Species: Astragalus purshii Dougl. ex Hook.

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Astragalus purshii Dougl. ex Hook.

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TAXONOMY

Family:

Fabaceae

Genus:

Astragalus

Species Synonyms:

Astragalus stragulus Fern.
Astragalus yukonis M.E. Jones
Astragalus bodinii var. yukonis (M.E. Jones) Boivin
Phaca bodinii (Sheldon) Rydb. ex Small

Common Names:

Pursh’s milkvetch
Pursh locoweed
woollypod milkvetch

DISTRIBUTION

Canada:

southern British Columbia – southern Alberta – southwestern Saskatchewan

Saskatchewan:

southwestern Saskatchewan; Great Sand Hills – Watrous

Ecoregion:

Cypress Upland, Mixed Grassland, Moist Mixed Grassland

HABITAT

Saskatchewan:

eroded, short grassland and mixed prairie

RARITY STATUS

Provincial Status According
to Harms (2003):

Threatened

Nature Conservancy Status:

G5 S2

Saskatchewan Species at
Risk Status:

Threatened

COSEWIC Status:

None

Astragalus purshii is threatened in Saskatchewan because it is rare or uncommon and somewhat regionally restricted in the province. Local population sizes vary. Possible threats have been identified for this species.

SPECIES DESCRIPTION

Roots:

taproot

Stems:

caudex branched; stems densely tufted, cushion-like or short and prostrate, usually < 5 cm tall, densely villous and tomentose

Stipules:

3 – 15 mm long, exceeding internodes, membranous

Leaves:

petiole slender; leaves 1 – 12 cm long, odd-pinnate, pubescence white, silky-villous

Leaflets:

5 – 17, elliptic to oval, silky-villous

Inflorescence:

peduncle 0 – 10 cm long; raceme short, 2 – 10-flowered

Flowers:

calyx tube 9 – 13 mm long, cylindrical; corolla ca 2 cm long, yellowish white; banner 19 – 26 mm long; wing 17 – 22 mm long; keel 15 – 21 mm long, purple-tipped; stamens 10, diadelphous; ovary superior

Fruits:

legume sessile, spreading, densely villous-tomentose; seeds 2 – 3 mm long, brown, often purple-spotted, smooth

ASTRAGALUS KEY FOR GENERA FOUND IN SASKATCHEWAN

1 Leaves needle-like, distinctly spine-tipped	A. kentrophyta var. kentrophyta
1 Leaves not needle-like or spine-tipped	2

2 Plants acaulescent, < 10 cm tall, densely caespitose; flowers often included among leaves	3
2 Plants caulescent, > 10 cm tall, stems evident, may be erect or decumbent (subacaulescent in A. missouriensis); flowers in distinct inflorescences	6

3 Leaves simple or with 1 or 2 linear leaflets	A. spatulatus
3 Leaves pinnate or trifoliate	4

4 Leaves trifoliate	A. gilviflorus var. gilviflorus
4 Leaves pinnate	5

5 Leaf pubescence dolabriform; leaflets 4 – 5x as long as wide, apex acute	A. lotiflorus
5 Leaf pubescence basifixed; leaflets 2x as long as wide, apex rounded	A. purshii var. purshii

6 Leaf pubescence dolabriform	7
6 Leaf pubescence basifixed	9

7 Corolla greenish-white or ochroleucus; plants green	A. canadensis var. canadensis
7 Corolla purplish; plants covered in greyish or silvery hairs	8

8 Leaflets up to 12 pairs; plants definitely caulescent; stipules connate	A. adsurgens ssp. robustior
8 Leaflets fewer than or equal to 7 pairs; plants subacaulescent; stipules distinct	A. missouriensis var. missouriensis

9 Petals yellow, cream or orange, keel occasionally blue-tinged	10
9 Petals blue, pink, or purple	18

10 Leaves and stems gray-hirsute, hairs 1 – 2 mm long, widely spreading	A. drummondii
10 Pubescence of leaves and stem variable but hairs shorter than 1 mm long	11

11 Pods glabrous or nearly to	12
11 Pods distinctly pubescent	15

12 Pods sessile or nearly so, stipe < 1 mm long; pods very fleshy, walls thick, hard and bony when dry	A. crassicarpus
12 Pods stipitate, stipe equal to or exceeding calyx; pods not fleshy, walls thin	13

13 Pods linear	A. racemosus var. racemosus
13 Pods broader	14

14 Leaflets 2 – 4 cm long; pods inflated and nearly terete	A. americanus
14 Leaflets < 2 cm long; pods very strongly compressed	A. tenellus

15 Flowers small, calyx tube 1.5 – 4.5 mm long, banner 4 – 12.5 mm long	16
15 Flowers large, calyx tube > 4.5 mm long, banner > 13 mm long	17

16 Pods pendulous, stipitate	A. alpinus var. alpinus
16 Pods erect, short-stipitate	A. bodinii

17 Leaflets without petiolules; pods sessile	A. pectinatus
17 Leaflets with petiolules; pods stipitate	A. agrestis

18 Pods 1 – 3 cm long	19
18 Pods generally less than 1.1 cm long	20

19 Pods with two deep grooves on upper side	A. bisulcatus
19 Pods lacking two deep grooves	A. flexuosus var. flexuosus

20 Pods spreading to erect	21
20 Pods spreading to deflexed	22

21 Flowers small, calyx tube < 4.5 mm long, banner < 13 mm long	A. bodinii
21 Flowers large, calyx tube > 4.5 mm long, banner > 13 mm long	A. agrestis

22 Pods plump	A. gracilis
22 Pods strongly compressed laterally	23

23 Racemes at most loosely 10-flowered; peduncles shorter than or only slightly surpassing leaves	A. vexilliflexus var. vexilliflexus
23 Racemes usually more than 10-flowered; peduncles longer than leaves	A. eucosmus