This section is from the book "The Complete Garden", by Albert D. Taylor. Also available from Amazon: The Complete Garden.
Perennials need a great dealof food- and should have plant food to restore soil fertility. Such heavy feeders as phloxes and peonies should receive applications of bone meal and liquid manure. Such applications when the plants are in bud will frequently improve the size and quality of the flowers. Manure for fall mulching will also enrich the plants. The finer part can be worked into the beds during the spring, but care must be taken not to injure or destroy roots or smaller plants. Peonies and irises in general, like all plants with thick, fleshy roots or rootstocks, are sickened by manure. Bone meal is perfectly safe to use and is in every way the best fertilizer for them. On the other hand, the Japanese irises, with their fibrous roots, revel in cow manure. They, like iris longipetala, are indifferent to lime which to all other moisture-loving irises, with the exception of the spuria group, is objectionable.
Beds must be kept entirely free from weeds until fall. Where mulch is not maintained around the plants cultivation should be kept up, especially after a rain, to prevent evaporation.
In the development of the annual flower garden the soil should be thoroughly spaded over each spring and well pulverized. A good coating of well-rotted manure should be thoroughly spaded into the soil to a depth of four inches to eight inches. During the flowering season of these plants it may become necessary, on account of the lack of sufficient food, to supply some quick-acting fertilizer such as sheep manure or dried blood which will force their growth and assist greatly in developing larger and more abundant flowers. A slight sprinkling of sheep manure or dried blood around each of the plants will be sufficient. It may be advisable to repeat this fertilizing operation at intervals of three or four weeks during the flowering season. Nitrate of soda is sometimes used as a plant stimulant. It is much more dangerous, however, than either sheep manure or dried blood because an overdose is very apt to burn and injure the plants.
 
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