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:

none

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

Pursh’s milkvetch 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-creeping, usually < 5 cm tall, densely long-hairy and woolly

Stipules:

3 – 15 mm long, exceeding internodes, membranous

Leaves:

stalk slender; leaves 1 – 12 cm long, odd-pinnate, hairs white and silky

Leaflets:

5 – 17, elliptic to oval, silky hairy

Inflorescence:

unbranched, short, 2 – 10-flowered; inflorescence stalk 0 – 10 cm long

Flowers:

sepal tube 9 – 13 mm long, cylindrical; petals 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, 9 + 1 arrangement; ovary superior

Fruits:

pod sessile, spreading, densely long-hairy and woolly; 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 without a distinct stem, < 10 cm tall, densely tufted; flowers often included among leaves	3
2 Plants with a distinct stem, > 10 cm tall, may be erect or creeping, stem not well defined in A. missouriensis; flowers in distinct inflorescences	6

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

4 Leaves with 3 leaflets	A. gilviflorus var. gilviflorus
4 Leaves pinnate

5 Leaf hairs attaching in the middle, with one side longer than the other; leaflets 4 – 5x as long as wide, tip acute	A. lotiflorus
5 Leaf hairs attaching at the base; leaflets 2x as long as wide, tip rounded	A. purshii var. purshii

6 Leaf hairs attaching in the middle, with one side longer than the other	7
6 Leaf hairs attaching at the base	9

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

8 Leaflets in up to 12 pairs; plants with a definite stem; stipules fused	A. adsurgens ssp. robustior
8 Leaflets fewer than or equal to 7 pairs; stem not well-defined; stipules not fused	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-hairy, hairs 1 – 2 mm long, widely spreading	A. drummondii
10 Hairs of leaves and stem variable but hairs shorter than 1 mm long	11

11 Pods hairless or nearly to	12
11 Pods distinctly hairy	15

12 Pods sessile or nearly so, stalk < 1 mm long; pods very fleshy, walls thick, hard and bony when dry	A. crassicarpus
12 Pods stalked, stalk equal to or exceeding sepals; 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 round in cross section	A. americanus
14 Leaflets < 2 cm long; pods very strongly flattened	A. tenellus

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

16 Pods hanging down, stalked	A. alpinus var. alpinus
16 Pods erect, short-stalked	A. bodinii

17 Leaflets without stalks; pods sessile	A. pectinatus
17 Leaflets with stalks; pods stalked	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, sepal tube < 4.5 mm long, banner < 13 mm long	A. bodinii
21 Flowers large, sepal tube > 4.5 mm long, banner > 13 mm long	A. agrestis

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

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