Overwintering Marigolds and Geraniums in a Wisconsin Greenhouse: Annuals Don’t Perennialize

Can You Keep Marigolds Alive Over Winter in a Greenhouse?

A Wisconsin garden crew wants to save marigolds (annuals) in their greenhouse to reuse next year. The answer: theoretically possible but biologically unlikely.

Why Annuals Don’t Overwinter Well

• Marigolds are programmed to grow, flower, set seed, and die in one season.
• No dormancy mechanism exists; they lack the hormones for perennial survival.
• Even with frost protection, light, and warmth, they usually decline and die.

Better Strategies for a Non‑Profit Garden

• Save seeds: Let marigolds go to seed, collect, dry, and sow next spring.
• Geraniums (Pelargonium): Can be overwintered but become woody and tree‑like; hard prune in spring.
• Invest in perennials: Hostas (divide every 2‑3 years), fragrant Hosta plantaginea, bulbs (Scilla, Muscari, crocus – cheap and reliable), vegetables (carrots, broccoli, tomatoes), herbs (basil for fundraisers).
• Cool‑season crops in unheated greenhouse: Broccoli, lettuce, pumpkins.
• Seek donations: Cracked pots, end‑of‑season nursery stock.

Budget Reality

$900 on annuals that die is poor value. Perennials and seed‑grown plants offer long‑term savings and educational opportunities.