Mac H. Alford* and Irina V. Belyaeva**
University of Southern Mississippi (USMS)*Royal Botanic Gardens, Kew**
Trees or shrubs, with or without thorns or spines. Leaves alternate or rarely opposite or subopposite (Abatia Ruiz & Pav.), simple, pinnately or palmately veined, sometimes acrodromous perfect (3-veined from base to apex: Lunania Hook., Neosprucea Sleumer); margins entire to crenate, serrate, dentate, or spinose; leaf teeth, if present, with small conical, deciduous appendages or with persistent, papillate to globose to torus-(doughnut-)shaped glands; infrequently with stellate pubescence (some Abatia, Banara Aubl., Macrohasseltia L.O.Williams, Pineda Ruiz & Pav., Ryania Vahl); lamina sometimes with pellucid-punctations or -lines (tribe Samydeae); exstipulate or stipulate, stipules sometimes large and falcate (e.g., Prockia P.Browne ex L., Salix L.) or even leaf-like (Azara Ruiz & Pav.). Sexuality various, usually hermaphroditic, polygamous, or dioecious. Inflorescences axillary or terminal, catkins, spikes, racemes, panicles, cymes, corymbs, umbelliform cymes, fascicles, or glomerules, or reduced to single flowers. Flowers actinomorphic or irregular (tribe Saliceae), often minute. Hypanthium present or absent. Sepals absent (tribe Saliceae), otherwise 3-15(-22), aestivation imbricate or valvate. Petals absent or 3-8(-12), aestivation imbricate or valvate. Disk sometimes present, in some groups appearing like thick staminodes and in other groups like globose nectaries, inside, alternating with, or outside the stamens. Stamens (1-)2-numerous, sometimes in epipetalous bundles; anthers globose to linear-elongate; anther dehiscence introrse (tribe Samydeae), extrorse, or latrorse (Lunania), dehiscence usually longitudinal (± poricidal in Neosprucea). Gynoecium of 1 pistil, ovary superior or half-inferior (Homalium Jacq.), generally unilocular (occasionally with septa in Dovyalis E.Mey. ex Arn., Flacourtia L'Her., Hasseltia Blume, Prockia), placentation parietal or pseudo-axile, styles 1-8, stigma capitate to lacerate to obscure. Fruit a fleshy or dry berry, capsule, samara (Neopringlea S.Watson), or drupe (Flacourtia). Seeds 1-numerous, arillate or exarillate, sometimes covered in cottony hairs (Bartholomaea Standl. & Steyerm., Casearia Jacq. sect. Gossypiospermum Urb., Macrohasseltia) or with a coma (Populus L., Salix).
Notes on delimitation
- Salicaceae were traditionally a mostly temperate family consisting of two genera, Populus (poplars, cottonwoods, aspens) and Salix (willows).
- Recent phylogenetic analyses using DNA sequence data, however, indicate that Salicaceae sensu stricto are nested within the non-cyanogenic taxa of the former Flacourtiaceae. These taxa have now been united into one family, the Salicaceae (Eurosids I: Malpighiales), which is closely related to Lacistemataceae, Passifloraceae, Violaceae, Achariaceae, and allied families.
- Some botanists (the author included) prefer to segregate one tribe of Salicaceae sensu lato as a separate family (Samydaceae), leaving the rest as a Salicaceae sensu medio, but this approach has not been widely accepted.
- The former Flacourtiaceae have been a notorious family, principally because Flacourtiaceae are diverse morphologically and because the family has served as a garbage can for taxa of uncertain affinity. Several key studies in the past 30 years have mostly eliminated the latter problem, but unfortunately, the former "problem" continues to persist in the current Salicaceae sensu lato. Thus, for the novice, the description and advice of Al Gentry is pertinent: "One of the two most notoriously heterogeneous neotropical families. A good dictum for the beginner is: 'If you don't have any idea what family it is, try Flacourtiaceae [now mostly Salicaceae sensu lato] or Euphorbiaceae'" (Gentry, 1993).
