Bladder-senna
Colutea istria
Family: Fabaceae or Leguminosae
What it is like
Colutea istria is a deciduous Shrub growing to 3 m (9ft 10in). See above for USDA hardiness. It is hardy to UK zone 7. It is in flower from May to July. The species is hermaphrodite (has both male and female organs) and is pollinated by Bees. It can fix Nitrogen. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers dry or moist soil. The plant can tolerate maritime exposure.
Height (m): 3
Where it is found
Hard rock outcrops and wadis in shrub-steppes of Israel.
Middle East.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 0
Medicine
Rating: 0
Other
Rating:
Used in land reclamation projects in the Negev desert, consolidating soil and plant debris from flood waters. Plants can be grown as a hedge.
Hedge: Plants that can be grown as hedges.
Soil reclamation: Plants that can be grown in such circumstances an the spoil tips of mines in order to restore fertility.
Hedge: Hedge
Nitrogen Fixer: Plants that fix nitrogen in the soil
How it is grown
Requires a well-drained soil in full sun. Grows well on dry sunny banks and in poor soils. Dislikes strong winds, though another entry in the same book says that it tolerates salt-laden winds. This species is not very hardy in Britain, tolerating temperatures down to about -5°c, but it should succeed outdoors in the milder areas of the country. Even there it is probably best grown on a south or south-west facing wall. According to the International Legume Database, this species may actually be Colutea abyssinica Kunth & Bouch., a species found in N. Africa where it grows in montane grassland and shrubland. Flowers are produced on the current year's growth. Plants in this genus are notably resistant to honey fungus. 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.
Propagating it: Seed - pre-soak for 24 hours in hot water and sow late winter in a greenhouse. Scarification can help speed up the germination process. Germination can be slow and erratic, though treated seed usually germinates in 1 - 3 months at 20°c. As soon as they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out in late spring or early summer, after the last expected frosts. Cuttings of half-ripe wood, 7 - 10cm with a heel, July/August in a frame. Cuttings are not very long-lived.
Best place to grow: Woodland Garden Sunny Edge; Dappled Shade; Hedge;
Habit: Shrub
Hardiness: 6-9
Growth:
Soil: Light (sandy), medium, heavy (clay)
Shade: Semi-shade, no shade
Moisture: Dry, moist