A shrub to small tree, densly branched, 10 to 20 feet tall (rarely taller), smoketree has bark that is soft and pale grey. Stiff silvery branches with tiny dark glands end in sharp pointed tips. Most of the year smoketree is leafless, although leaves will emerge with rains or well watered situations. A rapid grower under favorable conditions, it is believed that trees are relatively short-lived though no studies have confirmed this myth. Plants that are not well watered are slower-growing. A stem photosynthetic, twigs and young limbs carry on majority of photosynthesis.Smoke tree has a deep rootsystem. Young plants develop extensive root systems soon after the seed germinates.
Flowers with deep indigo to blue pea-like corollas, borne in racemes, making whole tree indigo in blooming season. February through November flowering occurs, and the peak is May into July. Flowering may be observed in 2-3 years after germination, under favorable conditions. Blooming is dependable except in the driest of years In greenhouse conditions plants have flowered at 8 months old. Flowering is followed by single seeded pods with smooth seeds having mottled grey and brown seed coats.
Habitats include arroyo habitats in arid regions of Sonoran Desert, sandy and gravelly soils of arroyo margins and channels in W. Arizona, S. California, NE Baja california, and extreme NW Sonora from 210 feet below sea level, to 2300 feet above although the higher populations are rare. Smoke tree is from areas with hot arid summers and mild winters with winter rainfall. They can also be found at roadsides. During heavy rains flowing water most likely scours seeds and provide the moisture for germination. Seeds fall throughout the summer, especially July. They fall from the plant soon after ripening.They remain under the plant until carried away by ants, rodents, or washed away by storms. Smoke tree will set viable seeds if pollinated with its own pollen. Rain in the warm seasons is not as dependable as winter rains but are more important for seedling establishment. This plant can be pushed to grow fast, but usually is a moderate grower. Growth depends on treatment of the plant.
Usually smoke tree forms pure stands but sometimes grows with blue palo verde (Cercidium floridum), ironwood (Olneya tesota), honey mesquite (Prosopis glandulisa var. Torreyana), catclaw acacia (Acacia gregii), desert willow (Chilopsis linearis), and desert lavender (Hyptis emoryi), some areas it is associated with the introduced and troublesome salt ceder (Tamarix ramosissima). Smoke tree forms a high contrast to rest of sparse landscape and its more green colors, especially when in bloom with its indigo flush of bloms. Bees are attracted to the flowers.
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