Here is a sample: salvia for red; dwarf marigolds for orange and yellow; carrot foliage for green; bush morning glories for blue; and dwarf petunias for violet. Color-illustrated catalogs will suggest other possible choices. Just be sure the colors are true hues.
If you plan this for late mid-summer you should have no trouble making selections that will eventually be in bloom together. Naturally they won't all pop into blossom at the same time, but watching the rainbow colors light up, one by one, will be part of the entertainment.
Children momentarily enchanted with tiny things should be delighted with some of the midget versions of your own grown-up vegetables. Many miniature vegetables, bred for the small garden, are equally appropriate for the small gardener. There are a host of them, and new ones arriving every season-Tiny Tim tomato, midget corn, midget watermelon, midget muskmelon, Tiny Tim midget peas, dwarf cucumbers, Tom Thumb head lettuce and Morden's dwarf cabbage, to name a few. Suitable also would be Brussels sprouts, which are perfect little replicas of cabbage heads.
STRAIGHT THROUGH THE YEAR
Most of the suggestions offered so far cover summer gardens. No season of the year, however, need be without some plant activity if you plan it that way.
In the early spring the child could have some of the so-called "little bulbs" which produce the first flowers of the season:
Siberian squill (Scilla sibirica)
Spring snowflake (Leucojum vernum)
Winter aconite (Eranthis hyemalis)
Checkered lily (Fritillaria meleagris)
Glory of the snow (Chionodoxa)
Grape hyacinths (Muscari)
and various miniature daffodils. Plant some of these early-birds in breadpans or low pots. Sink these into the ground and cover them with four or five inches of soil for the winter. Then, in late February or early March, transfer them to an outside window-box where the child can watch his brave, bright little garden blooming in the cold blustery days of early spring.
In the autumn a few colchicum bulbs would make a striking introductory autumn project. Placed on a windowsill, these bulbs blossom quite miraculously, without either soil or water.
During the winter it is no trick at all to provide a wide range of gardening divertissements. A Jack-and-the-beanstalk garden is an amusing stunt that the very young gardening prospect will appreciate. Just fill a large flowerpot with soil and firmly anchor in it a three or four foot bamboo stake. Plant a few pole beans close to the stake. A little toy house and a miniature figure (Jack himself) should be placed at the base of the pole. At the top of the pole secure a larger figure, representing the giant.