Scientific name: Leucaena Leucocephala
Common names: Tan-tan, River Tamarind, White Tamarind, Lead Tree, White Lead tree, Jumbay, Pearl Wattle, Ipil-Ipil, and White Popinac.
The shrub we know on St Croix as Tan-Tan, properly named Leucaena Leucocephala, in the Fabaceae family, was introduced to St Croix in the 1950s. It is a fast-growing, evergreen tree that is native to southern Mexico and northern Central America. In Central America, it can grow up to 20 meters tall, but that height would be unusual on St Croix where the height is generally less than 20 feet.
It is often confused with Lysiloma latisiliquum or wild tamarind, which is also in the Fabaceae family.
Most people on St Croix consider the Tan-Tan to be an invasive species, and certainly it has the potential to outcompete native species if not controlled.
It is called a “miracle tree” because it provides a variety of benefits.
Introduced to combat soil erosion, improve soil fertility, and provide a source of food for livestock, it is drought tolerant, fast growing, and has a deep root system that prevents erosion and improves soil structure It can tolerate a wide variety of soil types including poor fertility. It was perfect for St Croix because of the significant degradation of the soil due to over 200 years of the sugar industry. It has the unique ability to fix atmospheric nitrogen1, improving and restoring soil fertility without the need for fertilizers.
The foliage is highly nutritious and used for animal feed (and as human food in Central America, Indonesia, and Thailand). It is notable for its fern like leaves that fold up in extreme dry weather, spherical flowers and long seed pods that start out green but turn dark brown and split open to release the seeds.
Anything of great benefit has to have a detrimental offset, and this is true for the Tan-Tan. The leaves and seeds contain mimosine, an amino acid that can be toxic if ingested in high concentrations. These toxic effects include:
- Alopecia (hair/fur loss)
- Poor body condition
- Infertility
- Low birth weight
- Thyroid gland dysfunction
- Organ toxicity
- The ability to fix atmospheric nitrogen refers to the process of converting atmospheric nitrogen gas (N2) into a usable form, such as ammonia (NH3) or nitrate (NO3-), that can be utilized by plants and other organisms. Nitrogen fixation is an essential biological process that is carried out by certain bacteria, archaea, and some plants. These nitrogen-fixing organisms possess enzymes called nitrogenase that can break the strong triple bond between nitrogen atoms in the N2 molecule, allowing the nitrogen to be incorporated into organic compounds. This ability is crucial for the overall nitrogen cycle and plays a vital role in maintaining the availability of nitrogen for various biological processes ↩︎