Distribution in the Neotropics
- Abatia Ruiz & Pav. (including Aphaerema Miers): montane Central and South America, SE Brazil.
- Azara Ruiz & Pav.: Chile, Argentina, Bolivia, and SE Brazil, mostly subtropical and temperate.
- Banara Aubl.: Antilles, Mexico, Central and South America, especially diverse in the Antilles.
- Bartholomaea Standl. & Styerm.: Mexico, Guatemala, and Belize.
- Casearia Jacq.: Antilles, Mexico, Central and South America.
- Dovyalis E.Mey.: cultivated for fruit, throughout.
- Euceraea Mart.: South America.
- Flacourtia L.'Her.: cultivated for fruit, throughout.
- Hasseltia Blume: Central and South America.
- Hasseltiopsis Sleumer: Central America.
- Hecatostemon S.F.Blake: northern South America.
- Homalium Jacq.: Antilles, Mexico, Central and South America.
- Laetia Loefl.: Antilles, Central and South America.
- Lunania Hook.: Antilles, Central and South America, most diverse in the Antilles.
- Macrohasseltia L.O.Williams: Central America.
- Macrothumia M.H.Alford: Brazil.
- Neopringlea S.Watson: Mexico and Guatemala.
- Neoptychocarpus Buchheim: South America.
- Neosprucea Sleumer: Panama and South America.
- Olmediella Baill.: Mexico and Central America.
- Pineda Ruiz & Pav.: montane Ecuador, Peru, and Bolivia.
- Pleuranthodendron L.O.Williams: Central and South America.
- Populus L.: Mexico, but infrequently cultivated elsewhere.
- Prockia P.Beowne ex L.: Antilles, Mexico, Central and South America.
- Ryania Vahl: Central and South America.
- Salix L.: Mexico, Central and South America.
- Samyda Jacq.: Antilles, Mexico, and Central America.
- Tetrathylacium Poepp. & Endl.: Central and South America.
- Xylosma G.Forst. (including Priamosia Urb.): Antilles, Mexico, Central and South America.
- Zuelania A.Rich.: Antilles, Central and northern South America.
Distinguishing characters (always present)
- Trees or shrubs.
- Leaves simple.
Other important characters
- Placentation usually parietal (axile or pseudo-axile in few genera).
- Leaves pellucid-punctate or -lineate in tribe Samydeae.
- Leaves usually alternate (except opposite in Abatia) and commonly toothed.
Key differences from similar families
- Salicaceae can be confused with a large number of other families. They are commonly mistaken for Euphorbiaceae, Violaceae, or Malvales.
- Unlike Euphorbiaceae, many common Salicaceae have torus- (or doughnut-) shaped glands at the leaf teeth and never produce a milky latex.
- Salicaceae can usually be distinguished from Malvales if flower or fruit (and placentation) is available, but even then, some Salicaceae have highly intruded to pseudo-axile placentation; few Salicaceae also have stellate pubescence and petiolar pulvini, although not both in the same species (as currently known).
- Salicaceae tend to have more stamens (>5) and less elongate fruit than Violaceae.
- Infrequently, species of Salicaceae with pellucid -punctuations or -lines may be confused with Rutaceae, but the leaves of Rutaceae are usually compound and the flowers usually have an intrastaminal, annular nectary disk.
- The opposite-leaved Abatia is easily confused with Buddleja L. (Buddlejaceae) or Viburnum L.(Adoxaceae) in the vegetative state; again, leaf teeth are helpful. In flower, they can be distinguished because Abatia lacks petals and generally has more than 5 stamens, all free.
- Tribe Saliceae (Populus and Salix) may be confused with Lacistemataceae, a closely related family with catkin (or catkin -like) inflorescences. Lacistemataceae usually have bisexual flowers, some perianth, arillate seeds, and a single stamen with an expanded connective. Populus and Salix rarely have one stamen, are usually dioecious, apparently lack perianth (minute in Populus and only clear early in development), and generally have two or more stamens.
