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Blackwood, Iron Wood, Yellow Cassia, Thailand Shower, Siamese Cassia

Senna siamea



This non-nitrogen fixing leguminous tree is native to Southeast Asia. It is now cultivated throughout the tropics.


This tree is known for its hard wood which is used for furniture, poles, mulch, charcoal, and firewood, though when burned it tends to produce a lot of smoke. The tree is also used for erosion control, land reclamation in former tin mining sites, shade for tea, cocoa, and coffee plantings, as a windbreak and in agroforestry when planted among other crops. Bees are attracted to the flowers for their nectar secretion. The foliage can be used as a green manure or fodder for cattle, sheep, and goats. When heavily pruned, the Cassod Tree will respond by resprouting. The leaves are toxic to poultry and swine. The young leaves can be used in curry dishes.


The seeds can be direct seeded or sown in trays and transplanted to containers. Seedling growth is best with loose soil, moisture and full sunlight. Seeds need to be planted at a depth of 0.5-1.0 cm (1/4 in-1/2 in) and in direct sunlight to germinate. In arid areas, plants should be transplanted when they are 30 cm (12 in) tall. The seedlings are thinned at the end of the first rains. For fuelwood, the trees should be planted 3-8 cm (1 in-3 in) apart. For alley cropping, the trees should be 25-40 cm (10 in-16 in) apart. The Cassod Tree performs best in a monsoon climate in the lowland tropics with rainfall between 500-2800 mm (20 in-100 in) and temperatures of 21o-30° C (70°-85° F).

Even during 4-8 months of drought, this shallow-rooted tree needs to be in contact with groundwater. The Cassod Tree does not grow well above 1300 m (4500 ft), and will not survive temperatures below 10° C (50° F). It grows best in well-drained, fertile soils on river banks. In semi-arid regions with 500-700 mm of rainfall (20 in-25 in), it will grow if the dry season does not exceed 4-6 months and the roots have groundwater available.

Harvesting and Seed Production

Trees grown for firewood can be harvested in 5-7 years reaching heights of 10-12 m (35 ft-40 ft). After one year, trees used for mulch and leaf production can be cut 3-4 times per year. This cassia produces many seed pods with 20 seeds in each. Mature pods, may be collected when they hang twisted in clusters and have turned to yellow-brown. There are about 37,000 seeds per kilogram. Seed pods should be allowed to dry in the sun for a few days until they release their seeds. Store seeds in an airtight container in a cool spot for up to one year. Germination of older seeds will be hastened by dipping them in hot water for one minute and removing them. Twenty-four hours later, they may be planted.

Pests and Diseases

No significant pest or disease damage has been recorded. Fungus will occasionally attack the roots and minor damage can be caused by the wood rot/mushroom, Ganoderma lucidum. Browsing animals and wildlife eat the leaves of this tree.

Cooking and Nutrition

Leaves are used as flavoring in curry dishes. Young pods and leaves may be steamed for eating though the first and second waters for boiling should be discarded and the vegetable eaten after thoroughly draining off the third cooking liquid. Seeds have been used for medicine to relieve intestinal worms.


Orwa C, A Mutua, Kindt R , Jamnadass R, S Anthony. 2009 Agroforestree Database:a tree reference and selection guide version 4.0 (http://www.worldagroforestry.org/treedb/AFTPDFS/Senna_siamea.PDF )

Common Names

  • Chinese
    • 鐵刀木
  • Indonesian
    • bujuk
    • dulang
    • johar
  • Malay
    • guah hitam
    • johor
    • juah
    • petai belalang
    • sebusok
  • Thai
    • ขี้เหล็กบ้าน

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