Cold hardiness & minimum temperature

Is Gyoku-ryu Mondo Grass (Ophiopogon japonicus 'Gyoku-ryu')cold hardy? Hardiness zone & min temp

Also called gyoku-ryu mondo grass, miniature mondo grass.

More about gyoku-ryu mondo grass

About Gyoku-ryu Mondo Grass

Ophiopogon japonicus 'Gyoku-ryu' · also called gyoku-ryu mondo grass, miniature mondo grass · houseplant

Ophiopogon japonicus 'Gyoku-ryu' is a dwarf, ultra-compact mondo grass forming tight cushions of very short dark-green foliage, typically only a few centimetres tall. Extremely slow-growing, it is prized for fairy gardens, bonsai underplanting, troughs and stepping-stone joints. It shares mondo grass's shade tolerance and toughness while staying tiny and dense.

Cold limit: USDA 7-11 (outdoor in mild zones; houseplant elsewhere) · RHS H4 (15 to 27°C)

What gyoku-ryu mondo grass's hardiness rating actually means

Yes — gyoku-ryu mondo grass is genuinely cold hardy. Rated RHS H4 and USDA 7-11 (outdoor in mild zones; houseplant elsewhere), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 7-11 (outdoor in mild zones; houseplant elsewhere) — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

Minimum survivable temperature is roughly about −10 to −5 °C. Gyoku-ryu Mondo Grass is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for gyoku-ryu mondo grass as it gets too cold:

It tolerates winter lows to about −10 to −5 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can gyoku-ryu mondo grass go outside or overwinter — and where?

Plant it out within USDA 7-11 (outdoor in mild zones; houseplant elsewhere) and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when gyoku-ryu mondo grass can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Frost protection for borderline gyoku-ryu mondo grass

Gyoku-ryu Mondo Grass is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

At the cold edge of its range, mulch the root zone in late autumn to buffer the deepest freezes.
Protect container specimens — pots freeze through far faster than open ground, costing roughly a zone of hardiness.
Shelter new growth from late spring frosts with fleece if a hard night is forecast.

Gyoku-ryu Mondo Grass hardiness — frequently asked questions

Is gyoku-ryu mondo grass cold hardy?

Yes — gyoku-ryu mondo grass is genuinely cold hardy. Rated RHS H4 and USDA 7-11 (outdoor in mild zones; houseplant elsewhere), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Gyoku-ryu Mondo Grass is hardy across USDA 7-11 (outdoor in mild zones; houseplant elsewhere); it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature gyoku-ryu mondo grass can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Gyoku-ryu Mondo Grass is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is gyoku-ryu mondo grass?

Gyoku-ryu Mondo Grass is rated USDA 7-11 (outdoor in mild zones; houseplant elsewhere) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can gyoku-ryu mondo grass survive winter outside?

Plant it out within USDA 7-11 (outdoor in mild zones; houseplant elsewhere) and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

How do I protect gyoku-ryu mondo grass from frost?

At the cold edge of its range, mulch the root zone in late autumn to buffer the deepest freezes. Protect container specimens — pots freeze through far faster than open ground, costing roughly a zone of hardiness. Shelter new growth from late spring frosts with fleece if a hard night is forecast.