Number of genera
- Abatia (including Aphaerema Miers) - 10 spp.
- Azara - 10 spp.
- Banara - ca. 35 spp.
- Bartholomaea - 2 spp.
- Casearia (sometimes placed in Samydaceae) - ca. 180 spp. worldwide, ca. 80 in the Neotropics.
- Dovyalis - ca. 15 spp. worldwide, 1 sp. infrequently cultivated in the Neotropics.
- Euceraea (sometimes placed in Samydaceae) - 3 spp.
- Flacourtia - ca. 15 spp. worldwide, 1(+?) sp. infrequently cultivated in the Neotropics.
- Hasseltia - 4 spp.
- Hasseltiopsis - 1 sp.
- Hecatostemon (sometimes placed in Samydaceae) - 1 sp.
- Homalium - ca. 200 worldwide, 3 in the Neotropics.
- Laetia - 10 spp.
- Lunania (sometimes placed in Samydaceae) - 14 spp.
- Macrohasseltia - 1 sp.
- Macrothumia - 1 sp.
- Neopringlea - 3 spp.
- Neoptychocarpus (sometimes placed in Samydaceae) - 2 spp.
- Neosprucea - 9 spp.
- Olmediella - 1 sp.
- Pineda - 2 spp.
- Pleuranthodendron - 1 sp.
- Populus - ca. 32 spp. worldwide, ca. 4 spp. in the Neotropics (2 native, 2 introduced and naturalized).
- Prockia - ca. 6 spp.
- Ryania (sometimes placed in Samydaceae) - ca. 8 spp.
- Salix - ca. 450 spp. worldwide, 17 in the Neotropics (11 native, 5 introduced and 1 naturalized).
- Samyda (sometimes placed in Samydaceae) - 9 spp.
- Tetrathylacium (sometimes placed in Samydaceae) - 2 spp.
- Xylosma (including Priamosia Urb.) - ca. 95 spp. worldwide, ca. 50 in the Neotropics.
- Zuelania (sometimes placed in Samydaceae) - 1 sp.
Useful tips for generic identification
Key to genera of Neotropical Salicaceae
See also Alford (2003) for an even more superficial key (Populus and Salix were not included; Macrothumia is treated as Banara; and a new species of Pineda keys incorrectly).
1. Leaves opposite ... Abatia1. Leaves alternate 2
2. Leaves 3-7-veined from the base 3 2. Leaves pinnately veined 18
3. Inflorescences of catkins, spikes, compound spikes, spike-like racemes, or panicles of spikes; leaves sometimes pellucid-punctate or -lineate 43. Flowers solitary or inflorescences of fascicles, lax racemes, panicles, cymes, or compound umbelliform cymes; leaves never pellucid-punctate or -lineate 7
7. Anthers linear-elongate, anther dehiscence ± poricidal; leaves often 3-veined from base to near apex with perpendicular tertiary veins... Neosprucea7. Anthers globose, anther dehiscence longitudinal; leaves 3-veined from base to no more than 2/3 leaf length 8
11. Fruit a samara; stamens in bundles of 3 alternating with disk glands; petals lacking in female flowers ... Neopringlea11b. Fruit a berry; stamens numerous (>20), not in bundles; petals present in female flowers ... Hasseltiopsis
12. Fruit a drupe; disk glands in a row outside the stamens; leaves (in Neotropical cultivated sp.) glabrous or glabrescent ... Flacourtia12. Fruit a pubescent berry; disk glands alternating with stamens; leaves (in Neotropical cultivated sp.) with pubescence visible with the naked eye, especially on the veins... Dovyalis
13. Glands at leaf teeth (at maturity) abaxial and doughnut (= torus) shaped; disk glands< /A> lacking 1413. Glands at leaf teeth, if present, marginal and papillate; disk glands present 15
14. Inflorescence a raceme; placentation often pseudo-axile; petals sometimes lacking; stipules sometimes foliaceous; sexuality various ... Prockia 14. Inflorescence a panicle, raceme, or fascicle; placentation parietal to highly intruded parietal; petals present; stipules small, caducous; bisexual... Banara
15. Glands near apex of petiole, if present, usually not paired and not opposite each other; outer row of filamentous staminodes present .... Pineda15. Glands at base of lamina or near apex of petiole paired and opposite each other; filamentous staminodes lacking 16
16. Placentation axile or pseudo-axile; perianth persistent in fruit; a pair of elliptic leaf glands embedded in the base of the lamina... Hasseltia 16. Placentation parietal; perianth deciduous in fruit; a pair of cicular leaf glands projecting from the lamina-petiole junction or apex of the petiole 17
