Trees, to 10 m, armed, stipules spinescent. Stems usually erect to ascending, rarely scandent, young growth densely sericeous to woolly. Leaves alternate, even- or odd-pinnate; stipules present, caducous or persistent, 4–10 mm; petiolate; leaflets (8 or)9–21(–24), usually alter­nate, rarely opposite, stipels absent, blade margins entire, surfaces sericeous. Inflorescences 3–29-flowered, terminal, often congested into panicles; bracts present; bracteoles absent. Flowers papilionaceous; calyx zygomorphic, campanulate, lobes 5; corolla whitish to purplish, wing petals and keel tips usually purple; stamens 10, diadelphous; anthers basifixed; style glabrous proximally, with pollen brush surrounding distal 1/2; stigma terminal, capitate, ciliate. Fruits legumes, stipitate, terete, fusiform, elastically dehiscent, sparsely to densely stipitate-glandular, pubescent. Seeds 1 or 2(–5), spheroidal; hilum subapical. x = 9.

Distribution

sw United States, nw Mexico.

Discussion

Species 1.

Olneya is native to the Sonoran Desert in Arizona and adjacent California, and to north­western Mexico.

Olneya is readily distinguished from other woody papilionoid genera by the combination of broadly triangular calyx lobes, banner and wing petals tomentose abaxially, leaf rachises terminated by a spinose seta but that also usually bear an odd number of leaflets in alternate arrangement, and spinescent stipules that are especially prominent on the younger twigs.

Selected References

None.

Lower Taxa

Olneya tesota