Cold hardiness & minimum temperature

Is Green Comet Milkweed (Asclepias viridiflora)cold hardy? Hardiness zone & min temp

Also called Green Comet Milkweed, Short Green Milkweed, Green-Flowered Milkweed, Wand Milkweed.

More about green comet milkweed

About Green Comet Milkweed

Asclepias viridiflora · also called Green Comet Milkweed, Short Green Milkweed · flowering

Green comet milkweed is a compact native perennial found across dry prairies, open woodlands, savannah edges, and limestone glades from Manitoba to Florida. Its nodding clusters of pale green flowers appear in upper leaf axils from June to August, and it tolerates both dry and moderately shaded conditions unusual for milkweeds. The most important care fact is that it prefers dry, lean soil and is very intolerant of standing water or heavy clay — excellent drainage is non-negotiable. All Asclepias species contain cardiac glycosides and are toxic to cats and dogs.

Cold limit: USDA 3-9 · RHS H7 (-40°C to 38°C)

What green comet milkweed's hardiness rating actually means

Yes — green comet milkweed is genuinely cold hardy. Rated RHS H7 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 3-9 — 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 below about −20 °C. Green Comet Milkweed is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for green comet milkweed as it gets too cold:

It tolerates winter lows to about −20 °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 green comet milkweed go outside or overwinter — and where?

Plant it out within USDA 3-9 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 green comet milkweed can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Green Comet Milkweed hardiness — frequently asked questions

Is green comet milkweed cold hardy?

Yes — green comet milkweed is genuinely cold hardy. Rated RHS H7 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Green Comet Milkweed is hardy across USDA 3-9; 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 green comet milkweed can survive?

Minimum survivable temperature is roughly below about −20 °C. Green Comet Milkweed is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is green comet milkweed?

Green Comet Milkweed is rated USDA 3-9 and RHS H7 — Hardy in the severest European continental winters.

Can green comet milkweed survive winter outside?

Plant it out within USDA 3-9 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 green comet milkweed below its minimum temperature?

It tolerates winter lows to about −20 °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.