unhesitatingly say, “Yes in the case of the rose mallow”. H. lasiocarpos and H. moscheutos are nearly identical members of the mallow family (Malvaceae). They are native to most of the Lower Midwest and northward to areas around Lakes Michigan and Erie. Their closely related cousin, the somewhat more cold-tolerant Halberd-leaved rose mallow (H. laevis) is native to Southeast Minnesota and up the Missouri River Valley. The rose mallows are hardy through zones 4-9. These perennials are closely related to the much-prized tropical hibiscus.
As you might expect, this gorgeous plant has been hybridized into a large number of attractive cultivars available at your local nursery. The value of these cultivars to our pollinators remains to be determined. There is no question, however that the three native species are key players in the ecological web of the Northern Midwest. They are very nectar and pollen rich, being great additions to a pollinator garden.
The rose mallows are essentially a wetlands plant found around lakes and rivers. They may even be seen growing in standing water. They do well though in moist, well-drained soil in full sun. If they are in a bed, remember to water them during dry, mid-summer weather. They eventually grow to about five feet so you should keep that in mind if inserting them into a border garden. They do well as a backdrop to sun loving ground covers. Rose mallow is slow to emerge from dormancy but once in gear it is a rapid grower, putting on as much as an inch per day. The blooms are quite showy, appearing from July to September so you would do well to mix them with earlier blooming perennials such as Jacob’s Ladder or creeping phlox. The flowers are from three to five inches across with a red center “eye” from which the stamen protrudes. Flower petals may vary from white to shades of pink.
Once established, application of a slow-release fertilizer in the spring can enhance growth. While you are at it, pruning back the old growth to about six inches will help to make way for the new foliage. Deadheading usually is not necessary. Rose mallow winters over pretty well although putting a couple of inches of mulch over the plants in the fall will reduce the chance of winter kill. So, if you have a riverbank, marsh or rain garden to plant, you would do well to incorporate the lovely rose mallow.