Neotropical Juglandaceae

William Milliken

Royal Botanic Gardens, Kew, UK. 

Description

Trees, medium-sized to large.  Leaves pinnately compound with pinnate venation on the lamina, alternate or opposite, sometimes terminating with a single leaflet (Juglans  L.), indumentum of stellate hairs or peltate scales, commonly resinous and aromatic, basal leaflets often significantly smaller than terminal ones; stipules absent. Inflorescences terminal or axillary in the form of catkins, panicles, spikes or solitary flowers.  Flowers unisexual or hermaphrodite, petals absent, sepals 0-4. Male flowers subtended by fused bracts, with 4-100 basifixed sessile or subsessile anthers dehiscing by longitudinal slits. Female flowers with 2 stigmas and sometimes with staminodes, sepals fused to ovaryGynoecium syncarpous with 2 carpels.  Fruits are nuts enclosed by fleshy or winglike fused bracts/perianth, giving a samaroid or drupaceous appearance. Seeds one per fruit.

Notes on delimitation

Distribution in the Neotropics

  • In the Neotropics only one genus, Juglans L., is widespread from Mexico to Argentina. 
  • The others (Alfaroa Standl., Oreomunnea Oerst. and Carya Nutt.) are predominantly found in Mexico and Central America (with Alfaroa and Oreomunnea extending into Colombia).

Distinguishing characters (always present)

  • Trees with pinnately compound leaves and unisexual flowers with inferior ovary.
  • Gynoecium bicarpellate, with two styles.
  • Fruits one-seeded.

Other important characters

  • Aromatic and/or resinous leaves.
  • Margins of leaflets commonly serrate or serrulate.
  • Sometimes with chambered pith in the twigs (Juglans).
  • Male flowers in catkins, female flowers often on separate inflorescences.
  • Fruits with hard endocarp and ridges or wings.
  • Leaflets forming progression from larger terminal to smaller proximal.

Key differences from similar families

  • Although closely related to other members of the Fagales, this family is readily distinguished from all of them by its compound leaves.

Number of genera

Four genera:

  • Juglans
  • Alfaroa
  • Oreomunnea
  • Carya

Useful tips for generic identification

  • Juglans: alternate leaves, perianth of 4 sepals, androecium of 7-100 stamens, nut with complex internal structure surrounded by a ridged husk which dehisces, pith in twigs sometimes chambered.
  • Alfaroa: opposite leaves, perianth of 2 sepals, androecium of 6-12 anthers, nut without wings and without dehiscent husk.
  • Oreomunnea: opposite leaves, perianth of 2 sepals, androecium of 8-25 anthers, bracts and bracteoles fused into winglike (samaroid) structure around nut.
  • Carya: alternate leaves, perianth absent, 4 stamens in androecium, nut surrounded by a ridged husk which dehisces.

Key to genera of Neotropical Juglandaceae

1. Leaves opposite ... 2
1. Leaves alternate...3

2. Fruits with samaroid wings ... Oreomunnea
2. Fruits without samaroid wings ... Alfaroa

3. Perianth present in flower... Juglans
3. Perianth absent in flower... Carya

Status

  • Native.

General notes

  • Some species of Juglans and Carya produce high-quality timber. 
  • Several Juglans species also produce edible nuts.

Important literature

González, F. (2004). Juglandaceae.  pp 196-198 in: Smith, N.A. et al. (eds), Flowering plants of the Neotropics. Princeton University Press, New Jersey.

Manning, W.E. (1960). The genus Juglans  L. in South America and the West Indies. Brittonia 12(1): 1-26.

Manos, P. S. & Steele, K. P. (1997). Phylogenetic analyses of 'higher' Hamamelididae based on plastid sequence data. Amer. J. Bot.84:1407-1419.

Manos, P.S. & Stone, D.E. (2001).  Evolution, systematics and Phylogeny of the Juglandaceae.  Ann. Missouri Bot. Gard.88(2): 231-269.

Stone, D.E. (1972). New World Juglandaceae III. A new perspective of the tropical members with winged fruits.  Ann. Missouri Bot. Gard.59: 297-321.

How to cite

Milliken, W. (2009). Neotropical Juglandaceae. In: Milliken, W., Klitgĺrd, 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/Juglandaceae.htm.

Click images to enlarge


Alfaroa costaricensis Standl. (Davidse & Herrera 26193, Costa Rica) © William Milliken, RBG, Kew.



Fruit of Alfaroa costaricensis Standl. (Davidse & Herrera 26193, Costa Rica) © William Milliken, RBG, Kew.



Female flowers of Alfaroa costaricensis Standl. (Stone 2352, Costa Rica) © William Milliken, RBG, Kew.



Female flowers of Alfaroa costaricensis Standl. (Stone 2352, Costa Rica) © William Milliken, RBG, Kew.



Alfaroa guanacastensis Stone (Stone 3259, Costa Rica) © William Milliken, RBG, Kew.



Female flowers of Alfaroa guanacastensis Stone (Stone 3259, Costa Rica) © William Milliken, RBG, Kew.



Male flowers of Alfaroa guanacastensis Stone (Stone 3629, Costa Rica) © William Milliken, RBG, Kew.



Carya illoensis (Wang.) C. Koch (Manning & Manning 53363, Mexico) © William Milliken, RBG, Kew.



Fruit of Carya illoensis (Wang.) C. Koch (Manning & Manning 53363, Mexico) © William Milliken, RBG, Kew.



Carya illoensis (Wang.) C. Koch (Pringle 11177, Mexico) © William Milliken, RBG, Kew.



Fruit of Carya illoensis (Wang.) C. Koch (Pringle 11177, Mexico) © William Milliken, RBG, Kew.



Carya ovata (L.) K. Koch. var. mexicana (Manning & Manning 53332b, Mexico) © William Milliken, RBG, Kew.



Carya ovata (L.) K. Koch. var. mexicana (Manning & Manning 53332b, Mexico) © William Milliken, RBG, Kew.



Juglans australis Griseb. (Centurion & Quevedo 1208, Bolivia) © William Milliken, RBG, Kew.



Fruit of Juglans australis Griseb. (Centurion & Quevedo 1208, Bolivia) © William Milliken, RBG, Kew.



Juglans boliviana (C. DC.) Dode (Wood 12346, Bolivia) © William Milliken, RBG, Kew.



Flower of Juglans boliviana (C. DC.) Dode (Wood 12346, Bolivia) © William Milliken, RBG, Kew.



Fruit in section of Juglans boliviana (C. DC.) © William Milliken, RBG, Kew.



Juglans rupestris Engelm. (Pringle 1596, Mexico) © William Milliken, RBG, Kew.



Inflorescence of Juglans rupestris Engelm. (Pringle 1596, Mexico) © William Milliken, RBG, Kew.



Fruit of Oreomunnea pterocarpa Oerst. (Tonduz 18000, Costa Rica) © William Milliken, RBG, Kew.



Oreomunnea pterocarpa Oerst. (Tonduz 18000, Costa Rica) © William Milliken, RBG, Kew.



Fruit of Oreomunnea pterocarpa Oerst. (Lundy 1800, Costa Rica) © William Milliken, RBG, Kew.



Oreomunnea pterocarpa Oerst. (Lundy 1800, Costa Rica) © William Milliken, RBG, Kew.