For small containers or the edging of boxes and planters, choose the miniatures-the rosy Bright Eyes with a white throat, rose-starred white Twinkles, light Silvery Blue, and white Igloo. For hanging baskets, window boxes, shelves, and wall brackets, there is nothing prettier than the balcony types with their cascading habit. In this group are the mahogany Black Prince, deep Royal Blue, and clear Royal Rose.
Try petunias, too, in pots and tubs, boxes and movable planters. Window boxes and small planters on driveways, walks, terraces and porches offer excellent settings for their summer cheer. Since they are easy to raise from seed and inexpensive to buy as seedlings, keep extra petunias on hand to replace other plants that pass their prime in the planters attached to the house. Petunias are ideal for window boxes with emphasis on one variety. Alone the frilled rose-pink Prima Donna or the red Co-manche will give a striking effect.
Petunias combine well with geraniums, heliotropes, lobelias, sweet alyssum, dwarf marigolds, patient Lucy, coleus, vinca, and German ivy. Some gardeners dislike petunias with the distracting foliage of coleus, but plain white petunias with red- or pink-leaved coleus make a pleasing picture. In front of evergreens, the colors of petunias seem more intense, a good reason for using them with yews, junipers, boxwood, and hollies in large planters.
In containers petunias can be planted six to eight inches apart, closer than in the garden. For their more confined roots, the soil mixture should be well prepared, with bonemeal or superphosphate added. If soil is heavy, lighten it with sand or peatmoss. This will also make it porous. When feeding during the growing season, use a high phosphorous combination-5-10-5 or 2-6-2. Plants will need sun for several hours a day if you expect bountiful results.
When plants are a few inches high, pinch out tips to encourage branching, and as they grow keep pinching to keep plants compact. If you snip the first blossom, the plants will flower more profusely. Remove faded blooms each day or at least twice a week to improve the plant's appearance and prevent seed formation.
Water petunias when they need it, usually when the surface of the soil looks dry. Allowed to dry out completely, plants will wither, yet with too much water they may rot. Apply fertilizer, preferably in liquid form, every three to four weeks, one teaspoon of a balanced type to one gallon of water.
Heavy rains will spoil blooms. If possible, move containers to shelter. Avoid watering plants with sprinkler or hose, for water spots petals, particularly the dark purple varieties. New blooms, however, replace the old in a day or two of clear weather.