Everyone
who has ever had a decent compost heap cooking away in the winter
frost knows how hot fermenting vegetable matter - with or without
added animal manure - can get. Many gardeners plant cucumbers
or other early spring vegetables into the top of cooling compost
heaps to take advantage of both the heat and the fertility of
the heap.
What
they are doing is using a basic hotbed. All vegetable matter
ferments naturally when piled up, but heaped manure works even
better, and if a heap is large enough, and carefully enough
prepared, then the heat can last for months.
Hotbeds
have been in use from antiquity and were, and continue to be,
used almost exclusively for growing (or forcing) early spring
vegetable and melon crops during the cold weather of mid-to-late
winter when normally such crops would not germinate. By forcing
crops in hotbeds they could then be ready months earlier than
otherwise - a real bonus in Europe when there was a dearth of
green vegetables from February to May.
According
to Aristotle, the ancient Egyptians used dung heaps to hasten
the hatching of eggs, while the Roman emperor Tiberius so loved
his cucumbers that his gardeners grew them for him year round
on wheeled hotbeds (wheeled so they could be moved into shelter
if the weather grew too inclement).
But
it was the Arabs who made the first true hotbeds for early forcing
of vegetables. The Dark Age Arabs who lived on the Iberian Peninsula
(Spain and Portugal), or Moors as they were known, used the
dung of donkeys, horses and occasionally pigeons, to construct
their hotbeds. Their raised hotbeds were fairly small, about
two feet in height and about three square, and were used primarily
to raise seedlings. Once seeds were planted in December, the
Moors covered the top of the hotbed with large vegetable leaves,
such as cabbage or cauliflower leaves, to retain heat and moisture
and watering occasionally as needed. Once the seedlings were
strong, then they would be transplanted out into prepared garden
beds, usually about April.
Evidence
of hotbed use can be found in Europe from the late Dark Ages,
but they appear to have been relatively common from the thirteenth
century. It is impossible to know if hotbeds had been in use
for centuries, but the first recorded use of them occurs
about this time, or if the northern Europeans had only recently
imported the technique (possibly from the Crusades which, while
a military and social disaster, nonetheless resulted in the
Europeans adopting many Arabic techniques, ranging from hotbed
to Arabic numerals). But, from the thirteenth century, soon
hotbeds were steaming ahead across the gardens of Europe.
By
the end of the sixteenth century most gardening treatises mentioned
hot beds and, over the following two centuries, they were put
to good use growing many of the exotic fruits, vegetables and
plants brought home to England and Europe from their increasing
exploration of the new worlds. Universities across Europe developed
botanical gardens, and were often at the forefront of growing
new and exotic species using hotbeds.
It
wasn't just the universities using hotbeds, of course. Many
kitchen gardens used them, particularly within the larger estates,
but anyone who had access to a steaming compost heap had access
to a hotbed.
All they needed do was to add a foot or more of soil, ensure that
the developing seedlings had some protection from the frosts and
other inclement weathers (matting, glass domes, clay pots, blankets,
straw etc.), and they, too, could grow early vegetables. Hotbeds
continued in use for centuries, right through to the nineteenth
century, and although they have gone somewhat out of fashion now
(particularly since the prevalence of greenhouses or hothouses,
they are still a cheap and effective means of growing early seedlings.
To
build a hotbed all you need is a well dug heap of composting manure,
perhaps mushroom compost, and build it up to at least a metre
(about a yard) square by a metre deep. Add to this at least 50
centimeters of good soil, and also a frame for glass or some such
to protect the seedling from frost and cold, and you're set to
go.
You
do not need to use hotbeds exclusively for vegetables or melons.
Anything can grow in them, flowers included, and the top of the
compost heap is a wonderful place to grow nasturtiums.
See
also some eighteenth-century
directions for constructing a hotbed.
Please
also visit Old London Maps
on the web as many of the maps
and views available there have plans and depictions of gardens
from
the medieval period through to the late nineteenth century.
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© Sara Douglass Enterprises Pty Ltd 2006
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