19. Dioecious; sepals 7-15(-22); stamens numerous; leaves not pellucid-punctate or -lineate .... Olmediella19. Bisexual; sepals 5-6; stamens 6-10; leaves sometimes pellucid-punctate or -lineate .... Casearia sect. Casearia informal group 'Ilicifoliae' 20
20. Flowers lacking any obvious perianth; inflorescences of catkins; fruits capsules; seeds with cottony pubescence 2120. Flowers with at least sepals present; inflorescences various, not catkins; fruits generally berries or tardily deshicent capsules; seeds usually lacking cottony pubescence (except Casearia sect. Gossypiospermum) 22
23. Inflorescences of spikes, compound spikes, or panicles of spikes 2423. Flowers solitary or inflorescences of fascicles, racemes, cymes, or panicles 26
25. Stamens 10-20; foliaceous stipules sometimes present; leaves <10 cm long; sepals generally yellow ... Azara25. Stamens 4; stipules not foliaceous; leaves >8 cm long; sepals generally white or red ... Tetrathylacium
26. Petals present 2726. Petals absent 28
27. Sepals and petals generally 3; disk glands lacking; outer filamentous staminodes lacking .... Banara27. Sepals and petals (4-) 5 (-6); disk glands present; outer filamentous staminodes present .... Pineda
28. Thorns on trunks or branches present 2928. Thorns on trunks or branches absent 33
29. Flowers usually unisexual; sepals free; leaves not pellucid-punctate or -lineate 3029. Flowers bisexual; sepals united at the base (sometimes up to 1/3 or more) with stamens forming a hypanthium; leaves usually pellucid-punctate and/or -lineate 32
31. Fruit a glabrous drupe; disk glands in a ring outside the stamens; style branches 4-6 (each with bilobed stigmas) .... Flacourtia31. Fruit a pubescent berry; disk glands alternating with the stamens; style branches 5(-7) .... Dovyalis
32. Disk lobes and stamen filaments free or only united near the base; flowers few to numerous per inflorescence.... Casearia sect. Casearia -OR- Casearia sect. Guidonia32. Disk lobes and stamen filaments united almost completely or disk lobes apparently absent; flowers generally 1-3 per inflorescence.... Samyda
33. Glands present at the base of the leaves or on petioles 34 33. Glands absent at the base of the leaves or on petioles 35
35. Bracts united into a cup below the flowers and fruits 36 35. Bracts free 37
36. Stamens 30-50; seeds arillate; fruits frequently with rust-colored pubescence .... Laetia sect. Scypholaetia36. Stamens 8-10; seeds exarillate, covered in cottony pubescence; fruits glabrous.... Casearia sect. Gossypiospermum
37. Leaves never pellucid-punctate or -lineate; glands at leaf teeth (if leaves toothed) usually abaxial, torus-shaped, and persistent; disk glands present, globose, nectariferous; anther dehiscence extrorse; seeds exarillate 3837. Leaves usually pellucid-punctate or -lineate; glands at leaf teeth (if leaves toothed) usually marginal, conical or hair-like, and deciduous; disk glands absent or present, if present, in the shape of ligulate staminodes, not nectariferous; anther dehiscence introrse; seeds usually arillate 40
38. Leaf-like stipules (i.e., two "leaves" of different shape or size at a node) usually present; inflorescences spikes, racemes, corymbs, or fascicles; style 1; outer filamentous staminodes often present .... Azara38. Leaf-like stipules absent; inflorescences fascicles or short racemes; styles or style branches 1-7; outer filamentous staminodes lacking 39
42. Sepals fused into a tube, at least basally, usually more .... Samyda42. Sepals free.... Laetia
43. Stamens 5-12(-22), often included within the sepals .... Casearia43. Stamens 20-100, usually exposed 44
Notable genera and distinguishing features
- Abatia - opposite leaves, generally montane.
