This section is from the book "The Gardener V2", 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.
If any one were to calculate the labour and expense incurred in one year in combating those insect pests and diseases which beset the gardener in every department of the garden, it would be found to be a very large item, indeed, of the general expenditure. And it is a question of serious import to the gardener, whether all the scraping, scrubbing, painting, etc, which has for so long been considered an indispensable part of the yearly routine of garden-work, is really so efficacious as to justify a continuance of such measures. I have a strong impression that with many the subject is a matter of faith, and not of experience; and that they would only be too glad of an excuse to get rid of their belief, and a labour of the most irksome kind, which can often be ill afforded. At all events, it was while pondering the matter over in this light about three years ago, and making a calculation of the probable time and labour required to clean and dress a considerable range of vineries and peach-houses, and which could not be well afforded at the time, that we determined to disregard all advice and preconceived notions on the subject, and strike out of the usual track, for a season at least, and risk the consequences.
The houses were of course washed down with the syringe for the sake of cleanliness, and to remove obstructions to the light; and the Yines and Peaches, early and late, were tied up after pruning without any cleaning or washing whatever. The result was that in the following season we were just as free from spider and thrip as before, and gainers upon the whole to a considerable extent in time and labour. Since then we have never dressed either our Yines or Peaches as a protection against insects, not even cleaning the loose bark off the Yines, except where actually unsightly; and the result in every case has always been perfectly satisfactory: nor have we any intention of doing so again; and, I fancy, no amount of reasoning would prevail upon us to alter our determination, so convinced are we of the needlessness of such measures. No doubt it will be argued, as an arithmetical question, that if ten thousand red-spider are destroyed while in the embryo state in autumn, there will be that number less to contend with in summer - a very plausible demonstration, I admit, and one which I am quite willing to leave unanswered.
I will only set the practical experiment against it; but this I will assert, that even although the most rigorous system of cleaning had been adopted, it would be an easy matter to produce the pest with marvellous rapidity. Red-spider is worse in some seasons than others; and it might naturally be expected to be worse the season following, but such is not the case, for it as often happens that Yines which have suffered one year are comparatively free the next. Through the hot summer which we have just passed, our Peach-trees have been wonderfully clean. As a rule, our late vineries are generally quite free from spider; and in some of our earlier vineries the Yines retain their leaves healthy and green long after the fruit is cut and the wood hard and brown.
The above remarks apply chiefly to winter-dressing. We are not without faith in some specifics, but after trying a good many nostrums, we have fallen back upon sulphur as our best friend. Applied either with a syringe or a duster, there is no doubt about its efficacy in cases of mildew, red-spider, or thrip; but our great panacea for the ills we have described, and many others, is healthy root-action. We have great faith in copious waterings, good drainage, and a discreet use of liquid manure. I am inclined to think that many of the failures which have been attributed to heated or aerated borders could be traced to neglect on one or other of these points. I could not say that I ever saw any noticeable effects produced by sprinkling guano-water, or ammoniacal liquor of any sort, upon the floor as a preventive against insects; but I have not the least doubt about the good effects of liquid manure when applied to the roots - and it seems to be very energetic in its action, indeed. Strong doses applied to pot-Vines, Melons, Cucumbers, or French Beans, that are affected with spider or thrip, will often eradicate them sooner than anything else.
There seems every reason to believe that insect and parasitical attacks are, with a few exceptions, a consequence of ill health arising from some other cause. Keep up the vital energy. Thorough ventilation, full exposure to light, a moderate temperature, judicious watering and mulching, will effect more than all the scrubbing and painting in the world. Our Vine-borders here are all well drained. Some are aerated, and chiefly inside; but we mulch thickly inside and out, and are so impressed with the importance of watering copiously, that we have had our tubs and cisterns raised, so that we can run the tepid water off through a hose on to the border in a copious stream, and deluge the border in a few minutes. The result is - and I hope I will be excused for saying so - that the crops are always excellent, and shanking is quite unknown. The mulching keeps the roots so close to the surface, especially in the aerated borders, that you can scarcely shove a pen-knife into the border without bringing a bunch of fibrous roots to the surface.
It has been argued, somewhat confidently, that spider, green-fly, and suchlike pests are the natural concomitants of plant-life under any conditions, and rather undue importance has been attached to the efficacy of the smoking-pan, the virtues of tobacco, and other measures of the same kind; but I would rather not encourage a reliance upon such auxiliaries, and would be inclined to look upon their too frequent employment as a sign of bad generalship. One of the most fertile sources of disease among plants is the crowding those requiring different temperatures and modes of cultivation into one house. Many gardeners and employers insist upon having plants of all kinds, whether they have accommodation or not; and into one of the two extremes they must go - the greenhouse or the warm stove. Where collections of plants are desired, an intermediate house is indispensable a common ground on which the stove and greenhouse can meet in summer or in winter; and what a convenience to the gardener ! But there are very few places as yet where such a convenience exists, although its importance is daily becoming more pressing. The plants that will not grow in a greenhouse, and which would only linger out a miserable existence in a stove, are too numerous to mention.
Mexico, New Holland, and the Cape would furnish a whole host of the most beautiful and useful plants in cultivation. That gem, the Luculia gra-tissima, too frequently seen long, lanky, and forlorn-looking in a stove, or contending for very existence with cold and green-fly in a greenhouse, is worth a house itself; and beside it would nourish many of the fine Ferns, Orchids, and other plants that are crowded in out-of-the-way corners in our stoves and greenhouses, not to speak of Oranges, Palms, Cycads, Begonias, Caladiums, Passion-flowers, Gardenias, and innumerable others. The New Holland variety of that fine Fern the Neotopteris, or Bird's-nest Fern, when grown in a stove, where it is frequently seen grey with thrip, or scrubbed and washed out of its original beauty and characteristics - a perfect caricature - is a continual protest against the conditions under which it suffers; but change it to the intermediate house, or a sheltered corner of the greenhouse, let it have plenty of water and shade, and it will take care of itself, and manifest no disposition to disease.
The finest plant of this kind I ever saw, about 6 feet across, with leaves that almost rivalled in breadth and substance the Musa Cavendishii, grew in a cool conservatory beside Camellias, where the winter temperature was seldom above 40° or 45°. If time permitted, numerous instances could be furnished, showing that many of the diseases to which plants are subject are the result of functional derangements, or impaired vital energy arising from other causes. British Queen Strawberry and its kind are more subject to spider than others, as also the Frontignac Grapes and other weak-growing kinds. Black Prince Strawberry, Royal George Peach, some kinds of Roses, and certain varieties of the Verbena are very liable to mildew, as there are others which are peculiarly exempt. And the same curious and significant facts are observable among various kinds of Pears, Apples, Plums, and vegetables - as a rule, the weakest always going to the wall.
J. S. Wortley.