Leitneria floridana Chapm.

Leitneria probably receives more attention from taxonomists than from horticulturists. A botanical oddity, it can nevertheless be recommended for planting in very moist sites or even in water. In this account of its horticultural usage we cover all taxa, as it is unclear to which any cultivated plants belong.

In habitat, Corkwood thrives in freshwater or tidal swamps, marshes, and floodplains. These habitats are often damp and poorly drained, making them ideal for Corkwood’s growth (Chafin 2020). The wood is extremely light, with a specific gravity lower than the cork of its common name (0.21 vs 0.24), though not as light as balsawood, from which Thor Heyerdahl’s raft Kon-Tiki was made (Bean 1981a). It has traditionally been used for fishnet floats or bottle stoppers (Bogle 1993).

It is cold hardy well north of its range, being successfully cultivated in Chicago, Rochester and Boston (Bogle 1993). Dirr dismisses its ornamental value but admits it can be ‘rather interesting planted in moist soil along a brook or moist depression where it forms a large thicket of grove-like proportions’ (Dirr 2009). At the Arnold Arboretum it has prospered in a location dubbed Leitneria Bowl (or ‘swamp’), where water accumulates and persists through most of the year (Enzenbacher 2021). Here the original collections, from both western and eastern populations, have grown together so completely that they are treated as one accession. With their suckering and layering habit this is inevitable and accessions should be kept widely spaced if they are to remain recognsisable (M.Dosmann pers. comm. 2025)

Koller recommends the shrub for wet, shaded locations, noting that it tolerates both shade and wet soils, a characteristic rarely found in one shrub. It can grow in both fresh and brackish water, which might make it useful in poorly drained urban planting islands or other plantings subjected to extremes of soil moisture and salt spray (Koller 1997). A study by Sharma and Graves (2004) suggested that the tolerance of L. floridana to shade, low and high soil moisture, and nutrient-poor soil in native habitats indicates that it could be used in a wide range of managed landscapes, though Michael Dosmann (pers. comm. 2025) advises that at the Arnold Arboretum it only thrives in wet places, and thinks its use is really only limited to ‘mesic spillways and very rainy rain gardens.’

The flowers of Corkwood are small and borne in catkins before the leaves emerge in early spring. Male catkins are yellowish-brown and longer than the dark red female catkins. Fruits are leathery, one-seeded, and turn from yellow to brown as they mature. These fruits are likely dispersed by animals; sexual reproduction is limited due to habitat fragmentation that separates male and female colonies (Chafin 2020).

The plant reproduces sexually but vegetative reproduction is predominant, leading to the formation of large clones from adventitious buds on shallow roots (Bogle 1993). Small, pencil-thin divisions lifted soon after spring thaw develop a strong root system in two to three months and by the second spring send up new shoots. It is also easily propagated from layers: a layer planted in autumn produces eight to twelve new suckers by the following autumn (Koller 1997). Suckers extracted in the wild have been used to bring plants into cultivation (Enzenbacher 2021).

It does not suffer significant damage from pests. Minor damage was reported at Missouri Botanical Gardens from Atteva punctella, the Ailanthus webworm, whose caterpillars make small holes in the young leaves, but nothing that required control (Koller 1997).

Despite its resilience, Leitneria floridana faces significant threats. Habitat loss due to ditching, draining and development of wetlands has severely impacted its distribution. Climate change poses additional risks through altered rainfall patterns and saltwater intrusion into freshwater habitats (Chafin 2020). It is Near Threatened according to IUCN (Carrero & NatureServe 2022) and at a state level it is Vulnerable in Florida and Imperiled in Georgia (NatureServe 2018).

Leitneria was introduced into cultivation in 1894 at the Arnold Arboretum from material received from B.F. Bush, who had found the plant in Missouri two years before (Trelease 1895). (As this corresponds to the native range of L. pilosa subsp. ozarkana, it would appear that it was this taxon that was cultivated first.) Bean saw it in 1910 at the Arnold, in the New York Botanical Garden and Highlands Park, Rochester, New York, where he was impressed by what he called ‘this remarkably interesting tree.’ He introduced it to Kew that year and already by 1914 included it in a list of plants recommended for wet places. He did express doubts, however, regarding ‘its capability of permanently supporting [Britain’s] duller climate’ (Bean 1914). It has not proved popular in horticulture in Britain and Europe, remaining a botanical oddity found mainly in botanical gardens and specialist private gardens.

The epithet ‘floridana’ means ‘from Florida,’ in reference to the state where it was found.