Lyonothamnus floribundus subsp. asplenifolius

Also known as: Catalina ironwood

Family: Rosaceae

Native to: California (endemic to Channel Islands)

Blooms: late spring to early summer

Habitat: chaparral and oak woodlands of the rocky coastal canyons

Where found at BBG&B: American Bank

This is a beautiful tree from the Channel Islands of California. It is used in the American States as a screen tree, like the blue gum (Eucalyptus globulus). Unlikely the Australian tree though, Lyonothamnus is native there and not invasive. It is also a good choice for coastal conditions.

The trees bear elegant fern-like foliage, with smooth-edged leaves not divided into any leaflets or segments. The flowers are white clusters extending out of the foliage. Unfortunately they don’t appear since the tree is about 10 years old.

Another favourite characteristic is the unique presentation of the bark, which is vividly smooth red-brown but somehow, hidden from long grey strips. In autumn, the gardener can pull off the peeling bark to reveal the beautiful colours beneath.

Like many other Californian plants, Lyonothamnus is fast growing but not very long lived. It is also rather tolerant, which makes it a good choice for contemporary, urban planning schemes where the supply of water is limited.

Lyonothamnus floribundus ssp. aspleniifolius (Santa Cruz Island Ironwood) – This California native evergreen tree is fairly quick growing to a maximum height of 50-60 feet and a width of 15 to 20 feet but is usually seen in cultivation as a slender upright tree with an open canopy no more than 30 feet tall. The main stems and large branches have interesting fibrous shredding gray bark that sheds to reveal deep cinnamon red new bark; the smaller stems, twigs and petioles are this same red color. The 3-5 palmately compound leaves are 4 to 6 inches long by 4 inches wide, with the margins heavily scallop-toothed in triangular lobes. They are unique and quite attractive – said by some to be fern-like but others compare it to the leaves of the marijuana plant (Cannabis sativa). In late spring into summer are produced 4 to 8 inch wide flattened clusters of white flowers that are held out from the foliage at the branch tips. The flowers age first to a chocolate brown and finally to gray – sometimes lingering on the plant for years. Some find the odor of the flowers unpleasant but it is not strong and most rarely notice or comment on this. The leaves and twigs drop to the ground creating an interesting and attractive mulch below the plant. Best along the coast and planted in full to part sun ia well to fairly well drained soil and given infrequent to very little irrigation, but always deeply. In inland gardens it appreciates some shade in the afternoon and more occasional irrigation as well as protection from drying wind. This plant can become chlorotic in heavy soils when given excessive water or where soils do not drain well. Established trees are drought and moderately frost tolerant, taking temperatures down to about 15 degrees F. Older plants can be rejuvenated by cutting down to the basal burl and the hard wood can be used to fashion long lasting garden elements. A great plant for a grove planting or as a specimen where a narrow tree is needed or it can be espaliered with support against a wall, as is done against the library at the Santa Barbara Botanic Garden. Some object to the old flowers that hang on but these can be easily removed with a pole saw. This plant is found growing in the wild on rocky substrates primarily northerly facing slopes of Santa Cruz Island with populations also on two other of the Santa Barbara Channel Islands, San Clemente Island and Santa Rosa Island. The subspecies Lyonothamnus floribundus ssp. floribundus, with leaf margins entire, is found only on Santa Catalina Island. The name for the genus is a combination of the Greek word ‘thamnos’ meaning “shrub” and Lyon to honor William Scrugham Lyon (1851-1916) an early resident of Los Angeles who sent specimens in 1884 from