- Azara - commonly has leaf-like stipules, generally subtropical to temperate in the south.
- Banara - common genus, especially along rivers or in disturbed areas.
- Casearia - common genus, inflorescences usually axillary fascicles, leaves with pellucid -punctations or -lines, seeds arillate (sometimes confused with Xylosma, which lacks the pellucid-punctations, has unisexual flowers, and has free [and sometimes more numerous] stamens [visible as remnants even in fruit]; also, Casearia, when toothed, has deciduous conical leaf teeth ( Xylosma) typically has abaxial, persistent, glandular, doughnut or spherical shaped teeth).
- Hasseltia and Pleuranthodendron - common genera in Central America and northern South America; both have 3-veined leaves with paired glands at base of lamina or apex of petiole (see photo in Alford, 2003).
- Populus and Salix - generally temperate genera that have unisexual flowers in catkins, flowers have no evident calyx or corolla, and seeds have a coma: a specific structure with a circular bolster with unicellular cotton-like trichomes connected from below.
- Prockia - common genus, especially in disturbed or seasonally dry areas, 3-merous flowers.
- Xylosma - common genus, generally dioecious, occasionally with thorns or spines, flowers usually in axillary fascicles (see Casearia for confusion).
- Abatia (including Aphaerema) - Endemic
- Azara - Endemic
- Banara - Endemic
- Bartholomaea - Endemic
- Casearia - Native
- Dovyalis - Cultivated
- Euceraea - Endemic
- Flacourtia - Cultivated
- Hasseltia - Endemic
- Hasseltiopsis - Endemic
- Hecatostemon - Endemic
- Homalium - Native
- Laetia - Endemic
- Lunania - Endemic
- Macrohasseltia - Endemic
- Macrothumia - Endemic
- Neopringlea - Endemic
- Neoptychocarpus - Endemic
- Neosprucea - Endemic
- Olmediella - Endemic
- Pineda - Endemic
- Pleuranthodendron - Endemic
- Populus - Native, cultivated and naturalized.
- Prockia - Endemic
- Ryania - Endemic
- Salix - Native, cultivated and naturalized.
- Samyda - Endemic
- Tetrathylacium - Endemic
- Xylosma (including Priamosia) - Native
- Zuelania - Endemic
- Berberidopsis Hook.f. is treated under Berberidopsidaceae.
- Lacistema Sw. and Lozania Mutis ex Caldas are treated under Lacistemataceae.
- Cyanogenic (former) Flacourtiaceae are treated under Achariaceae.
- In general, tropical members of the family Salicaceae have few economic uses.
- The more temperate genus Populus is fast-growing, used for wood, and now includes the first woody species to have its entire genome sequenced.
- The mostly temperate genus Salix is one of the early sources of aspirin precursors.
- Salix species (willows) are very important in management of ecosystems such as prevention of erosion, bioremediation of soil and they provide a specialised habitat for other organisms.
- Some willows are widely cultivated as ornamental plants and used in wicker furniture.
- Both Salix and Populus are potential biofuel sources.
- In the Neotropics, genera like Casearia and Macrohasseltia are occasionally used for wood, and the genus Ryania has toxic compounds used in poisons and insecticides.
