Nitraria tangutorum Seeds | Tangut Nitraria
LATIN NAME: Nitraria tangutorum
COMMON NAME: Tangut Nitraria
Plant Profile
Tangut nitraria is a low, sprawling shrub, usually half a metre to a metre and a half tall, with whitish, zigzag branches that end in a spine and carry small, fleshy, grey-green leaves in clusters. The habit is dense and mounded, and the plant has a way of growing upward through any sand that accumulates around it, which is the key to its whole ecology. The flowers are small, white to greenish, five-petalled and inconspicuous, appearing in late spring, and they are followed by round drupes that turn scarlet and then dark purple-red as they ripen in late summer.
The fruit is edible and surprisingly good, sweetish and slightly salty, with a thin skin and a single stone, and it is collected across the deserts of northern China as a seasonal treat and pressed for juice. The species is native to the dry lands of the Alashan plateau, Ningxia, Gansu, Qinghai and the margins of the Qaidam and Tarim basins, where it grows on sand dunes, gravel plains and saline flats, usually where the water table is within a few metres of the surface. It is a phreatophyte, drawing on groundwater with a deep root system while the shallow roots spread widely to catch whatever rain falls. Where it grows, it collects windblown sand into mounds that can be two or three metres high and many metres across.
Science & Biotechnology
Those mounds, called nebkhas, are the reason the species appears so often in geomorphology as well as in botany. The shrub slows the wind at its base, sand drops out of the airstream, and the plant grows up through the accumulating pile, so that the mound is a record of the interaction between vegetation and wind. Studies in the Alashan have measured accretion rates, the grain size of the trapped sand, and the way the mounds alter the local wind field and create islands of fertility in an otherwise bare plain. The organic matter and moisture held in a nebkha support a different community of plants and soil organisms from the surrounding gravel.
The species is also a model for drought and salt tolerance. Its roots reach the capillary fringe, its stomata close early in the day, and its tissues accumulate compatible solutes that keep cell turgor as the soil dries. Work on its seed biology has shown that the hard, woody endocarp imposes dormancy that is broken by a warm, moist period followed by cold, which synchronises germination with the spring melt. Clonal growth from root suckers lets a single plant spread into a patch several metres across, and the fruit is dispersed by foxes, badgers and birds that eat the drupes and pass the stones intact. Genetic studies of populations across the desert show moderate differentiation, consistent with limited seed movement between oases.
Uses & Benefits
Tangut nitraria is one of the cornerstones of sand fixation in northern China. It is planted in shelterbelts around oases, along railways and roads crossing the desert, and on the margins of the Tengger and Badain Jaran, usually together with sea buckthorn, tamarisk and Caragana. Its value lies in the combination of a deep root, a dense low canopy and the ability to bury itself in drifting sand, which no grass or annual can match. The fruit is harvested for juice, jam and a traditional wine, and the seed oil has been examined for its fatty acid profile.
In Chinese medicine the fruit is used as a tonic for the kidney and for general debility, and the bark and leaves have local uses that are less well documented. The plant has no ornamental tradition and is unlikely ever to have one, since its habit is untidy and its flowers are tiny, but it is a genuine curiosity for a dry garden or a sand garden where its sprawling, spiny form and scarlet fruit can be seen close to. It is also extremely useful on a bank of pure sand, where it will hold the surface and let other plants establish behind it.
Growing from Seed
The stone is hard and the seed inside it is dormant. Soak the fruits, rub away the flesh, and then either crack the stones carefully or give them a warm, moist period of six to eight weeks at twenty-five degrees followed by four weeks at four degrees. A soak in gibberellic acid before sowing improves the percentage that comes up. Sow into a sandy mix, cover lightly, and keep warm and only moderately moist, since the seed rots in wet compost. Germination is slow and uneven, spread over two to three months.
Prick the seedlings out into deep pots, because the taproot goes down fast and the plant resents confinement. Grow them on in full sun and a gritty, free-draining mix, with no rich feeding, which produces soft growth that dies in the first dry spell. Plant out into pure sand or gravel in autumn, water twice, and then leave the plant alone. It will send roots down to find its own water. Do not transplant once established, and do not plant in a border or anywhere that receives irrigation, which kills it faster than drought.
Our Take
A desert plant that earns its place by holding ground rather than by looking pretty. For a sand bank or a dry, exposed slope it is close to ideal, and the fruit is a genuine bonus.
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