| Olneya | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Fabales |
| Family: | Fabaceae |
| Subfamily: | Faboideae |
| Tribe: | Robinieae |
| Genus: | Olneya A.Gray |
| Species: | O. tesota |
| Binomial name | |
| Olneya tesota | |
 | |
| Natural range | |
| Synonyms[2] | |
TesotaMüll.Berol., W.G.Walpers, Ann. Bot. Syst. 4: 479 (1857) | |
Olneya tesota is aperennial floweringtree of the familyFabaceae, legumes (peas, beans, etc.), which is commonly known asironwood,desert ironwood, orpalo fierro in Spanish. It is the only species in themonotypic genusOlneya. This tree is part of the westernSonoran Desert in Mexico and United States.
The desert ironwood grows as abush ortree, reaching heights of about 10 metres (33 feet) and average trunk diameters of about 60 centimetres (24 inches). Exceptionally, in larger protected washes it can reach greater height and a more massive trunk.
In younger trees, the bark is gray, shiny, and smooth; in older trees the bark is broken open. The tree isevergreen, but can lose itsleaves if temperatures fall below 2 °C (36 °F). In continual drought conditions the leaves will be lost.
The leaves are bluish-green and pinnately compound. They are arranged on apetiole, 15 cm (6 in) long, with 6–9 leaflets (or variously up to 15, with 7 opposite and one terminal), each measuring 0.7 to 2.5 cm (1⁄4 to 1 in). At the base of each pinnate leaf petiole grow two thorns, each about1 cm (3⁄8 in) long.
Bloom time occurs in late April/May to June. Flowers are of 5 unequal petals, in colors of medium purple, magenta-red, or white to pale pink. Seedpods are 5–8 cm (2–3 in) long and light reddish brown when seedpods have ripened.
Two other species,Parkinsonia florida (blue palo verde) andAcacia constricta (catclaw acacia), have similar light red/brownish seedpods. Catclaw acacia's seedpods are shorter andJ-shaped.
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The genus name ofOlneya is in honour ofStephen Thayer Olney (1812–1878), who was an American manufacturer andbotanist with expertise in the genusCarex.[3][4]
The genus wascircumscribed byAsa Gray in Pl. Nov. Thurb. page 328 in 1854.[2]
The species is native to theSouthwestern United States and extreme northwestern Mexico in theBaja California Peninsula and theSonoran Desert. Within Mexico its range includes the states ofBaja California Sur andBaja California, on theGulf of California side east of the cordillera ranges, andSonora state west of theSierra Madre Occidental cordillera, in the south approaching the northern border of northernSinaloa state. In the Southwestern US its range includes theColorado Desert of southeastSouthern California, a part of the Sonoran Desert, and western and southernArizona.[2]Olneya does not range into the higher-elevation, colder, southeast of Arizona's Sonoran Desert region, nor into thesky islands of theMadrean Sky Islands region.
The pleasant-tasting sap is consumed by bees and hummingbirds. Thesilky-flycatcher orphainopepla pose a problem, for when they consume mistletoe berries and excrete them in the cracks ofOlneya tesota, the mistletoe will parasitize its host.[5]
Olneya tesota is anindicator species of the Sonoran Desert region.[6] The Sonoran Desert has one other species with the identical north–south, and east–west range. The seasonally migratinglesser long-nosed bat follows the bloom season of various species from south to north and extends into the same regions of the Sonoran Desert asOlneya. The bat ranges from southern Baja California del Sur and north into the Southwestern US.[7]
In the north, both species define the Colorado Desert sub-region of the Sonoran Desert surrounding the northern end of the Gulf of California; further south in the Baja Peninsula the sub-division is defined as the Vizcaino Desert.
The winter and permanent range of the bat extend into the northern countries ofCentral America.
The seeds can be eaten by first being roasted.[8]
Olneya ironwood is very hard and heavy. Its density is greater than water and thus sinks; it does not float downstream in washes and must be moved by current motion.
Due to its considerable hardness, processing desert ironwood is difficult. Final treatment of the wood with solutions can also be difficult because of its high density. As a result, mass processing of this wood is difficult, and most of its commercial usages are artisanal, such asdurable wooden sculptures as well asknife handles.
Ironwood Forest National Monument in south-central Arizona is named forO. tesota.
