Hibiscus are a stereotypical tropical flower (Hibiscus rosa-sinensis which is a tender tropical that is killed by freezing temperatures) but there are several species and hybrids that do well in the Midwest. For a show-stopping plant when in bloom, the old reliable ‘Lord Baltimore’ hibiscus is hard to beat. This moderately tall plant with bold crimson flowers is an improved sterile hybrid that was introduced in 1955. It was hybridized by Robert Darby from several Hibiscus species native to wetlands of the eastern U.S., including H. coccineus, H. laevis, H. moscheutos, and H. palustris. It is still one of the best pure red cultivars and is hardy in zones 4-9.
This vigorous, somewhat shrubby herbaceous perennial grows 4-5 feet tall and 2-3 feet wide (or even bigger in some locations) and dies back to the ground in winter. The new shoots emerge very late in the spring (mid-June many times), but then grow quickly. The reddish brown stems are sturdy and erect and are almost woody at the base. Plants grown in the proper environment usually do not need staking. The
glossy, medium green leaves are deeply lobed (an exaggerated maple shape), creating a relatively coarse texture, with burgundy petioles.
Flowers are produced profusely from mid-summer to early fall (about July through September). Each satiny flower is up to 10″ across, with five ruffled petals that overlap slightly and a prominent central staminal column. Each flower only lasts a day, but one or more flowers usually open each day. The spent flowers will eventually fall to the ground but deadheading regularly improves the appearance of the plant.
‘Lord Baltimore’ makes a great specimen on its own or in masses. It can be used at the back of a perennial border or as an airy screen or hedge. It’s a great accent plant when in bloom, but many people are not fond of the foliage. It combines well with other mid-to late-late summer bloomers, such as purple coneflower (Echinacea purpurea), blackeyed Susans (Rudbeckia spp.), sunflowers and ornamental grasses. Surround it with cannas and elephant ears for a tropical feel to your landscape.
This hibiscus cultivar does best in moist soils rich in organic matter but is easily grown in most average to wet soils and therefore is quite useful in low spots and along streams or ponds. It also does well in clay soils. Regular deep watering is recommended in soils that are not naturally consistently moist. It does best in full sun but will grow in light shade, although flowering will not be as good. Stems are susceptible to breaking at ground level in severe winds, so consider planting in a protected site if you are in a windy location. Fertilize when growth begins and again midseason. Cut the stems back to a few inches in late autumn (leaving enough to mark the location of the slow-emerging plants in spring). A winter mulch may help survival in colder zones.
Hardy hibiscus generally do not have any serious pest problems, although Japanese beetles can cause significant defoliation and deer like this plant in some places (but don’t always favor it).
This cultivar and other hybrids can only be propagated vegetatively. Take stems cuttings in early fall. Cultivars of H. moscheutos or other species from which the cultivars were derived can be grown from seed.
In addition to ‘Lord Baltimore’ there are many other spectacular hybrid cultivars of Hibiscus that are hardy to zones 4 or 5, as well as named selections of H. moscheutos. These are just a few of the many available:
- ‘Blue River II’ – large pure white flowers and blue-green foliage.
- ‘Disco Belle’ series – a semi-dwarf strain of H. moscheutos (2-3 feet tall) with flowers in pale pink, dark pink, rose, red or white all with a red eye.
- ‘Lady Baltimore’ – flowers are pink with a red eye
- ‘Luna’ series – another low-growing H. moscheutos strain includes white, blush, pink, rose, red, and pink swirl. Good for large containers.
- ‘Moy Grande’ – exceptionally large (to 12″) rose-pink flowers in flushes of bloom through the summer. Deadheading promotes reblooming.
- ‘Turn of the Century’ – pinwheel striped flowers in dark red and light pink.
– Susan Mahr, University of Wisconsin – Madison