Stipa tenuissima (Mexican Feather Grass)

Stipa tenuissima, commonly known as Mexican Feather Grass or Ponytails, is a perennial evergreen grass with stiff, threadlike green leaves that form a neat, dense, upright to slightly arching clump resembling a fountain.

During spring and summer, silky, feathery spikes of silver-green flowers emerge slightly above the foliage, turning golden in autumn and winter.

It is a hardy and drought-tolerant plant native to Texas, Mexico, and Argentina.

It can be dangerously invasive, especially in Australia.

Stipa tenuissima plant (Mexican Feather grass)

Quick Overview

TYPE

Type herbaceous

HEIGHT & WIDTH

stipa tenuissima height and width

BLOOM TIME

stipa tenuissima bloom time

SUNLIGHT

full sun

HARDINESS

hardiness (-12ºC / 10º F)

DROUGHT TOLERANCE

drought tolerance aprox 5 months

ORIGIN

Mexican Feather Grass Scientific name

  • Botanical name:  Stipa tenuissima (STY-puh ten-yoo-ISS-ih-muh)
  • Family: Poaceae (po-AY-see-eye)
  • Common name: Mexican Feather grass, Pony tails, Angel hair
  • Synonyms: Nassella tenuissima (most recent classification)
NameMeaning
StipaLatin word meaning stalk or straw.
tenuissimaDerived from latin word “tenui” meaning thin. The suffix “issima” indicates “very”. Thus the complete word means “very thin”. Referring to its thin thread-like leaves.

How to identify Stipa tenuissima

Stipa tenuissima plant (Mexican Feather grass)

Plant

Stipa tenuissima is a small perennial evergreen grass that forms a dense, vertical clump of upright threadlike green leaves. The taller leaves tend to droop at the tip and the leaves at the edge are shorter and bend away from the plant. The overall effect is like a fountain.

During the spring and summer months, numerous soft, silky silver-green flower spikes emerge slightly above the foliage. During the autumn these flower spikes turn to golden brown.

The average height is 40 to 50 cm  (1.3 to 1.6 ft),  70cm (2.3 ft) with flower. The width is 50 cm (1.6 ft).

Stipa tenuissima stem (Mexican Feather grass)

Stem

Stipa tenuissima has delicate, slender flower stems. They are light green and carry feathery flower spikes

The stem is slightly taller than the foliage and has a sheath that looks like a leaf at the bottom of the flowers.

The height of the flower stem is, on average, 70 cm (2.3 ft) or more, but the longer stems bend over.

Stipa tenuissima leaf (Mexican Feather grass)

Leaf

The leaves are very thin, stiff, and green

The leaf shape is linear and it is tightly rolled up and overlapping at the edges.

The length is up to 60 cm ( 2 ft) and width is around 0.25–0.5 mm.

At the base of the leaf blade, there is a ligule (a small, thin structure that looks like tissue paper), which is papery and smooth and around 0.5–2.5 mm long.

Stipa tenuissima flower (Mexican Feather grass)

Flower

The inflorescence is a thin feathery panicle 15 to 25 cm (6 to 10 inches) long. The branches are tightly packed together. Each branch has numerous spikelets arranged in a spiral pattern on one side.

The spikelets are silver-green and have a long silky awn (which looks like long hair) around 4.5 to 9 cm (2 to 3.5 inches) long.

These long awns give the flower spike its soft feathery look.

The flowers emerge from late spring to early summer with a silvery green colour and turn to a golden hue in autumn. They last until the end of winter, giving the garden year-round interest.


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Stipa tenuissima Habitat

Stipa tenuissima is native to Texas, Mexico, and Argentina, hence the common names Mexican feather grass or Argentine needle grass.

It grows naturally in open woodlands, stony slopes and grasslands.

Stipa tenuissima Usage

Ornamental

Mexican feather grass, with its fountain-like appearance and silky, feathery flower spikes, forms a translucent curtain that sways with the slightest breeze. Its long-lasting flower heads and evergreen foliage add interest all year round.

It is also a very tough plant that requires little attention, making it a great option for a low-maintenance garden.

It can be used in the landscape in the following ways:

  1. Focal point: Its fine texture and graceful fountain-like form make it an excellent focal point in garden beds and borders. Its soft feathery appearance draws the eye and adds visual interest to the landscape. When illuminated by early morning or late afternoon sunlight, it creates a dramatic effect, especially when it is backlit.
  2. Texture and movement: Stipa tenuissima brings texture and movement to garden designs. The soft, feathery flower spikes offer a gentle contrast with surrounding plants and hard surfaces while also introducing movement when swaying gently in the breeze.
  3. Naturalistic plantings: Stipa tenuissima is often used in naturalistic or prairie-style plantings to create a sense of movement and wildness.
  4. Contemporary gardens: Its upright growth habit makes it well-suited for linear plantings in contemporary gardens. It can be used to create linear borders, edgings, or mass plantings along pathways, walls, or fences, adding a sense of rhythm and movement to the landscape.
  5. Rock Gardens: Incorporate it into rock gardens to soften the hard edges of rocks and boulders. Its airy texture and graceful form complement the rugged beauty of a rock garden.
  6. Container Plantings: Plant it in containers or pots to add height, texture, and visual interest to patio or balcony gardens. It can be used as a focal point or as a filler plant in mixed container arrangements.

