It can remain useful for a long season, but winter growth depends on your local climate, light levels, and how cold the greenhouse becomes. Mint may slow dramatically or die back in colder conditions, then restart as light and warmth return. Protect containers from repeated hard freezing if you want to keep roots viable, and reduce watering while growth is slow.

A 12- to 16-inch container is a strong practical starting point for one plant. It provides enough root room to maintain moisture more evenly than a tiny pot while keeping the plant visibly contained. Choose a container with drainage holes, and repot or divide when the root mass becomes crowded and growth loses vigor.

You can, but it is rarely the best long-term greenhouse strategy. More vigorous varieties can overtake slower ones, labels become meaningless, and separating roots later is frustrating. For a collection that stays intentional, assign every aroma family its own pot and arrange the pots together as a mint bar.

Legginess commonly reflects insufficient light, excessive warmth, overcrowding, or a plant that has not been pinched regularly. Increase usable light, improve ventilation, trim above nodes, and avoid pushing the plant with heavy fertilizer. Rotate the container if growth leans strongly toward one glazing wall.

Usually no. Mint benefits more from steady root-zone moisture and adequate air movement than from repeatedly wet leaves. Misting can leave foliage damp without correcting a dry root ball, and a crowded, humid canopy can encourage disease. Water the potting mix directly and ventilate the greenhouse.

Place each pot where runners cannot touch soil in adjacent containers, inspect the rim and drainage holes regularly, and lift the pot occasionally to check below it. Never discard divisions, pulled runners, or old potting mix casually into a greenhouse bed or compost pile unless you are certain the material is fully dead.