This plant was known for years as Spiraea Japonica, and by the commercial florist is still almost universally called spiraea. It is a perfectly hardy herbaceous plant, and there are few plants so hardy or that will stand more rough usage than this astilbe. On dry, sunny borders the feathery spikes are far less beautiful than those we grow under glass, but I have seen some very fine spikes this spring on plants that were in deep, moist soil and partially shaded by trees. It is, however, as a pot plant or for cut flowers in early spring that we are most concerned with the astilbe. At Easter, though by no means so profitable as many other plants we grow, they seem almost indispensable, and again on Memorial day they are in good demand. When used for cutting we find the flower is not the only useful part of the plant; the foliage is always cleanly used up in cheap bunches of flowers.
The clumps of roots that we force are all imported from the rich, fat lands of Holland, and so long as the Holland growers can supply them so cheaply it will never pay us to bother with their cultivation. They usually arrive about the middle of November and should be unpacked and placed in flats or boxes with an inch or so of soil or litter over them. Then give them a good soaking and place the boxes outside, anywhere.
The astilbe can be forced into flower in eight weeks by giving it great heat, but I much prefer giving them twelve weeks, and the first three weeks they can be under the bench. If not previously done, when potting them give the roots a good soaking; there is such a thick mass of roots that the ordinary watering does not thoroughly wet them. They are the simplest of all plants to force. Pot them into 5, 6 or 7-inch pots, or whatever size will hold the roots. A temperature of 55 to 60 degrees at night will suit them better than a higher one. Water is the great essential, for by the flowering time the little soil that you give them is one mass of living, hungry roots. It is labor saved and far more satisfactory all around to stand each pot in a 7 or 8-inch saucer, in which keep a constant supply of water, and if this is weak liquid manure your plants and plumes of flowers will be much finer.
The astilbe is not troubled by aphis, spider, thrips, or any other of our pests, but when the growth is young and not matured they are easily burned by to-bacco smoke and that must be avoided, either by covering the astilbe, or giving them a good syringing, before you fumigate, or best of all, don't have them in a house that must be fumigated.
The old form A. Japonica is still largely grown. A. compacta has rather dwarfer and denser spikes. The Gladstone is a very fine variety and so is the Washington. There is also a variegated form of Japonica of dwarf growth and of no commercial value except for its variegation.
Those wanted for Decoration day we keep out of doors till middle of April; they come into flower easily in a few weeks thus late in the season. When sold to a regular customer you will do well to either sell or give with them a 7-inch saucer with instructions to place under the pot and keep water in it. If this is done the astilbe will be satisfactory, otherwise it will shrivel up.