Biodiversity

Stipa tenuissima provides habitat and food sources for various wildlife species, including birds and insects, making it beneficial for promoting biodiversity in your garden.

Dried Flower Arrangements

The flower heads with long awns add a unique texture and natural elegance to dried floral displays. When harvested at the height of bloom and hung upside down in a cool place to dry, the flower spikes retain their shape and colour when dried. 

Erosion Control

The dense clumps of Stipa tenuissima can help stabilize soil on slopes, making it useful for erosion control in landscaping.

Is Mexican Feather grass invasive?

Stipa tenuissima can become invasive in certain environments. It is especially invasive in Australia and is considered a major threat.

Before planting it in your garden you should check if it is invasive in your area.

How to care for Stipa tenuissima

Cold exposure

Mexican Feather Grass can tolerate frost and cold weather down to  -12ºC (10º F). But only if the soil is well drained. Cold, soggy soil can be fatal to it. 

While the plant is not yet established, you may want to add a thick layer of mulch around the plant’s base to protect the roots from cold temperatures. It´s preferable to use gravel mulch because organic mulch will stay humid and can cause the plant to rot.

Sun exposure

Mexican feather grass thrives best in full sun but it can tolerate partial shade.

Soil

Mexican feather grass thrives in poor, well-drained soils, particularly those with a gritty, rocky texture. It’s best to avoid planting it in damp locations, as it is not tolerant of soggy soil, which can increase the risk of root rot.

If your area tends to become waterlogged, you may need to keep the entire root ball above ground level and fill in with a raised mound of sandy soil, sloping gradually away from the plant’s base.

It can tolerate most types of soil PH, from mildly acidic to neutral to mildly alkaline.

Avoid fertilizing the soil to prevent it from flopping over and to ensure that it remains robust and better equipped to handle extreme temperatures.

Watering

Mexican feather grass is very drought tolerant and can go for months without water once it is established (about 5 months of drought if the temperature is not too hot). 

During its first year after planting, it’s essential to water the young plant regularly. Depending on the soil and the temperatures, you may need to water it once a week, every two weeks or every three weeks.

When you water the plant, make sure to give it plenty of water, allowing the soil to get a good soak. This way, the water can sink deep into the soil keeping it moist for longer periods.

To preserve the soil´s moisture, you should add mulch around the root area of the plant. The mulch should preferably be gravel because organic mulch can lead to leaf rot.

Pruning

Evergreen grasses such as Stipa tenuissima do not need to be cut back. 

Instead, you should remove the dried flower heads by the end of winter, which can be pulled off easily. 

After that, comb through the leaves with your fingers to remove the old leaves. This is important because if you leave the old leaves, the plant will be stunted because the new leaves cannot easily grow through them. So, try to clean out as much of the dead material as possible.

There are two ways to remove the old leaves:

  • With your hands – Gently remove the dead leaves, leaving the crown with only the fresh green leaves. Wear gloves for this task because the sharp grass blades can cut your fingers. 
  • With a rake – Alternatively, you can also rake it, which is a faster way of doing this. However, it may damage the new leaves, and you will not get such a nice result. It all depends on how much time you have to do this task. 

When to plant Stipa tenuissma

The best season to plant is typically spring or autumn, but it depends on your climate. You should avoid planting during periods of extreme temperatures.

If you have mild weather where you live, it’s best to plant in the autumn to give it time to develop the roots during the cooler months before the arrival of the hot summer. In case of very cold winters, it’s better to wait until spring when the risk of frost has passed and the soil is warmer. That way, the plant can have a better chance to grow well and be healthy.

How to propagate Stipa tenuissima

Stipa tenuissima can be propagated by seed or by division.

Division: Mid-Spring to early summer

  1. Dig up the mother plant clump.
  2. Shake off the excess soil to make it easier to divide.
  3. Divide the clump into good-sized sections. Depending on the size of the clump, use a sharp knife, a spade, or even a saw.
  4. Replant the divisions into the garden 

Seed: Early spring to early summer

  1. Sow the seeds in a well-draining medium. Lightly press the seeds into the soil, just covering them with a thin layer, as the seeds need light to germinate.
  2. Maintain consistent moisture but not soggy (cover with a plastic lid or bag) and provide indirect light. 
  3. For best germination, maintain a temperature around 15 to 18ºC (60 to 65ºF). Germination should take 2 to 4 weeks, but it can also be erratic and take several months.
  4. Water from the base of the container (don´t water overhead)
  5. Once the seedlings have grown a few sets of true leaves, transplant them into individual containers and grow in cold frame during the first winter, or harden them to outdoor conditions and then plant into their permanent positions after the last expected frosts. 

Sources of information used for this article

Sources

Article from Kew

Article from Jardin-sec

Article NSW Weedwise

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