This section is from the book "Window Gardening", by S. T. Maynard. Also available from Amazon: Window gardening.
Plants that have grown too large for the pots, so that the roots almost literally fill the earth, should be put into a pot of a larger size, and fresh soil added. The old soil should be picked out from the outer edges of the roots, care being taken not to break the roots too much, the object being, in repotting, not only to give a larger-sized pot and renew the soil, but to make the soil lighter and more porous about the roots,the same as is done in cultivating land. When the plants do not respond to watering or enriching, it may be due to one of two causes,—either the soil has become sour and unhealthy or they need repotting. Plants should be taken up in the fall, before the severe frosts, and placed in pots with as much earth as possible clinging to the roots. Crowd the earth about the roots so that the plant will stand up, and water as usual. In repotting or taking up plants, the soil should be enriched; and this is best done by adding a teaspoonful (not heaping) and ?io more, of Bowker's Ammoniated Food for Flowers to a .two-quart pot, thoroughly mixing it with the soil, and at the same rate for larger or smaller pots.
 
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