This section is from the book "The Gardener V3", 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.
In the successful management of plant-houses nothing is so necessary as courage - courage to avoid worthless varieties, courage to throw inferior plants away, and courage to give those which are retained room sufficient to develop their proportions in a proper manner. Nothing is more common in arranging the plant-houses at this season, than for the best to be staged first, giving each fair breathing-space, leaving the inferior specimens until the last. Then it is that courage is required to throw them away, instead of crowding them into the house, to the certain injury of better things. But, oh no ! This is deliciously sweet; that will have a few flowers about Christmas; and a third belonged to my dear Somebody, and must be kept. Thus the dying are crowded among their more healthy brethren, each is deprived of the space necessary for existence, and all become more or less unhealthy. This is in plain English the secret of the failures of three-fourths of the gardeners in the country, practical as well as amateur. They convert their plant-houses comparatively into mere Black Holes of Calcutta, where plants are crowded together until the weaker ones become fairly suffocated.
Of this we require no stronnger evidence than the sight of the long, lean, lanky things which crowd many plant-houses in the country, and which when taken out are too weak and attenuated to stand alone. To regard such things as plants in the proper cultural sense of the word requires a stretch of imagination and credulity only to be attained by the profoundly ignorant. Our rule, directly a plant becomes unsightly in itself, is to commit it to the rubbish heap; flowers at the cost of an unsightly plant have no charm for us. The first consideration before removing plants into their winter quarters is to take care that those quarters are thoroughly cleansed, the glass and woodwork washed with soap and water - the latter painted if necessary - and the stone or brick work washed with hot lime, to which a handful or two, according to the size of the house, of sulphur may be added. The advantage of this washing is, first, the routing or destruction of insects and their ova; secondly, more light; and thirdly, as the consequence of cleanliness, a sweet and wholesome atmosphere. This cleanliness must extend to the plants and the pots which they are growing in. The latter must be divested of every particle of dirt by means of the scrubbing-brush, and, if necessary, sand.
Sometimes pots, if not properly baked, have a soddened, heavy appearance, quickly become green, and in these the soil dries but slowly. A plant so situated may be compared to one growing in ill-drained land; the water does not pass away with sufficient rapidity, and consequently there is not that free circulation of air through the soil which is indispensable to perfect growth. Such pots should always be removed - in fact, destroyed - and be replaced by clean pots of the proper size. At the same time clear any wet soil from the surface of the pots, not necessarily digging down so as to disturb the roots, but just taking away that surface-skin upon which confervse or other water weeds may have collected. Always replace the soil with compost of the same quality, and do not, because you have peat at hand, use it when you ought to apply loam. At the time of surface-dressing it will be wise, should the earth in any of the pots appear soddened, to turn the plant out and wash the inside of the pot, or, what will be better, put the plant into a clean, dry pot of the same size. At the same time, make two or three holes vertically through the soil with a thin pointed stick, and, with cautious watering for a short time after the top-dressing is applied, the soil will soon regain its wonted porosity.
These may appear trifling details, but it is upon such that perfect success in plant cultivation depends; in fact, they form the main portion of that cleanliness without which perfect success is impossible. If you visit the establishments of any of our great plant growers, as Baines, Cole, Ward, Turner, Williams, Paul, etc. etc, you will find their plants and plant-houses as clean as a drawing-room and its furniture, with persons washing the leaves of the plants, and removing every speck of dirt with as much care as it would be removed from the most beautiful painting or piece of statuary. This may be called the refinement of cultivation, but it never yet has been carried too far. Plants live by a respiratory process, just the same as animals; they are influenced by good or injured by bad air, precisely in the same manner. What Professor Tyndall regards as the dust of the world, or the "stirabout" of our atmosphere, chokes the breathing pores in the plant just as it does ours; and if they are not washed, the plants are affected just as we should be under the same circumstances - their natural economy is disturbed, and they suffer accordingly.
Thus we find that smooth and rather large leaved plants - Planes, Aucubas, Camellias, Myrtles, Indiarubber, and the like - always succeed better in the smoke of towns than the small-leaved plants, as the Coniferae, Heaths, and woolly-leaved Pelargoniums, Cinerarias, etc, as these collect the dust and hold it, rain only tending to increase its tenacity; while upon the smooth-leaved plant every shower washes it away. This is the simple history of the natural condition of foliage to resist the injurious consequences of a bad atmosphere. Last year, from November until the following spring, we had in our sitting-room a plant of the beautiful-leaved subject Dracama ferrea terminalis, which, washed twice or thrice a week, resisted the evil effects of a gas-poisoned atmosphere, and looked well at the last. During the same time scores of Primulas, Cinerarias, Violets, and Mignonette, perished in the same place. Having thus far explained the reasons why plant-houses should be kept perfectly clean, we will only remark that, before large plants be taken into their winter habitation, it would be well that each should be laid upon its side and thoroughly washed by means of the syringe or garden engine; and when we say washed, we do not mean merely sprinkled, but the water applied with such force as to wash the foliage thoroughly clean.
For this purpose it will be best to lay the plants upon a clean pavement, or, if that cannot be had, then lay a clean mat for them to rest upon. Apply the water with full force to the stem of each plant, and in that manner the pores will be opened, and the health be materially improved. The plants being cleaned, there is a point or two to be considered in their arrangement. Some in the greenhouse, for example, such as Heaths, Epacris, and Acacias, will bear any amount of exposure, while to Tropseolums, Boronias, Leschenaultias, Gompholobiums, a cold draught is almost certain death. Hence in arranging the house it will always be best to place the last-named section in the warmest part, where they will get a free circulation of air without a cutting draught. Then, again, in the ordinary greenhouse you have hard-wooded as well as soft-wooded plants to accommodate. The latter will generally be found the most susceptible to cold, and must be provided for accordingly. The fact is, the more hardily plants are treated from this time the less likely will they be to sustain injury through the winter; and hence, observing the rules we have laid down, it will be manifest that, secured from frost and the cold draughts we have spoken of, the more air a greenhouse receives the better will it be for the plants.
Never apply a fire until it is necessary to exclude frost, and then use no more than may be requisite to maintain the desired temperature. W, P. A.