Repotting guide

When & how to repot Pony Tails Grass (Stipa tenuissima)

Also called ponytails grass, fine-leaved tussock grass.

More about pony tails grass

About Pony Tails Grass

Stipa tenuissima · also called ponytails grass, fine-leaved tussock grass · flowering

Stipa tenuissima (now Nassella tenuissima) is a soft, fine-textured ornamental grass forming feathery tussocks that ripple in the slightest breeze. Bright green spring foliage matures to buff with silky flower plumes. It thrives in full sun and sharp drainage, is very drought-tolerant, and self-seeds freely, which can become invasive in mild climates.

Mature size: Typically 40-60 cm tall and wide, the flower plumes adding a little height above the foliage.

Watch for — Crown rot on wet soil: Winter wet is the main killer. Plant in sharp drainage and avoid heavy clay or low spots that hold water.

How to tell pony tails grass needs repotting

Repotting on a calendar is less reliable than reading the plant. For pony tails grass, watch for these signs:

Roots growing out of the drainage holes, or the rootball lifting the plant proud of the rim.
Soil that has shrunk away from the pot sides and no longer holds water.
The pot is unstable because the plant has grown top-heavy.
Old, compacted, broken-down mix that stays wet too long — for a succulent that is a rot risk, so refresh it even if the pot size is fine.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot pony tails grass

Every 2–3 years, into bone-dry mix. Pony Tails Grass's growth habit — compact, clump-forming deciduous-to-semi-evergreen grass. forms dense, fountain-like tussocks of thread-fine leaves topped in summer by silky, hair-like flower plumes that bleach to pale straw. — sets the pace. Stipa tenuissima (now Nassella tenuissima) is a soft, fine-textured ornamental grass forming feathery tussocks that ripple in the slightest breeze. Bright green spring foliage matures to buff with silky flower plumes. It thrives in full sun and sharp drainage, is very drought-tolerant, and self-seeds freely, which can become invasive in mild climates.

What size pot to step pony tails grass up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Pony Tails Grass stores water and rots in a large pot of slow-drying soil. A tight terracotta pot that dries fast is far safer than a generous plastic one. Never up-pot a succulent by several sizes.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot pony tails grass

Spring or summer, while pony tails grass is in active growth and warm, is best — roots recover fastest then, and the plant is not sitting in cool damp soil. Avoid repotting a succulent in winter dormancy.

Step-by-step: repotting pony tails grass

Repot dry. Do not water pony tails grass for several days first. Working with dry roots and dry mix dramatically lowers the rot risk for a succulent.
Pick a snug, fast-draining pot. Choose terracotta one size up at most, with a drainage hole. Have gritty light, gritty, free-draining loam, sand or chalk of low fertility ready.
Tip it out and clean the roots. Slide the plant out, crumble off the old soil, and trim any black, mushy or dead roots with clean snips.
Pot into dry mix. Set pony tails grass at its original depth in dry gritty mix, firming gently. Do not bury the stem deeper than it was.
Wait a week before watering. Leave it completely dry and out of harsh sun for about 7 days so any damaged roots callus. Only then water lightly.

Aftercare

Keep pony tails grass completely dry and out of fierce sun for about a week so any nicked roots callus before they meet moisture; watering a freshly repotted succulent is the classic way to rot it. Then resume the normal lean, dry rhythm. Do not fertilise for about 3 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for pony tails grass

Pony Tails Grass wants light, gritty, free-draining loam, sand or chalk of low fertility. Excellent drainage is critical. It excels on poor, dry, gravelly soils; rich or wet ground promotes soft growth, rot and short-lived plants. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting pony tails grass — frequently asked questions

How often should you repot pony tails grass?

Every 2–3 years, into bone-dry mix for pony tails grass. Repot pony tails grass every 2–3 years into a snug pot of light, gritty, free-draining loam, sand or chalk of low fertility, ideally in spring or summer. Let it sit in dry soil and do not water for about a week afterwards so any nicked roots can callus. Over-potting and watering straight away is what rots succulents.

What size pot does pony tails grass need?

When is the best time of year to repot pony tails grass?

Should you water pony tails grass after repotting?

No — not straight away. Repot pony tails grass into dry mix and wait about a week before the first watering so any damaged roots callus over. Watering a freshly repotted succulent is the single most common way to rot one.

Should you fertilise pony tails grass after repotting?

Not immediately. Wait about 3 weeks after repotting pony tails grass. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.