But to come back to big displays with rock plants that any one can have, I believe that we shall make a great and peculiarly American success by emphasizing summer effects. In England, the rock garden is a spring garden. True, there are lovely bits of colour in it all summer and autumn, but the whole thing is a blaze of colour only in spring. In America, summer is the national play time. Our great annual exodus to the country does not come until hot weather, or say June; and our great vacation month is August. What we seek then is coolness, comfort, rest.
Now the coolest colours are white, green, gray, and blue. The hottest are red, orange, and purple. So I think we should avoid big masses of scarlet sage, red cannas, cerise geraniums, and other things that make us feel the heat, and plan to have broad sheets of dainty little white flowers like snow in summer, white tufted pansies, fragrant pinks, sweet woodruff, white rock-cress, and the common alyssum, which, though annual, sows its own seed.
The question of greenery on the rocks in summer is highly important and peculiar. The great fault of rockeries everywhere is that they show more rocks than vegetation, and that is why they look hard and hot in summer. But if there is too much vegetation the rockery will look coarse and weedy. Every thing in the rock garden must be daintier than in any other kind of gardening. We want no tall bushes or perennials, because we do not wish luxuriance of height, but of spread. So I believe we shall get an important American element in our rock gardens by using American ferns that have a talent for spreading among rocks and give a feeling of coolness in hot weather.