Growing Hardy Hibiscus in Zone 4
Hibiscus plants for cold climates are difficult to come by, as most of the hardy hibiscus plants only tolerate winter chill to zone 5. That being said, Hibiscus moscheutos, also called Rose Mallow or Swamp Mallow, is a zone 4 hardy hibiscus that was developed in the 1950s by the three Fleming brothers. These hibiscus plants for zone 4 have lots of big, bright flowers that bloom in late summer. The flowers themselves are somewhat short-lived, but there are so many of them that the plant remains colorful for a long time. The plants are difficult to transplant, so pick your location with care. They like full sun but can handle a little bit of shade. They will grow to about 4 feet (1 m.) high and 3 feet (1 m.) wide, so leave them plenty of space. They do well in most types of soil, but they grow best in moist, rich soil. Amend with some organic material if your soil is very clay heavy. The zone 4 hardy hibiscus is an herbaceous perennial, which means it dies back to the ground each winter and regrows from its roots in the spring. Allow your plant to die back with the autumn frost, then trim it down to the ground. Mulch heavily over the stump, and pile snow on top of the spot when it comes. Mark the location of your hibiscus – the plants can be slow to start in the spring. If your plant gets hit by a spring frost, prune back any damaged wood to allow for new growth.
