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Senna armata (S. Watson) Irwin & Barneby

Cassia armata S. Watson

Spiny senna, desert senna

KingdomPlantaePlants, but not fungi, lichens, or algae
SubkingdomTracheobiontaVascular plants—plants with a “circulatory system” for delivering water and nutrients
DivisionMagnoliophytaFlowering plants, also known as angiosperms
ClassMagnoliopsidaDicotyledons—plants with two initial seed leaves
SubclassRosidaeRoses, legumes, proteas, dogwoods, hydrangeas, mistletoes, euphorbias, grapes, many more
OrderFabalesLegumes (pea and bean families)
FamilyFabaceaeLegume family (peas and beans)
GenusSennaFrom the Arabic name Sana
SpeciesarmataSpiny or thorny, literally “armed”

About plant names...

Spiny senna is native to the North American southwest, a shrub with a dense tangle of sharp-tipped branches. They are leafless for most of the year, so when they aren’t flowering they look like someone gathered a heap of kind­ling and forgot about it. When they are flowering, it looks like someone lit it. They are found at elevations of 328-4593' (100-1400 m), in sandy or gravelly washes.

Plants: Shrubs up to 3' (1 m) in height. They are densely branched, and many of the branches terminate in sharp spines. Tiny tubular hairs reflect the sun’s heat.

Leaves: Leaves are on narrow branchlets, in 2-4 opposite pairs. Each leaflet is ⅛-³/₁₆" (4-6 mm) around, and ovate. Leaf pairs aren’t quite symmetric. Leaves are dropped entirely most of the time, in order to conserve water.

Flowers: Yellow, or salmon pink, occurring singly or in clusters in leaf axils. Each flower has five petals, and is ⅝-⅞" (1.6-2.4 cm) in diameter. Flower petals are not evenly distributed, so the flower has bilateral symmetry but not radial symmetry. Flowers appear from March to July.

Fruits: Pods are ⅞-1½" (2.5-4 cm) long, straight, and con­tain a few seeds.

 

Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park, CA

Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park, CA

Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park, CA

Here are some similar species:
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Senna armata

Encelia farinosa
Common Name

spiny senna

brittlebush
Plant Shrubs up to 3' (1 m) in height. They are densely branched, any many of the branches terminate in sharp spines. Forms rounded bushes 12-59" (30-150 cm) high.
Flowers Yellow, or salmon pink, occurring singly or in clusters in leaf axils. Each flower has five petals, and is ⅝-⅞" (1.6-2.4 cm) in diameter. Flower petals are not evenly distributed, so the flower has bilateral symmetry but not radial symmetry. Flowers appear from March to July. Yellow flower stalks extend outward from the domelike bush. Each flower is 1-1¼" (3-3.5 cm) around. Each is a composite flower, comprised of a central disc with many yellow or purple-brown disc florets, and yellow or orange-yellow ray florets.
Leaves Leaves are on long and narrow branchlets, in 2-4 opposite pairs. Each leaflet is ⅛-³/₁₆" (4-6 mm) around, and ovate. Leaf pairs aren’t quite symmetric. Leaves are dropped entirely most of the time. Leaves are triangular (ovate to deltoid), blue-gray, and 1-3" (3-8 cm) long. Fine matted plant hairs on the leaves give them a silvery appearance.
Fruit Pods are ⅞-1½" (2.5-4 cm) long, straight, and con­tain a few seeds. ¹/₁₆-³/₁₆" (3-6 mm).
Range/ Zones

Habitats In sandy or gravelly washes, at elevations of 328-4593' (100-1400 m). Dry, gravelly slopes and open sandy washes, at elevations up to 3281' (1 km).
Type Wild Wild

 

Online References:

Senna armata at Bird and Hike

Senna armata on www.americansouthwest.net

Senna armata at the Anza-Borrego Desert Natural History Association

Senna armata on CalPhotos (Photos)

Senna armata on Wikipedia

Senna armata on Discover Life

Senna armata on www.desertwildflower.com

Senna armata from the Jepson Manual

Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park, CA
≈ 4 × 6" (11 × 16 cm)

Senna armata (spiny senna, desert senna)

2/28/2010 · Anza-Borrego Desert State Park, CA
≈ 12 × 8" (31 × 20 cm)

Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park, CA
≈ 4½ × 7" (12 × 18 cm)

Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park, CA
≈ 4 × 6" (11 × 16 cm)

Senna armata (spiny senna, desert senna)

2/28/2010 · Anza-Borrego Desert State Park, CA
≈ 31 × 21" (78 × 52 cm)

Senna armata description by Thomas H. Kent, last updated 25 May 2020.

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Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park
≈ 12 × 8" (31 × 20 cm)

Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park
≈ 5 × 3½" (13 × 9.2 cm)

Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park, CA
≈ 4 × 6" (10 × 15 cm)

Senna armata (spiny senna, desert senna)

5/2/2018 · Pinto Basin Road, Joshua Tree National Park, CA
≈ 4 × 6" (11 × 16 cm)

Senna armata (spiny senna, desert senna)

2/28/2010 · Anza-Borrego Desert State Park, CA
≈ 21 × 14" (52 × 34 cm) ID is uncertain

Range:

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