This section is from the book "Indoor Gardening", by Eben E. Rexford. Also available from Amazon: Indoor Gardening.
MANY amateur gardeners are under the impression that their plants need feeding when they begin to languish, or when they show a disposition to rest, and the first thing they do is to apply a fertilizer of some kind, generally in considerable quantity, on the principle that if a little is good a large amount must be a good deal better. The result is, nine times out of ten, that the plants are injured rather than benefited, because they are not in a condition to make use of a fertilizer. It is not more food that is needed at such times-rather, as little food as possible, in order to give the digestive organs of the plants an opportunity to regain the tone they have lost, to some extent, by overwork, until a sort of general exhaustion has taken place. The application of a rich food, at such a time, may force growth, but it will be an unhealthy one, since it is secured at the expense of the plant's vitality, and almost invariably this unnatural growth is followed by a reaction disastrous in the extreme. The effort on the part of the plant to properly digest and assimilate the food increases the trouble precisely as over-eating affects the human stomach when in a weakened condition.
There is one rule regarding the use of fertilizers that no person who would be successful in the culture of plants can afford to overlook, and that is this: Never apply a fertilizer of any kind to a plant that is not growing.
If growth is just beginning, after a period of rest, let the amount of fertilizer used be in proportion to the growth being made. Keep in mind the fact that what is needed is not a rapid development, but a sturdy one, and be satisfied with a healthy growth. Rapid growth almost invariably means a weak one, from which, as has already been said, a reaction may be expected, after a little.
Never force a plant.
I am aware that many a reader may say here: "Why doesn't he tell us just how much fertilizer to use ? How are we to know this ?" To which I reply: You must exercise your judgment in the matter. Begin with weak applications and observe their effect. If the plant grows well, you are giving enough. As its development increases the plant will be in a condition to make use of larger amounts of food, and you must increase the supply in proportion to the development being made. Just how much this will require is something that no one can determine without seeing the plant. Nothing but personal observation can solve the problem of how much or how little fertilizer to use.
And personal observation only can tell you when to use it. You must learn to rely upon yourself largely in caring for your plants. Keep that in mind, always.
Another reason why definite instruction regarding quantity can not be given is-fertilizers vary in strength, and since there are many kinds on the market, and the writer cannot know what particular kind you propose to make use of, it is impossible for him to say anything about amounts except in general terms. Here is where observation and good judgment must again be made use of. Let me say this, however, keep on the safe side by using small quantities until you have learned the effect of whatever fertilizer you make use of. Experiment cautiously, and be always on the lookout for results.
There are, as has been said, a great many fertilizers on the market, advertised as plant-foods in most instances. Great merits are claimed for them, and amateur gardeners who are ambitious to make their plants excel those of their neighbors are tempted to invest in them. Some are really good, and others are positively bad, because, instead of being really foods they are simply stimulants. Their use may excite the plant to action, temporarily, but reaction is sure and speedy, because the energies of the plant have been spurred to a degree not warrantable by the vitality of it. Such so-called "foods" and fertilizers ought not to be used. When you read of any advertised to do wonders among the plants in your window, do not give them a trial until you have assured yourself of real value in them, and this can only be done by letting some one else give them a test. If you wait for this, the probabilities are that you will not make use of them, for those who test them seldom feel justified in giving any testimonials in their favor.
"But," some one may say, "how are we to guard against frauds ? How are we to know the good from the bad?" I reply, make use of such fertilizers as are sold by reliable florists and seedsmen who have established a reputation for honesty and fair dealing that they cannot afford, even if so disposed, to take advantage of a customer's ignorance and palm off upon her a worthless article. Such dealers make a point of handling only the things whose merits they are sure of.
