Cold hardiness & minimum temperature

Is Mayhaw (Crataegus aestivalis)cold hardy? Hardiness zone & min temp

Also called mayhaw, summer haw.

More about mayhaw

About Mayhaw

Crataegus aestivalis · also called mayhaw, summer haw · edible

Mayhaw is a small Southern hawthorn prized for the tart red-to-yellow fruit that ripens in May, famously made into mayhaw jelly. Native to wet bottomlands and swamp margins of the US Southeast, it is unusually tolerant of seasonally flooded ground for a tree, while still fruiting well in ordinary moist garden soil.

Cold limit: USDA 6-9 · RHS H5 (-23 to 38°C)

Watch for — Poor fruit set: Light cropping often traces to too much shade, late frost on blooms, or low pollinator activity; full sun and an open site improve yield.

What mayhaw's hardiness rating actually means

Yes — mayhaw is genuinely cold hardy. Rated RHS H5 and USDA 6-9, 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 6-9 — 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. Mayhaw is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for mayhaw 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 mayhaw go outside or overwinter — and where?

Plant it out within USDA 6-9 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 mayhaw can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Mayhaw hardiness — frequently asked questions

Is mayhaw cold hardy?

Yes — mayhaw is genuinely cold hardy. Rated RHS H5 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Mayhaw is hardy across USDA 6-9; 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 mayhaw can survive?

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

What hardiness zone is mayhaw?

Mayhaw is rated USDA 6-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can mayhaw survive winter outside?

Plant it out within USDA 6-9 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 mayhaw 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.