20-Foot Cactus in New Hampshire: Won't Survive Freeze, Must Cut or Heat

40-Year-Old 20-Ft Cactus Too Big for Garage—Winter Options?

Father's 20-ft skinny cactus with basal pups, short spines, brought in every winter. Now too big. Building insulated box with house-heat vent. Asks minimum temperature tolerance.

Neither Cactus Nor Euphorbia Takes Hard Freeze

Greg: most cacti die below 32°F; Euphorbias below 40°F. New Hampshire winters will kill it. Best: cut back and bring in. Heated greenhouse works but expensive. If keeping in box, maintain >40°F at all times.

Practical Advice

• Cut it down—it will regrow from base.
• Or donate to a botanical garden.
• Insulated box + heat vent is risky; power outage = dead plant.