This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
NEXT in importance to a site for a garden is that of the position of hothouses. The position in which hothouses are placed in relation to the surface of a garden, and to other offices in connection with a garden establishment, is of very great importance, from both a cultural point of view and the ease and efficiency with which all the operations connected with the culture of plants and fruit can be carried on.
Although the ordinary architecture of fruit and plant houses is not by any means ornamental - and the less so and more simple they are in their construction the better as a rule they are adapted for plant and fruit culture - yet the appearance of a range of glass-houses, even in relation to a vegetable and fruit garden, is a point which should not be ignored so utterly as it has been in even the most pretentious gardens. Indeed, next to the seeming perversity in choosing a site for the garden itself, is the higgledy-piggledy manner in which glass-houses have been scattered about, as if they had been abstracted in an " inconsiderate rage " from a Pandora's box, and scattered about to create the best, or rather worst confusion, and to be as inconveniently heated and difficult and laborious in their management as possible. We could refer to numerous illustrations of defective arrangement not only in choosing the locality of hothouses, but in the relation in which they have been placed the one to the other.
And some of these illustrations, strange to say, might be got from establishments of a purely commercial character, where glass-houses are erected to grow fruit and plants for sale, and where it might be expected arrangements that are calculated to reduce the expenditure of fuel and manual labour to a minimum ought to be a matter of the first importance, but where, instead, inconvenient arrangements and expensive working must reduce the profits very greatly indeed.
One of the most striking instances of blundering in connection with the recent erection of a quantity of new glass came under our notice a few days ago. Evidently the proprietor was in the humour for a very liberal expenditure in the way of graperies, etc. To the site chosen no very particular objection can be urged. It was a level piece of ground lying on a very deep subsoil of strong clay. A range of 300 feet of vineries was one of the items decided on. And, wonderful to tell, an immense excavation, sufficient in length and width for the whole houses, and their borders, was excavated to the depth of 6 feet, and in this level are the vineries and borders placed. Literally buried out of sight to a great extent; and the result is damp ! damp! and mildewed Vines. To increase the grotesqueness of this arrangement, a series of span-roofed houses is perched on the natural ground - level, right in front of these semi-subterranean vineries. And in heating the sunken range the boiler is placed at one end of the range instead of in the middle, to work right and left and simplify the arrangement of pipes.
We know of plenty of old hothouses which have been foolishly sunk in damp subsoils, but could scarcely believe our eyes when we saw the modern range in question.
This sinking of hothouses so much below the ground-level is always an error attended with many evils. To say nothing of the dampness for a great portion of the year, sunken houses are most inconvenient to work, from the fact that several steps have to be ascended and descended every time they are entered for any purpose whatever. If there are to be steps at all they should be upwards; but even then, in ordinary cases, there should not be more than one. Another great evil attendant on sinking hothouses is, that they necessitate deep stoke-holes that are difficult to drain, and inconvenient in many other respects.
When there are many glass-houses, they should as a rule be placed compactly together and in parallel lines, and varying very little in their base-levels. They are thus much more easily heated and conveniently attended to in every respect. Another matter which saves much labour and time in working hothouses is the manner in which efficient ventilation is provided for. The way in which this very important matter is arranged in some cases is very simple and effective; in others it is the very reverse. We recently inspected a new range of glass, 300 feet long, composed of lights 4 feet wide, in which the ventilation was effected by letting down and pulling up every light separately with a rope ! and where the whole front had to be opened in the same clumsy inconvenient way. It is almost incredible that such a mode of ventilating should be adopted at this era of hothouse building.
Any system of ventilation that necessitates the moving of half or the whole of a roof to give a few inches of ventilation, is wrong in principle and most laborious in practice, and should not be tolerated for a moment. It is not our intention here to enter into the desirable minutiae of hothouse arrangements. "We desire to point out a few errors to be avoided, and would recommend all who contemplate hothouse building, and who do not employ practical gardeners who are up to the times in these matters, to secure the services of some competent practical gardener as their adviser. Builders do not understand the requirements of plants and fruits, and commit great blunders in such matters; and it would not only save gentlemen much annoyance and disappointment, but it would ultimately save them much money to do as we advise.