Santa Catalina Island to Asa Gray, who named the plant. Lyon and Rev. Joseph Cook Nevin (who Berberis nevinii is named for) collected together on Catalina Island and Lyon later published an island flora in the Botanical Gazette as Flora of Our Southwestern Archipelago. He was an early Los Angeles area nurseryman, establishing Occidental Nurseries and Elysian Gardens and was appointed the first head of the State Forestry Board. Lyon also explored and collected in Mexico and wrote one of the first California gardening books, Gardening in California published in 1897. Lee Lenz in Native Plants for California Gardens (Rancho Santa Anna Gardens 1956) noted that Lyonothamnus may have been discovered prior to Lyon’s discovery as Professor H.C. Ford of Santa Barbara reported hearing about the Ironwood tree as early as 1875 and Willis Linn Jepson reported in The Silva of California: Memoirs of the University of California, Volume 2 (University Press, 1910) that Katherine Brandegee noted that specimens were sent to Europe by Gustav Eisen with other sources noting that Gustav Eisen discovered it on Santa Catalina Island in 1874 and sent samples to botanists in Europe, but failed to note its taxonomic significance and was therefore not credited with the find. The specific epithet ‘floribundus’ means “abundant flowering”. The subspecies Lyonothamnus floribundus ssp. floribundus from Santa Catalina Island, with leaf margins entire, is very rare and not generally considered as attractive as the subspecies aspleniifolius (meaning “leaves like Asplenium fern”) that comes from San Clemente, Santa Rosa and Santa Cruz islands. This subspecies was first described as a species by the American botanist Edward Lee Greene and later reduced to a subspecies by Townshend Stith Brandegee. It was first brought back from Santa Cruz Island to the mainland by Dr. Francesco Franceschi, who transported a burl stump back in 1894 and plants propagated from suckers off this plant were distributed throughout California by 1905. It was also reported that Franceschi returned with seed and that a large specimen at the Botanic Garden of the University of California, Berkeley was grown from this seed – other reports are that this Berkeley plant was grown from cuttings off of Franceschi’s burl stump and that the collection date may have been as late as 1900. Studies showing extremely low seed viability on the island populations would seem to indicate that the early plants were propagated vegetatively but nearly all nursery crops today are produced from seed. Fossil evidence shows that Lyonothamnus was more widely distributed throughout mainland California up until around 6 million years ago, but now is restricted to only 4 of the Santa Barbara Channel Islands. In 1935 this plant was adopted as the official city tree of Santa Barbara. Authors Greene, Brandegee and Raven in the past have all spelled the subspecies epithet “asplenifolius” with a single “I” in the middle but this spelling has been determined incorrect and in the recent Jepson manual treatment it is now “aspleniifolius”. This plant has long been commonly called Catalina Ironwood in the nursery trade but this is a misnomer as this this name should only apply to the plant native to Catalina Island, Lyonothamnus floribundus ssp. floribundus while the subspecies aspleniifolius should really be called Santa Cruz Island Ironwood. Another common name for it is Fern-leaf Ironwood. The information on this page is based on research conducted in our nursery library and from online sources as well as from observations made of this plant as it grows in our nursery, in the nursery’s garden and in other gardens that we have observed it in. We also will incorporate comments received from others and always appreciate getting feedback of any kind from those who have additional information, particularly if this information is contrary to what we have written or includes additional cultural tips that might aid others in growing Lyonothamnus flor. ssp aspleniifolius.

