What does coolhouse mean?
A coolhouse is a glass structure used in horticulture to shelter plants that need protection from frost without the warmth of a heated greenhouse. Unlike a hothouse, which is kept warm enough for tropical species such as orchids and pineapples, a coolhouse is maintained at modest temperatures—typically just above freezing—making it suitable for temperate plants like camellias, alpines, and certain bulbs that require a cold resting period. Gardeners use coolhouses to overwinter tender perennials, ripen fruit slowly, and start cuttings earlier than outdoor conditions would allow. The word is a straightforward compound of "cool" and "house," and it often appears written as two words, "cool house," especially in traditional British gardening texts. Though less familiar to most readers than "greenhouse," it remains a useful term within the specialised vocabulary of plant cultivation.
nounA glasshouse or conservatory maintained at relatively low temperatures, used for cultivating plants that thrive in cool conditions rather than tropical heat.
- A glasshouse kept at low temperature for growing plants that prefer cool conditions.
"The gardener overwintered her camellias in the coolhouse, where frost was excluded but the air stayed brisk."
"Alpines flourish in the coolhouse, where winter temperatures are held just above freezing."
"He moved his citrus trees into the coolhouse before the first frosts arrived."
Standard pluralisation by adding -s.
"The estate maintained three coolhouses for its collection of temperate ferns."
Not every greenhouse is about heat — the humble coolhouse keeps things chilly on purpose.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coolhouse
The word is an English compound formed from the adjective "cool," of Old English origin (cōl, related to Old Dutch koel), combined with "house," from Old English hūs. It arose within the nineteenth-century tradition of Victorian glasshouse terminology, when gardeners distinguished heated structures—hothouses, stoves, forcing-houses—from unheated or minimally cooled ones.
How coolhouse is actually used
"Coolhouse" is chiefly a horticultural term and appears far less often than "greenhouse"; it frequently occurs as the two-word form "cool house" in gardening literature.
Easily confused with coolhouse
A hothouse is artificially heated to grow tropical plants, whereas a coolhouse is kept only just above freezing to suit hardy and temperate species.