Oleaceae – Olive Family

Only a few trees are represented in this work, but a comprehensive field guide of Willamette Valley wetland prairies would be remiss to leave out Fraxinus latifolia (Oregon Ash) from the Oleaceae (Olive) family. Oleaceae includes much more than water loving ash trees though, Lilacs, Forsythia, and, of course, Olives are all commonly planted or economically valued members of this woody tree and shrub family.[1] Although seeming dissimilar, these 24 genera and 615 species, share a number of structural characteristics.[2] Leaves are opposite and can be simple (as in Lilacs) or compound and pinnate (ex. Oregon Ash) and can sometimes have square-ish stems. Flowers have four united sepals and four united petals, with two stamens and superior ovaries. Fruits mature into capsules, winged seeds (samaras), or drupes (fleshy fruits with hard pits) as in olives.  For thousands of years olives have been the most important oil producing plant in the world. Brought into cultivation around 7,000 b.c.e., Olea europea, was once a wild plant found on the edge of the Persian desert, but is now almost impossible to find in its truly undomesticated form.[3]

Fraxinus latifolia – Oregon Ash

 

Species Code: FRLA

Habit: Medium sized, deciduous, dioecious trees growing 10 to 35 m tall with thick, gray-brown bark.[4]

 

Leaves: Pinnately compound, deciduous leaves are oppositely arranged along branches. Leaves are made up of 5 to 7, bright green, oval leaflets that sharply taper at both ends and grow up to 13 cm long.[5]

 

Flowers: Inflorescences are dioecious panicles made up of inconspicuous, tiny flowers segregated by sex to different trees. Male flowers are yellow, while female flowers appear green. Both develop well before leaves in Spring, bunched in clusters on twigs.

 

Fruits: Single seeded winged fruits known as samaras that are 3 to 5 cm long growing in dense clusters on female trees. Similar to maple tree samaras, but cut in half.[6]

 

Ecology: Facultative Wetland Species (FACW),[7] found growing in standing water, vernal pools, stream or pond edges.[8]

 

 

[1] Elpel, T. J., Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, 2004. 134

[2] Simpson, M. Plant Systematics 2^nd ed. Academic Press, Burlington, MA. 406

[3] Langenheim Jean H. Botany: Plant Biology and its Relation to Human Affairs. John Wiley and Sons, NY. 1982.

[4] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001. 318

[5] Pojar, J., Mackinnon, A., Editors Plants of the Pacific Northwest Coast. Lone Pine Publishing, Vancouver, Canada. 2004. 50.

[6] Pojar, J., Mackinnon, A., Editors Plants of the Pacific Northwest Coast. Lone Pine Publishing, Vancouver, Canada. 2004. 50.

[7] USDA Plants Database: < https://plants.usda.gov/core/profile?symbol=FRLA >

[8] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001. 107.