Cold hardiness & minimum temperature

Is Lawson Cypress (Chamaecyparis lawsoniana)cold hardy? Hardiness zone & min temp

Also called Lawson Cypress, Port Orford Cedar, Oregon Cedar.

More about lawson cypress

About Lawson Cypress

Chamaecyparis lawsoniana · also called Lawson Cypress, Port Orford Cedar · flowering

Lawson Cypress is a tall, elegant conifer native to a narrow coastal strip of Oregon and California, widely planted worldwide for its feathery, pendulous sprays of blue-green to grey foliage. Hundreds of cultivars range from dwarf globes to towering specimens. Hardy and adaptable in cool, moist climates, but highly susceptible to Phytophthora lateralis root rot.

Cold limit: USDA 5-8 · RHS H5 (-15°C to 25°C)

Watch for — Juniper scale (Carulaspis juniperi): White, encrusting scale insects on foliage cause yellowing and dieback. Treat with horticultural oil in late winter before hatch, or systemic insecticide in spring. Improve air circulation by thinning dense plantings.

What lawson cypress's hardiness rating actually means

Yes — lawson cypress is genuinely cold hardy. Rated RHS H5 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 5-8 — 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 −15 to −10 °C. Lawson Cypress is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for lawson cypress as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 lawson cypress go outside or overwinter — and where?

Plant it out within USDA 5-8 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 lawson cypress can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Lawson Cypress hardiness — frequently asked questions

Is lawson cypress cold hardy?

Yes — lawson cypress is genuinely cold hardy. Rated RHS H5 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Lawson Cypress is hardy across USDA 5-8; 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 lawson cypress can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Lawson Cypress is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is lawson cypress?

Lawson Cypress is rated USDA 5-8 and RHS H5 — Hardy in most of the UK and in cold winters.

Can lawson cypress survive winter outside?

Plant it out within USDA 5-8 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.

What happens to lawson cypress below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.