A greenhouse is a structure clad in glass or transparent plastic in which plants are grown under shelter — the smaller-scale cousin of the commercial glasshouse. By trapping solar warmth and buffering wind, rain, and frost, it extends the growing season, protects tender crops, and lets gardeners raise seedlings, tomatoes, peppers, and exotics that would fail outdoors in cool climates. Ventilation, shading, and watering must be managed: an unventilated greenhouse overheats rapidly, and still, humid air invites fungal disease. From Victorian ferneries to modern allotment polytunnels, the greenhouse embodies the gardener’s desire to cheat the climate — a simple technology that transformed what temperate gardeners and smallholders can grow and eat.