THE USE OF ORNAMENTAL PLANTS 305 



several species, the more common being probably Philadelphia 

 coronarius. The shrub is deciduous and the species mentioned 

 above grows to a height of eight to twelve feet. The flowers 

 are white with yellow centers and, while they resemble in a 

 general way the flowers of the orange (hence the name mock 

 orange), they are much larger and more showy. 



The members of this genus are found in widely separated 

 parts of the world; some of the forms come from China, some 

 from the Himalayas, others from Mexico and still others are 

 wild in the United States. 



429 . Hydrangea is essentially a shade-loving plant . There 

 are many different forms, most of them shrubs, but a few are 

 climbing vines. They are deciduous and are characterized 

 by rather large leaves and flowers borne in dense heads or 

 clusters. These flowers are commonly pink in color but they 

 can be changed from pink to blue by the addition of iron or 

 lampblack to the soil. The hydrangea is propagated readily 

 from cuttings and grows rapidly but require.8 a fairly moist 

 and rich soil for best development. Most of the ornamental 

 forms should be pruned rather heavily every winter and some 

 of them are rather susceptible to frost. The species should, 

 therefore, be selected with some care, keeping in mind the 

 experience of the individual community. 



430. Trees. So many trees are suitable for landscape- 

 gardening purposes that it is out of the question even to 

 attempt to suggest a few as being preferable to others. The 

 oak is found in all the parts of the United States. There are 

 both deciduous and evergreen species and the plants differ in 

 size from small shrubs to very large trees. A number of 

 plants bear the name of oak which in a botanical sense have 

 no relationship whatever. Poison oak, for example, belongs 

 to an entirely different group of plants, and Australian silk 

 oak, technically known as Grevillea robusta, does not even 

 resemble the oak with respect to flower, leaf, or habit of tree. 



There are several kinds of elm, some of them native to 



