Hot beds are nothing new: they were used by the Victorians and by the Romans. By reviving and modernising this ancient vegetable-growing method, Jack First produces healthy plants that crop at least two months earlier than conventionally grown vegetables, even in his native Yorkshire. This practical, illustrated guide has everything you need to understand how to use this highly productive, low-cost, year-round, eco-friendly gardening technique. Straightforward explanations and diagrams show how the natural process of decay can be harnessed to enable out-of-season growing without using energy from fossil fuels or elaborate equipment.
HOT BEDS
“ Jack is a fountain of knowledge and the expert on hot beds. When I visited his allotment and saw how advanced and healthy his crops were, it proved to me that these ancient old systems still work a treat and are just as relevant now – if not more so – than they ever were.” Joe Swift, garden designer and TV presenter
With just stable manure (or alternatives), a simple frame and a small space, you can be harvesting salads in March and potatoes in early April.
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Distributed in the USA by Chelsea Green
JAC K F I R S T
Jack First is an experienced horticulturalist who has pioneered, developed and fully tested the hot bed methods described in this book. He works with volunteers on a large plot in Keighley and is the sole supplier to his local food cooperative of out-of-season greens, new potatoes and salads.
JAC K F I R S T
How to grow early crops using an age-old technique
HOT BEDS
Chapter 1
Hot beds are nothing new The problem of growing crops early in the British Isles and other temperate zones was pondered and answered at least two thousand years ago. If you have ever looked at a stack of stable manure on a cold day, you will have noticed that steam is visible. Clearly there must be a heat source, and this is a fact that was
not missed by the Romans. The gardeners of Tiberius (42bc–ad37) had a problem, as their emperor demanded salads out of season. They built beds of stable manure and placed frames upon them. Soil was put inside, and the frames covered with thin sheets of ‘talc’ (translucent sheets that let light through). The manure warmed not only the soil but also the air in which the crops grew.
A hot bed is a warmed, protected environment, created by heat generated from decomposing organic matter, used for producing early crops. In fact, hot beds of some form were probably in use before the Roman era, as animals were domesticated thousands of years prior to this period. Humans lived in close proximity to their animals, often directly above them in the same building, where they benefitted from the warmth of the stock. Seeds in horse feed readily pass into the dung, and hay containing seeds is often mixed with the litter of other penned animals. This litter, probably also containing food scraps thrown down from the household above, would have been taken from a pen or stable and stacked outside, much in the same way as is practised today. Our ancestors would have beheld the bewildering sight of germinated seeds growing on the fermenting stack when all around was covered in snow or ice. Perhaps, in the pre-historical era, this revelation led to the first hot beds. In those harsh times the ability to grow early crops would have considerably improved survival rates. Down the years many nations have understood and adopted this principle. Up until the First World War Parisian market gardeners were masters of this art, supplying not only their home market with early crops but that of Covent Garden too. One of the French methods,
CHAPTER 1
Hot beds are nothing new 11
or more. It gradually cools over a period of several weeks or even a few months. The higher the stack, the longer the heat will last.
Hot bed basics
We also know that these microorganisms require air and moisture, and that a shortage of either will reduce or even prevent decomposition. Too much water will not only cool the manure but also drive out the air that these microbes need. Given the right conditions, a hot bed will produce heat over a long period. More importantly, although the temperature slowly declines, heat is released both day and night. As the microbes’ food supply is exhausted, the heat gradually fades. At this point earthworms enter the manure and not only aerate it but also increase its fertility by way of their casts. Armed with this information, our aims when making use of hot beds are as follows: l
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To manage the manure in such a way as to create ‘bottom heat’ in the bed. To manage that heat over as long a period as possible. To use it when it is most needed, and that is from January to April, while light levels are increasing.
The main principle to remember is this: the hot bed’s decline in temperature must coincide with the longer days of mid- to late March. By this time the worst of the weather should have passed and longer, warmer days and shorter nights are compensating for the loss of heat in the manure.
Side view of hot bed with growing frame and light. The outer frame should be at least 180cm × 180cm (6' × 6'); the growing frame at least 120cm × 90cm (4' × 3').
The growing frame sits on the manure, part-filled with soil or compost, with a cover of glass or polythene. The frame is usually made of wood with a thickness of at least 2.5cm (1"), which helps to retain the heat and keeps out frost. The cover, known as the ‘light’, ‘or ‘lights’ if more than one, also retains heat and keeps out rain and snow. The growing medium – the soil or compost – inside the frame is thus kept warm, moist and not saturated, and the air within the frame is also warmed by the constant heat rising from below. Ventilation is provided by raising or removing the light. In essence: The stable litter or other organic material used in the hot bed drains well, so the growing medium above it also drains well.
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16 Hot Beds
CHAPTER 2 How hot beds work 17
January l
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Turn the old hot bed again or purchase compost in readiness for
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frames. If you are making large hot beds, continue to purchase or collect manure until the middle of the month. If making small hot beds, collect or purchase a load of manure at the end of this month. (Large hot beds take longer to build so you need to allow more time!) Make up the hot beds, large or small, in the last week of January, with the aim of sowing in the last few days of this month. Make sure you allow adequate height of hot bed, as it will need to provide heat for several months. For a small hot bed, sow a combination of carrots, spinach, radish and rocket or salad leaves, or, if lettuces have been grown from October, plant these out and omit the rocket or salad leaves. If you have a large hot bed with multiple frames, include the abovementioned crops and also sow or plant potatoes, beetroots, onion sets, lettuces, turnips and spring onions. If you are planning a hot bed with alternative materials, wait until next month before making it.
March l
Make alternative hot beds in early March if you haven’t already done so, and sow up as for a January or February sowing.
Plant potatoes in pots if you wish, for planting out in April. l Previously sown crops will require more air now; there will be more l
favourable days to remove the lights, but they must be returned at night. l More water is required, so allow rain to enter the hot bed. Ensure that the lights are closed again at night and protection given if frost is forecast. l Early in the month start harvesting radishes, rocket and salad leaves. Lettuces planted in late January to early February will be ready late in the month, as will turnips and occasionally potatoes. Be wary of frosts, particularly with potatoes. l When gaps appear, sow more radishes, rocket, salad leaves and spinach.
February l
If any of the January tasks have not been completed, then do them
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early in the month. Germination will be fast – give more air when necessary and on favourable days remove the lights for short periods. February is often the coldest month, so keep bubble wrap close by to insulate with if necessary. Keep an eye on watering, as some crops will be growing away at the end of the month. Sow early leeks on a vacant bed. If you are making a hot bed with alternative materials, it can be done at the end of this month.
76 Hot Beds
Late March: rocket has been harvested, making room for carrots and other crops. Leeks are to be planted later, between carrots.
CHAPTER 6 Planning and sowing 77