The Nassella tenuissima ‘Pony Tails’ is a genus from the grass family (Poaceae) and is native to the south-western Unites States, northern Mexico and Argentina. The Nassella tenuissima ‘Pony Tails’ is commonly named Mexican feather grass, Texas needle grass or spear grass and is also know under the synonyms Stipa tenuifolia and Stipa tenuissima.
The Mexican feather grass forms a compact, upright tuft of attractive threadlike, green leaves. The airy, feather-like flower heads appear in May atop of the leaves. They are green at first, but they turn silvery white in summer and then to brown.
The Nassella tenuissima ‘Pony Tails’ easily spreads through seed. Young, new seedlings are easy to recognize and remove, but they appear everywhere. The Nassella tenuissima ‘Pony Tails’ produces many seeds and they spread through the wind, water, cars and animal droppings. This is why it is placed on the list of invasive plants in California and Australia.
The leaves normally stay upright, but when this ornamental grass has reached its full height in summer the leaves may fall flat to the ground after heavy rain. The stems cannot carry the weight of the wet flower plumes. The grass will fall on top of the surrounding plants and smother them. That is the reason why I do not have any photographs of the white flower plumes, because the rain had flattened the grass by then.
You can prevent the flattening and spreading of the Nassella tenuissima ‘Pony Tails’ by cutting it just below the flower plumes at the end of June/beginning of July. New leaves and flowers will grow and it will rebloom at the end of the summer. You can cut the grass just under the flowers again in autumn to prevent it from spreading. Because the flower plumes are so ornamental it may be a pity to cut them off. After the winter you can cut the tufts to about 20 cm from the ground or pull out the dead leaves by hand.
The Nassella tenuissima ‘Pony Tails’ looks beautiful in a group or as a single accent. An alternative in California could be Pennisetum alopecuroides or Bouteloua gracilis.
The Mexican feather grass prefers a sunny and well-drained position. It tolerates drought, heat and salt. This ornamental grass is very suitable for rock gardens. In mild winter climates the Nassella tenuissima ‘Pony Tails’ is evergreen, but in colder winter climates the leaves will die to the ground. That is why I have indicated that the grass will newly emerge every year at the specifications.
Attracts bees: no
Characteristic: newly emerging every year
Deer resistant: yes
Exposure: sun/ part shade
Flower color: white
Flowering time: May – August
Foliage color: green
Fragrant flower: no
Hardiness: -15 ºC (5 ºF)
Height: 24 inches (60 cm)
Soil: normal/ dry