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A Closer Look at Island Mallow (Malva assurgentiflora)
By: Keith Nevison, Director of Horticulture and Operations
Flanking the Pritzlaff Conservation Center on Santa Barbara Botanic Garden’s eastside are strikingly beautiful, tropical-ish plants with a unique connection to our Conservation Team going back decades. Although semi-common in the nursery trade today, island mallow (Malva assurgentiflora), aka malva rosa, royal mallow, or mission mallow, is endemically native only to several California Channel Islands, including the northern islands of San Miguel and Anacapa, and the southern islands of Catalina and San Clemente. Island mallow plants form into two distinct subspecies: assurgentiflora and glabra, with the northern island populations grouped in the former and the southern island plants representing the latter. The subspecies assurgentiflora is a taller, tree-like plant that can reach 12 feet (over 3 meters) tall with maturity, while the southern subspecies glabra is shorter in stature with larger, glossier, and smoother (glabrous) leaves.
Island mallow is currently listed as seriously threatened in California (1B.1) on the California Rare Plant Rank scale due to once widespread grazing by feral and domesticated livestock, which were deliberately introduced to the islands more than a century ago. Thankfully, many of these animals were removed from the islands over the past decade, giving plants the chance to recover and for researchers to step up their restoration efforts to recover the species. In 1992, Steve Junak, then the Garden’s Clifton Smith Herbarium curator, and Sarah Chaney, an experienced Channel Islands National Park ecologist, collected seeds of island mallow from middle Anacapa Island from the last remaining island mallow plants there. Those plants subsequently declined, and Anacapa’s natural populations of island mallow were declared as extirpated or extinct. Restoration work since that time, however, has reestablished appropriate ecotypes of island mallow back on east Anacapa Island, and this work would not have been possible without the collaborative efforts of the National Park Service and the Garden’s joint collection, propagation, and dissemination efforts.
Historically, collections of island mallow that trace genetically from Anacapa Island were planted through many parts of coastal California, from the Bay Area down to Baja California, Mexico, as a garden ornamental and a windbreaking hedge. We find that it performs excellently in our conservation beds surrounding our Island View Section, where it blooms profusely, through many months of the year. Island mallow is a fast-growing plant, best adapted for full sun and low water, and it is listed as a probable host plant for 15 different species of butterflies, moths, and skippers, according to the California Native Plant Society’s Calscape database. Oddly enough, given its rarity and the narrowness of its native home range, island mallow is documented as an escapee in other coastal parts of the world, including Guatemala, western South America, and Oceania. Fun fact: Island mallow is listed as the only Malva that is native to the United States, while seven other nonnative species are listed as being naturalized in Santa Barbara County.
A few garden cultivars exist for island mallow, including some borne from hybrid crosses with Malva pacifica, a species native to the islands off Baja California, and from M. occidentalis, a species exclusively endemic to the Coronado Islands off the coast of the U.S./Mexico border, and to Guadalupe Island, an island located over 160 miles (257 kilometers) approximately west of the provincial boundary between Baja California and Baja California Sur. Some selected cultivars like ‘Blackheart’ and ‘Pastel Stripes’ are said to even have their origin at the Garden and are understood to be plant crosses emanating from a cutting of M. occidentalis that was gifted by the Garden to plantsman Ed Mercurio, which he subsequently planted, allowing for cross-pollination by bees, resulting in deep, rich, and interesting flower colors.
Island mallow makes a wonderful, quick-growing, wind-breaking evergreen hedge, very well-suited for coastal gardens. We are happy to share several handsome specimens in our collection and encourage you to come to the Garden, where you can find it located in the Island View Section, as well as for purchase in our Garden Nursery.
Gardener Tip
If you are interested in growing island mallow in your garden, please note that mallows are very popular with deer and other ungulates, as well as rodents. Having adequate fencing protection is therefore advised.
Citations
Currin, K., Merritt, A., & Spriggs, P. (2023). The California Lavateras and Their Hybrids Pacific Horticulture. https://pacifichorticulture.org/articles/the-california-lavateras/
Hinsley, R. S. (2023). The Lavatera Pages: Californian Lavateras. Malvaceae Info. http://www.malvaceae.info/Genera/Lavatera/californian.html#assurgentiflora
