Astragalus gummifer
| Astragalus gummifer | |
| Light: |  |
| Moisture: |  |
| Hardiness: | 8 |
| Soil pH: | 5.6-8.4 |
| Evergreen | |
| Height: | 1' |
| Width: | 1' |
| Native to: | |
| Nitrogen Fixer | |
| Edible Rating: |  |
| Medicinal Rating: |  |
| Tea: | Yes |
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Astragalus gummifer (common name: tragacanth)
Propagation: Seed - best sown as soon as it is ripe in a cold frame[1]. A period of cold stratification may help stored seed to germinate[1]. Stored seed, and perhaps also fresh seed, should be pre-soaked for 24 hours in hot water before sowing - but make sure that you do not cook the seed[2][1]. Any seed that does not swell should be carefully pricked with a needle, taking care not to damage the embryo, and re-soaked for a further 24 hours[2][1]. Germination can be slow and erratic but is usually within 4 - 9 weeks or more at 13°c if the seed is treated or sown fresh[2]. As soon as it is large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter, planting them out into their permanent positions in late spring or early summer, after the last expected frosts.
Cultivation: Requires a dry well-drained soil in a sunny position[3][4]. Succeeds in poor soils[1]. Tolerates a pH in the range 3.2 to 7.8.
This species is not hardy in the colder areas of the country, it tolerates temperatures down to between -5 and -10°c[4]. Whilst it is likely to tolerate low temperatures it may not be so happy with a wet winter.
Plants are intolerant of root disturbance and are best planted in their final positions whilst still small[1].
This plant is a sub-shrub and although it produces woody stems these tend to die back almost to the base each winter.
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[1]. Many members of this genus can be difficult to grow, this may be due partly to a lack of their specific bacterial associations in the soil[1].
Range: W. Asia - Iraq, Kurdistan
Habitat: Dry sub-alpine slopes and valleys, occasionally below the tree line, 1200 - 2600 metres in Iraq[5]. Upland forests and grassland[4].
Edibility: A source of a high quality gum tragacanth - used as a thickener in confections, salad dressings, sauces etc[6][7][8][9][10][5]. It is an approved additive to food and has the E number E413[4]. Some of the gum exudes naturally from the root and from damaged stems[11], more can be obtained by incision of the stem about 5cm below ground level[9].
Medicinal: The gum obtained from the root and stem is demulcent, though it is not often used internally because it is not completely soluble[7]. This gum has recently been shown to stimulate the immune system and to suppress tumours[4]. The gum has long been employed externally as a dressing for burns and is also used in lozenges in order to bind the ingredients and impart consistency to the product[7].
Usage: Gum tragacanth is obtained from the stem (see above). It has a wide range of uses including:- a thickening agent in preparing dyes for calico printing, textile dyes and for dressing fabrics, it is also a thickener in making glues, water colours, ink (where it supplies a gloss), it is a binding agent in paper making, a culture medium in laboratories etc[9][12].
Both the stems and the gum can be burnt as a fragrant incense[13].
Pollinators: Bees, lepidoptera
Soil: Can grow in light and medium soils.
Drainage: Prefers well drained soil.
Flower Type: Hermaphrodite
Known Hazards: Many members of this genus contain toxic glycosides[14]. All species with edible seedpods can be distinguished by their fleshy round or oval seedpod that looks somewhat like a greengage[15]. A number of species can also accumulate toxic levels of selenium
Links
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Huxley, Anthony. The New Royal Horticultural Society Dictionary of Gardening. MacMillan Press, 1992.
- ↑ 2.0 2.1 2.2 Rice, Graham. Growing from Seed Volume 2. Thompson and Morgan, 1988.
- ↑ Chittendon, Fred. RHS Dictionary of Plants. Oxford University Press, 1951.
- ↑ 4.0 4.1 4.2 4.3 4.4 Bown, Deni. Royal Horticultural Society Encyclopaedia of Herbs and Their Uses. Dorling Kindersley, 1995.
- ↑ 5.0 5.1 Chakravarty, Hiralal. The Plant Wealth of Iraq. 1976.
- ↑ Hedrick, Ulysses. Sturtevant's Edible Plants of the World. Dover Publications, 1972.
- ↑ 7.0 7.1 7.2 Grieve, Margaret. A Modern Herbal. Penguin, 1984.
- ↑ Schery. Robert. Plants for Man. Prentice Hall, 1972.
- ↑ 9.0 9.1 9.2 Howes, Frank. Vegetable Gums and Resins. Chronica Botanica, 1949.
- ↑ Tanaka, Tyōzaburō. Tanaka's Cyclopaedia of Edible Plants of the World. Keigaku Publishing, 1976.
- ↑ Hill, Albert. Economic Botany. The Maple Press, 1952.
- ↑ Komarov, Vladimir. Flora of the USSR. Gantner Verlag, 1968.
- ↑ Genders, Roy. Scented Flora of the World. Robert Hale, 1994.
- ↑ Frohne, Dietrich and Hans Pfänder. J. A Colour Atlas of Poisonous Plants. Timber Press, 1984.
- ↑ Harrington, Harold. Edible Native Plants of the Rocky Mountains. University of New Mexico Press, 1967.