Featured rare plant for May: Amorpha californica var. Napensis

Featured plant for May: Amorpha californica var. Napensis, Napa False Indigo. CNPS Rank 1B.2 (0.2 indicates moderately threatened).

We saw this plant at the Mark West Creek Regional Park on March 29, just starting to bud. I documented some observations of Napa False Indigo up in the Fountaingrove area of Santa Rosa in 2006, which you can see on Calflora.org. This deciduous shrub in the Pea family differs from the more widespread species by being glabrous instead of hairy with a smaller calyx lobe. It is listed in the CNPS Rare Plant Inventory, ranked as 1B.2, Plants Rare, Threatened or Endangered in California and Elsewhere, Moderately threatened in California. The Amorpha genus is host to the California Dogface Butterfly, the official state butterfly. In Sonoma county this plant can be affected by aggressive fire safely vegetation clearing in the urban wild interface. In fact, I am afraid that these particular plants have not survived, 20 years later, and are worth looking for. Napa False Indigo grows on dry brushy or wooded slopes, <4000 ft. Blooms April-July.

Here is a description and key of Amorpha. From ucjeps.berkeley.edu, the Jepson eFlora:

Habit: shrub, unarmed, gland-dotted.
Leaf: odd-1-pinnate; stipules bristle-like, ephemeral; leaflets with minute stipule-like appendages. Inflorescence: raceme, spike-like, terminal.
Flower: petal 1 (banner), +- purple; stamens 10, exserted, filaments fused near base; style puberulent.
Fruit: indehiscent. Seed: 1.

Species In Genus: +- 15 species: North America. Etymology: (Greek: deformed, from 1 petal)
Jepson eFlora Author: Steve Boyd & Duane Isely
Reference: McMahon & Hufford 2004 Amer J Bot 91:1219–1230
Unabridged Reference: Wilbur 1975 Rhodora 77:337–409

Key:
1. Main leaf axis without prickle-like glands; leaflet midrib generally ending as awn-like gland 0.5–1.5 mm ….. A. fruticosa 1′ Main leaf axis with prickle-like glands; leaflet midrib generally ending as sessile , head-like gland <= 0.5 mm ….. A. californica
2. Plant hairy; longest calyx lobe (except gland at tip) 1–2 mm ….. var. californica 2′ Plant ± glabrous; longest calyx lobe (except gland at tip) 0.5–1 mm – s NCoR, n SnFrB (Marin Co.) ….. var. napensis