Plant Database

Lyonothamnus floribundus ssp. aspleniifolius

Lyonothamnus floribundus A. Gray ssp. aspleniifolius (Greene) P.H. Raven

Synonym(s): Lyonothamnus floribundus ssp. asplenifolius, Lyonothamnus floribundus var. aspleniifolius

USDA Native Status: L48 (N)

A slender evergreen tree that can have a single, straight trunk or be branched from the base and shrub-like. It grows quickly from 30-50 ft. and maintains a good form. The exfoliating, red-brown bark; glossy, fern-like, divided leaves; and large, terminal clusters of white flowers with yellow centers are all attractive landscape features.

The genus name, meaning Lyons shrub, honors the discoverer, William Scrugham Lyon (1852-1916), a U.S. horticulturist and forester.

From the Image Gallery

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Plant Characteristics

Duration: Perennial
Habit: Tree
Leaf Retention: Evergreen
Leaf Arrangement: Opposite
Leaf Complexity: Pinnate
Inflorescence: Panicle
Fruit Type: Follicle
Size Class: 36-72 ft.

Bloom Information

Bloom Color: White
Bloom Time: May , Jun


Native Distribution: Channel Islands, CA
Native Habitat: Dry slopes & bluffs below 500 ft.

Growing Conditions

Light Requirement: Sun
Soil Description: Well-drained soils with at least 15 in. precip./yr.
Conditions Comments: Not Available


Description: Propagation by seed is fast.
Seed Collection: Not Available
Seed Treatment: Seeds germinate without pretreatment.
Commercially Avail: yes

From the National Organizations Directory

According to the species list provided by Affiliate Organizations, this plant is on display at the following locations:
Santa Barbara Botanic Garden – Santa Barbara, CA


Bibref 995 – Native Landscaping from El Paso to L.A. (2000) Wasowski, S. and A. Wasowski
Search More Titles in Bibliography

Additional resources

USDA: Find Lyonothamnus floribundus ssp. aspleniifolius in USDA Plants
FNA: Find Lyonothamnus floribundus ssp. aspleniifolius in the Flora of North America (if available)
Google: Search Google for Lyonothamnus floribundus ssp. aspleniifolius


Record Modified: 2011-08-26
Research By: TWC Staff

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Horticulture Blog

Santa Cruz Island Ironwood (Lyonothamnus floribundus ssp. aspleniifolius)

Lyonothamnus floribundus ssp. aspleniifolius is a mouthful to say but there is nothing edible about this tree. Lyonothamnus is endemic to the Channel Islands of California, where it grows in the chaparral and oak woodlands of the rocky coastal canyons. Lyonothamnus is a monotypic genus of trees containing the single living species Lyonothamnus floribundus, which contains the two subspecies: L. f. ssp. aspleniifolius and L. f. ssp. floribundus. The subspecies ssp. aspleniifolius is the more common species and grows wild on the following three Channel Islands: Santa Cruz Island, San Clemente Island and Santa Rosa Island; whereas, ssp. floribundus is limited to Catalina Island of the Channel Islands. Santa Cruz Island Ironwood is a somewhat shaggy tree that can grow to 35’ in ideal conditions.

A former professor from my junior college days once said, “I wouldn’t plant that scruffy dog within 100’ of my house”. Ironwood, as it is commonly called, does drop a great deal of debris from its branches in the form of dead flower heads and copious amounts of dead leaves. So keep this in mind when choosing a location to plant an Ironwood, though its beauty far outshines its untidiness.

Ironwood is known to be quite drought tolerant after establishment, making it a good choice on seashore properties. Its ability to tolerate salty winds, poor soils, extended dry periods, be mostly pest free, and be slow growing are only the beginning of its attributes. By far, the most impressive feature of this tree is its foliage of lobed, compound dark green glossy leaves. From April through May it has creamy, white umbels (flowers) that provide bees with a good source of native pollen. Lastly is its stunning fibrous red-brown to grayish bark that sheds to reveal deep cinnamon red new bark as the tree matures.

This small tree needs some room to grow. I would suggest it has at least a 10’ by 10’ area to establish itself. I have seen them planted as a windbreak and they look fine in a row. Ironwood is mostly propagated by cutting and can also be grown from seed. In the beginning, protection from deer, rabbits, and gophers may be necessary; I recommend a temporary 4’ high garden fence around the tree as well as planting inside a gopher basket. (All these items can be purchased at most hardware stores.)

It is not really necessary to use a soil amendment but probably wouldn’t hurt to do so. Adequate water in the beginning is necessary, so build a basin around the trunk large enough to handle a 5-gallon bucket of water and water weekly for the first month to ensure quick establishment. Follow up with bi-weekly watering through the second and third months. After that, monthly watering should be fine. This is just a general watering guideline so you will need to use your best judgment. By the way, you can use this water guideline on any plant. Now that I have told you all about Ironwood, I’m guessing you might want to know where to get one. Luckily Lyonothamnus floribundus ssp. aspleniifolius (Santa Cruz Island Ironwood) is readily available in the nursery trade and you should not have any problems purchasing this very rare and unusual species.

Until next month, Happy Gardening.
John Nowak and Suzette Girouard, Plant Sale co-Chairpersons.

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