Fraxinus. OLEACEAE (Olive family)

Key choices: Group 5. Trees with leaves opposite or whorled
1. Leaves compound ...
2'. Leaves pinnately compound ...
3'. Leaflets usually 5 or more, toothed or not; fruit various but not a 2-winged samara ...
6'. Leaves once-divided ...
8'. Lflts 5 to 13, usually not unequal at base; fruit a dry, 1-seeded winged samara ... Fraxinus

Fraxinus americana. WHITE ASH. Eastern United States.

Pinnate leaves about 10 inches long with five leaflets, smooth green on top and pale and possibly furry underneath. The fruit is a hanging winged seed 1 or 2 inches long. There is a large one west of Encina Commons off Galvez Mall (planted in the 1890s), one at the south end of Lasuen Street on the side toward the Oval, and others in the vicinity.

Illustration: habit

Name derivation: Classical Latin name for ash | American

Fraxinus angustifolia 'Raywood' (Fraxinus oxycarpa). RAYWOOD ASH. Southern Europe to Western Asia, North Africa

The narrow-leaved ash exists in several horticultural varieties of which 'Raywood' is best known locally. In summer, bunches of yellow samaras add color. In the fall, the leaves rather resemble those of the Chinese pistache but differ by having finely saw-toothed leaflets, darker above, with palpable midrib and veins. Examples may be seen at Rains Houses at the north end of the semicircular lawn, nearby at the north end of Hacienda Commons, and on the parking lot side of the Haas Public Service Center. In Menlo Park, three trees are at 1885 Oakdell Drive, and in Palo Alto two trees are at 1440 California Avenue, between Columbia and Dartmouth Streets.

Detail of leaflets of the odd-pinnately compound leaf of Raywood ash. Odd-pinnately compound signifies a single leaflet at the end of the leaf axis (rachis) of a pinnately-compound leaf, as shown in the illustration right. Even-pinnately compound, as is the usual case, say, for chinese pistache, signifies a pinnately-compound leaf terminating in a pair of leaflets. The compound leaves of ashes are opposite, two opposing leafs at each node, while those of pistache are alternate, one leaf per node.

Name derivation: Classical Latin name for ash | narrow-leaved

Fraxinus excelsior. EUROPEAN ASH. Europe, Turkey

The hard and resilient wood of the ash suits it for axe handles, skis, tennis racquets, ladders, and similar uses, making it one of the most valuable trees in European forest production. It may be distinguished from the other ashes on campus by the relatively long strings of samaras which themselves are long, being about 1½ inches. At the outer end of the single wing there is a tiny notch. The oval leaflets are 7 to 11 in number, about 4 inches long, with a toothed margin. They are dark glossy green on top but pale underneath and with some slight furriness on the midribs of the leaflets. If a leaf is pulled from the tree in summer the leaflets curl tightly. The next season's leaf buds, which are already well-formed early in summer, are black. A dozen European ash stand in the large parking lot at Jordan Quad.In Spain the name of this tree is fresno.

Virgil says, Fraxinus in silvis pulcherrima, pinus in hortis, populus in fluviis, abies in montibus altis. The ash is the most beautiful tree in the woods, the pine in gardens, the poplar by rivers, and the fir on high mountains."

Name derivation: Classical Latin name for ash | taller

Fraxinus latifolia. OREGON ASH. Pacific Coast

Oregon ash is a major timber tree in the coastal forests north of the border with Oregon, but is also native in a spreading form to the neighborhood of Palo Alto. The leaves, up to 12 inches long, may have five to seven leaflets of which the terminal leaflet is longest and may be 6 inches long. The margins are wavy, but practically without teeth, and the side leaflets may be stalkless. Samaras are borne on female trees and are about 1-1/2 inches long. Several large rough-barked trees at the corner of Roth Way and Lasuen Street may be Oregon ash.

Name derivation: Classical Latin name for ash | broad-leaved

Fraxinus ornus. FLOWERING ASH. Southern Europe, Asia Minor

An unusual tree here and not showy. The smooth pinnate leaves are about 8 inches long with seven leaflets, some fuzz on the midrib, and flowers with four petals. See a specimen east of Memorial Church behind Building 50 (removed Autumn 2011), near the southeast corner of Roth Way and the Oval growing in the drainage ditch, and in Palo Alto at the house at 1102 Channing Avenue, the first street tree around the corner on Harriet Street.

Name derivation: Classical Latin name for ash | Latin name for the mountain ash

Fraxinus uhdei. SHAMEL ASH. Mexico

This is a large timber tree from Mexico and, as with the Chinese elm and other deciduous trees grown in mild climates, may not drop its leaves in the fall. At Stanford in spring there is a conspicuous difference between the fully leaved Shamel ashes and the burgeoning Modesto ashes. Later in the summer it may be hard for a casual observer to distinguish our two most common ashes. Shamel ash leaflets are generally more numerous (five to nine as against three to five), a darker green and longer (4 inches as against 3). The leaf margins are also different.

There are eight large Shamel ash in front of the Bookstore, three of which are male trees (the two on the west and the one closest to the Post Office). On the females, samaras about an inch long will be found hanging inconspicuously in the foliage in spring. By October several of the female trees are heavy with brown fruit and few leaves, and by November there is voluminous but inoffensive litter. The presence of both male and female trees tells us we are not dealing with a cloned variety, as with Fraxinus velutina ‘Modesto’. The Shamel ash was introduced in Riverside by Dr. Archie Shamel about 1925. In Palo Alto, an old giant is at 1636 Edgewood Drive at the corner of Patricia Lane

Name derivation: Classical Latin name for ash | honors Carl Uhde, German plant collector who explored eastern Mexico 1844-1848.

Fraxinus velutina 'Modesto'. MODESTO ASH. United States, Mexico

This deciduous smooth-trunked tree has 6-inch leaves with five leaflets that are furry underneath. It also has velvety branchlets. There may be specimens of the wild species on campus, but the cultivar 'Modesto' has been widely used. The cloned trees are male; consequently, no winged seed contributes to the litter, not that its absence is very noticeable amidst the copious leaf fall. A good group can be seen on the avenue (formerly known as Via Crespi) between Green Earth Sciences and the Durand Building. Others are to the northwest of Herrin Hall (Biology), west of Old Chemistry, and on the south side of Escondido Mall near Mitchell Earth Sciences. It is used as a street tree in Palo Alto, including Greer Road between California Avenue and Amarillo Avenue.

The ash is one of the last trees to come into leaf in the spring (Chinese pistache, linden, catalpa, and silk tree are others), often delaying two months behind the plum trees, and when in leaf casts a relatively thin shade, letting through a luminous green light. As the Modesto ash often succeeds where other species fail, vast numbers have been planted in California. But the Modesto clone has come under attack by a mutilating disease that leaves the trees partially defoliated through the summer. Consequently, disease is a serious economic matter. This experience points up the need for diversity: new species, as well as new clones.

Illustrations: modesto ash, Escondido Mall, 12/7/03 | compound leaf

Name derivation: Classical Latin name for ash | velvety, referring to the underside of the leaves.

Related material: Canopy Trees for Palo Alto Tree Library

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