Jepson Flora Project: Jepson Interchange    

link to manual TREATMENT FROM THE JEPSON MANUAL (1993) previous taxon | next taxon
Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California
For up-to-date information about California vascular plants, visit the Jepson eFlora.



John O. Sawyer, Jr.

Tree, shrub, monoecious
Stem: trunk < 35 m; bark ± smooth; lenticels present
Leaves simple, alternate, petioled, deciduous; stipules deciduous; blade ovate to elliptic, generally serrate, ± doubly so
Inflorescence: catkin, generally appearing before leaves, often clustered; bracts each subtending 2–3 flowers and 3–6 bractlets
Staminate inflorescence pendent, ± elongate
Pistillate inflorescence pendent or erect, developing variously in fruit (see key to genera)
Staminate flower: sepals 0–4, minute; petals 0; stamens 1–10; pistil vestigial or 0
Pistillate flower: sepals 0–4; petals 0; stamens 0; pistil 1, ovary inferior, chambers 2, each 1-ovuled, stigmas 2
Fruit: nut or nutlet, sometimes winged, subtended or enclosed by 1–2 bracts
Genera in family: 6 genera, 105 species: generally n hemisphere; some cultivated.



Tree, shrub
Stem: trunk < 35 m; bark smooth, gray to brown; twigs glabrous to finely hairy, reddish gray; lenticels small; winter buds stalked, 2-scaled
Leaf glabrous to finely hairy; blade 3–15 cm, elliptic to ovate, base ± truncate to tapered, sometimes subcordate
Staminate inflorescence 5–20 cm; bracts each subtending 3 flowers and 4 bractlets
Pistillate inflorescence 5–20 mm; bracts each subtending 2 flowers and 4 fused bractlets
Staminate flower: sepals 4; stamens 1–4
Pistillate flower: sepals 0
Fruits many, in cone-like catkin, bracts 3 mm, woody, winged
Species in genus: 30 species: n hemisphere, South America
Etymology: (Latin: alder)
Reference: [Furlow 1979 Rhodora 81:1–121, 151–248]
Root nodules contain nitrogen-fixing bacteria; wood used for interior finishing, to smoke fish, meats.

previous taxon | next taxon
bioregional map for ALNUS being generated
YOU CAN HELP US make sure that our distributional information is correct and current. If you know that a plant occurs in a wild, reproducing state in a Jepson bioregion NOT highlighted on the map, please contact us with that information. Please realize that we cannot incorporate range extensions without access to a voucher specimen, which should (ultimately) be deposited in an herbarium. You can send the pressed, dried collection (with complete locality information indicated) to us (e-mail us for details) or refer us to an accessioned herbarium specimen. Non-occurrence of a plant in an indicated area is difficult to document, but we will especially value your input on those types of possible errors (see automatic conversion of distribution data to maps).

Retrieve Jepson Interchange Index to Plant Names entry for Alnus
Retrieve dichotomous key for Alnus
Overlay Consortium of California Herbaria specimen data by county on this map
Show other taxa with the same California distribution | Read about bioregions | Get lists of plants in a bioregion
Return to the Jepson Interchange main page
Return to treatment index page
  • This page is no longer being maintained.

University & Jepson Herbaria Home Page |
General Information | University Herbarium | Jepson Herbarium |
Visiting the Herbaria | On-line Resources | Research |
Education | Related Sites
Copyright © by the Regents of the University of California