The basis of nearly all our best plant-foods is bone-meal. This can be bought very cheaply and I have found it about as satisfactory as anything I have ever used. It can be mixed with potting-soil, or it can be supplied to a plant at any time by digging it into the soil in such quantities as may seem advisable after we have become somewhat familiar with its effect. When used in this manner it will not be necessary to repeat the application for some time, as it does not immediately give off all its nutritive qualities. The finely ground meal should always be used for pot-plants. (The coarse article is too slow in its operation for such use.) Those who have never used it may safely begin with a teaspoonful to a seven- or eight-inch pot. Watch the result and do not apply more until you are sure it is needed. The enthusiastic amateur generally overdoes this matter in his desire to see his or her plants make strong development, and quite often he kills by kindness.
Another most excellent fertilizer is manure from the cow-yard. This is, of course, only available for those living in the country, but those who have facilities for obtaining it need not wish for anything better. If used in dry form it can be mixed with the potting-soil, after being pulverized as finely as possible, or it can be applied as a top dressing to the soil already in the pots. Care should be taken to select that which is so old as to be black and friable. Never use the fresh article. If you care to use it in liquid form put the unpulver-ized manure in tubs or barrels and pour on enough water to cover. Allow it to soak until you feel quite sure its strength has been extracted. Add enough of this infusion to the water you apply to your plants to give the latter the color of weak tea. This operation can be repeated as often as seems necessary. Such a fertilizer is a safe and satisfactory one if not given in great strength.
You will frequently read about the advisability of applying oil to the roots of your plants in order to bring about a vigorous growth. Such advice is dangerous. Oil will form a coating over all roots with which it comes in contact, and make it impossible for them to take moisture properly from the soil, as oil and water repel each other. The result of applications of oil will surely be diseased plants.
Sometimes we read that beefsteak will greatly benefit a plant, if applied to its roots. There may be some nutriment in decaying flesh, but not enough to warrant its use as a fertilizer. The probabilities are that it will breed worms to prey upon the delicate roots of the plant to which it is applied. The offensive odor given off by it, as it decays, renders its use objectionable if it had all the merits ascribed to it by those who take stock in whims of this kind.
When plants have been repotted in soil prepared as advised in the chapter on pot-ting-soil, it will not be necessary to use any fertilizer for some time, as there will be as much nutriment in the soil as will be required by the plant for quite a period of growth.
Soapsuds can be made use of when other fertilizers are not at hand, with fairly good results, if care is taken to dilute considerably. An application of this kind often acts beneficially when there are worms in the soil.
The old belief that it was absolutely necessary to give a plant a larger pot and fresh soil at least once a year has been largely abandoned since the use of liquid fertilizers has become common. By applying them regularly, in moderate strength, it is possible to keep a plant in the same pot, and same soil, year after year, and this, too, in a healthy condition. If it can be constantly supplied with nutriment, it does not seem to matter very much whether that nutriment comes by way of a soil containing the various elements of plant-life or in the shape of a liquid easily appropriated by the feeding-roots and quickly assimilated by the plant. The food, and not the manner by which it is obtained, is the main thing. The writer has an Aspidistra, growing in a twelve-inch pot, which- has not been repotted for over eight years. Nor has it been given any fresh soil during that time. Its roots are in a solid mass, and have been in that condition for a long time. It throws up many new leaves yearly, and does not seem to suffer in any respect whatever from failure to receive new soil or more root-room. He has also a Fern-an Adiantum-which has not been repotted or furnished with fresh soil for several years. Both these plants have been fed with weak applications of liquid manure, and the result has been most satisfactory. The use of fertilizers on old plants does away with a large amount of work by making it unnecessary to repot frequently, and it economizes space, as it makes it possible to grow good-sized plants in smaller pots than it has heretofore been thought safe to use.
At no time should plants treated as mentioned in the preceding paragraph be given strong applications of liquid fertilizer. Let it be rather weak, but apply it frequently, and regularly. Too strong an application will be likely to excite a growth which is not desirable on the part of a plant already of good size. The aim should be to give simply enough nutriment to keep the plant in healthy condition.
 
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