Where these broad-leaved evergreen shrubs will flourish out of doors there is no hardy shrub that equals them for color and massive beauty. We have seen acres of them growing as freely as a weigelia or philadelphus, and in many parts of Great Britain they are planted for game covers, but that is on the other side of the Atlantic. In the vicinity of Boston they appear to do well, and nearer home I have seen some large, healthy plants, but in this immediate neighborhood they are a failure. Thousands of dollars have been spent for their purchase and care, but in a few years they are gone. We have pulled up this spring the remains of rhododendrons and kalmias (and replaced with hardy deciduous shrubs) which the confiding owner had purchased from the agent, who showed him the gorgeous picture of a rhododendron warranted (till the bill was paid) to grow and blossom even more beautifully than the colored plate. So be careful, and unless you are sure that these plants thrive in your neighborhood, don't sell them. There are any number of good, honest, hardy shrubs.
It is said that the rhododendron, or any of the Ericaceae order, will not thrive where the soil is impregnated with lime. So there cannot be lime in some parts of the Alleghany mountains, for there the kalmias cover the mountain side. R. Catawbiense is widely distributed through our eastern states, and is quite hardy. There are other causes than the lime that make the rhododendron an undesirable plant for our northern states. It gets burnt with the bright suns of March when the leaves are frozen hard. The past winter has destroyed many.
It is as forcing plants that we are chiefly interested in them. They take up much room and we have several times declared we would leave them alone, but as the drummer pays his annual visit we relent and say: "Well, we will try just a few." And it is only a few you want in the commercial greenhouse; and the best time to have them is at Easter. For the past two or three years well flowered rhododendrons of medium size have sold well.
The rhododendrons that you see planted by the landscape gardener (especially if he is from a distance), and those we buy to force, are varieties of R. Ponticum. They are propagated from seed, by cuttings of the half-ripened wood, by layers and by grafting. The last method is the usual one to increase the fine named varieties. The business of propagating and growing the rhododendron is a specialty with those who have the suitable soil, such as the fine peat of Surrey, England, or the black peaty soil of Holland and Belgium.
If I attempted to grow on over summer any rhododendrons I would use two-thirds of turfy loam and one-third well rotted leaves. You could not, however, begin to grow them a season as cheaply as you can purchase fine young plants, well set with buds, that only need a few months' care, like our newly imported azaleas, with this difference, that you must expect to sell or give away all your rhododendrons, while your unsold azaleas are, with proper treatment, much better plants the second year.
When potting the newly imported plant see that the ball is not too dry. It is better to make sure by dipping it in a tub of water. Pack the soil firmly around the old ball and store the plants away in the coolest house or frame you have. At New Year's, bring them into more heat. We failed several years to get them into flower, thinking that like the azaleas they would come along in a cool house. They won't do it; you must give them 60 to 65 degrees at night and syringe them daily; in fact, it is heat and moisture that bring them out. They may not need three months to force them out, but it is well to be in time, and be sure to give the roots plenty of water, particularly when in flower. The flowers wilt easily in the sun if the roots are dry.
Bed of Callas.
There are countless varieties, but some of the handsomest do not force well; so in ordering see that the varieties are suitable. Desirable forcing varieties are now largely grown for that purpose.
When you realize that the rhododendron is perfectly hardy, you will understand better the treatment the plants need before you start to force them. You will frequently see them put at once into the greenhouse, perhaps at a night temperature of 50 degrees. This is waste of room and is uncalled for. A cold shed or coldframe where shading can be applied is just as suitable for them, but when you do start to force they need a brisk heat.
There are now beautiful hybrid rhododendrons, the offspring of several species, which make fine conservatory plants. They should be managed as we do azaleas, without the severe pruning. After flowering they make their growth and should be encouraged to grow by a good heat and moisture. When you see the buds set you can plunge them out of doors for the summer and remove to a cool house when you do the Indian azaleas.