Late last year pineapple fruit were produced in extreme southwest England and with some hyperbole proclaimed to be each worth £10,000. Grown at Cornwall’s Lost Garden of Heligan, suitable tropical conditions were created utilizing 30 tonnes of horse manure, urine and straw.
According to London-based Daily Mail, “Gardeners have grown fruit using the same methods since the 19th century.” Coming from a country to this day redolent in gardeners and gardening, this inaccuracy is surprising.
Two millennia ago, the Roman agriculturalist and writer Agricola explained how to assist cuttings to root by the use of bottom heat. He used a basket of soil encased in a frame filled with fermenting manure.
Pits dug several feet into the ground, also filled with composting manure, appear to have been used in England at least as far back as the 1660s.
Early in the following century, a revolution occurred when it was discovered that crushed oak bark left over from tanning leather released appreciable amounts of heat as it decomposed.
Available in vast quantities, according to the late botanist Anthony Huxley, it was first used to heat glass-covered pits by Henry Telende, gardener to Sir Matthew Decker, who raised England’s first pineapple with its aid in 1720. His brick-lined pit was roughly 5 feet deep, 11 feet long and 7½ feet wide. One February, it was filled with a foot of dung followed by 300 bushels of tan bark. By the end of the month pineapple culture commenced and continued until October.
Both discarded tan bark and horse droppings are in short supply nowadays. But a half-century or so ago it was not unusual for “hot frames” to be created by both amateurs and professionals using essentially the same method, although relying on a couple of feet of manure mixed with straw, covered by a foot or so of soil. Such have been known to reach over 30ºC. Later this was to give way to heating by electric cables. However, present day power costs have tended to limit these.
The opposite though, a “cold frame,” in other words one without any source of artificial heat, may also be encountered from time to time in the gardens of enthusiastic gardeners. Used to raise hardy vegetables over winter, the glass covers retain the sun’s heat during the day, retaining enough at night to protect the crop within when covered with old carpets or similar materials. Indeed, during the day they may become so warm as to require the covering glass frames to be propped up to vent the interiors.
In late winter or early spring, cold frames may also be used for “growing on” seedlings of hardy annual and tender perennial flowers started earlier indoors by enthusiastic amateurs.
Canadian farmer Charlie Farquharson from Parry Sound, Ontario, was well aware of the uses of both hot beds and cold frames when, assisted by his alter ego Don Harron, he recorded in his Allmynack one chilly 20 January: Check wife’s cold frame. Get her to warm her feet before comin’ to bed.
Wes Porter is a horticultural consultant and writer based in Toronto. Wes has over 40 years of experience in both temperate and tropical horticulture from three continents.
