Greenhouse growing places plants under glass or plastic film, so they receive sunlight but are protected from rain, wind and some pests. Structures range from simple unheated hoop houses (polytunnels) to fully climate-controlled glasshouses with heating, cooling, dehumidification, blackout curtains and supplemental lamps ("mixed-light").
In practice
Glazing and frames block some light; a typical greenhouse transmits roughly 60-80% of outdoor light depending on the covering and its agebeing reviewed. The structure extends the season at both ends and keeps late-flower buds dry, the biggest advantage over open outdoor growing. Blackout systems allow light deprivation for several harvests per year, and supplemental lighting raises DLI in winter.
Greenhouses heat up fast on sunny days; ventilation and shading are essential, and humidity spikes at dawn and dusk are a common mould trigger.
Don't confuse with
- Light dep: a technique often used in greenhouses, not the structure itself.
- Indoor: no sunlight at all.