- Despite their lack of use in the Neotropics, Salicaceae are common elements of tropical forests.
Alford, M. H. 2003. Claves para los gιneros de Flacourtiaceae de Perϊ y del Nuevo Mundo. Arnaldoa 10(2): 19-38.
Argus, G.W. 1997. Infra-generic classification of Salix (Salicaceae) in the New World. Syst. Bot. Monogr. 52: 1-121.
Chase, M. W., S. Zmarzty, M. D. Lledo, K. J. Wurdack, S. M. Swensen, & M. F. Fay. 2002. When in doubt, put it in Flacourtiaceae: a molecular phylogenetic analysis based on plastid rbcL DNA sequences. Kew Bulletin 57: 141-181.
Eckenwalder, J.E. 1996. Systematics and evolution of Populus in: Stettler, R.F., Bradshaw, H.D., Heilman, P.E. & Hinckley, T.M. Biology of Populus and its implications for management and conservation 1(1): 7-32.
Gentry, A. H. 1993. A Field Guide to the Families and Genera of Woody Plants of Northwest South America (Colombia, Ecuador, Peru) with Supplementary Notes on Herbaceous Taxa. Chicago: University of Chicago Press.
Lemke, D. E. 1988. A synopsis of Flacourtiaceae. Aliso 12: 29-43.
Schneider, C. K. 1918. A conspectus of Mexican, West Indian, Central and South American varieties of Salix. Bot. Gaz. 65: 1-41.
Sleumer, H. O. 1980. Flacourtiaceae. Flora Neotropica No. 22. Bronx: New York Botanical Garden.
How to cite
Alford, M.H. & Belyaeva, I.V. (2009). Neotropical Salicaceae. In: Milliken, W., Klitgεrd, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Salicaceae.htm.
Click images to enlarge
Leaves, inflorescence and fruit of Abatia spicata (Peru) © Mac H. Alford, University of Southern Mississippi.
Habit, leaves and inflorescences of Banara guianensis (Ecuador) © Mac H. Alford, University of Southern Mississippi
Flower of Casearia javitensis (Ecuador) © Mac H. Alford, University of Southern Mississippi.
Leaves and fruit of Casearia nitida (U.S.A.) © Mac H. Alford, University of Southern Mississippi.
Leaves and inflorescence of Hasseltia floribunda (Costa Rica) © Mac H. Alford, University of Southern Mississippi.
Fruits of Hasseltia guatemalensis (Costa Rica) © Mac H. Alford, University of Southern Mississippi.
Leaves and fruit of Hasseltiopsis dioica (Costa Rica) © Mac H. Alford, University of Southern Mississippi.
Homalium guianense © Denise Sasaki, Projecto, Flora Cristalino.
Homalium guianense © Denise Sasaki, Projecto, Flora Cristalino.
Homalium guianense © Denise Sasaki, Projecto, Flora Cristalino.
Homalium guianense © Denise Sasaki, Projecto, Flora Cristalino.
Inflorescence of Neosprucea melastomatoides (Ecuador) © Mac H. Alford, University of Southern Mississippi.
Flowers and fruit of Pineda incana (Peru) © Mac H. Alford, University of Southern Mississippi.
Base of leaf (with glands) of Pleuranthodendron lindenii(Ecuador) © Mac H. Alford, University of Southern Mississippi.
Flower of Ryania speciosa (Peru) © Mac H. Alford, University of Southern Mississippi.
Male catkins of Salix discolor (U.S.A.) © Mac H. Alford, University of Southern Mississippi.
Flowers of Tetrathylacium macrophyllum (Ecuador) © Mac H. Alford, University of Southern Mississippi.
Flowers of Xylosma congesta (U.S.A.: cultivated) © Mac H. Alford, University of Southern Mississippi.
Branched thorns from trunk of Xylosma panamense (Costa Rica) © Mac H. Alford, University of Southern Mississippi.