Petunias are half hardy annuals and are related to the potato and other members of the nightshade family. Their familiar trumpet shaped flowers come in several shapes. Moreover sizes and colors, from the old fashioned single flowers to modern hybrids that are striped, double ruffled and sometimes very large at least four inches across for the grandifloras. The new multiflora petunias are small and single and bloom very profusely they are also disease resistant. Since petunias make compact plants with masses of color, they are excellent in flower borders. We find that more modest, simpler petunias are less decimated by heavy rainstorms than the more flamboyant ones; the latter, though are fine as container plants in sheltered locations. The trailing petunias, such as the grandifloras, are especially effective in pots, planters and boxes. Petunia colors are virtually unlimited; there are even striped, bicolored ones. Height ranges from six inches dwarfs to 18 inches full size plants.
How to Grow Petunia
Well, you need to sow seeds indoors eight to ten weeks before the last frost, dropping the tiny seeds onto the soil surface and pressing lightly with the fingers. Keep the seedlings cool, and transplant then carefully to individual peat pots when each seedling has four leaves. They can be set out in the garden 12 to 18 inches apart after danger of frost in fairly fertile soil. Some petunias especially the doubles are slow to grow from seed and you may be better off with nursery grown seedlings.
Petunias are warm weather plants but they sometimes do poorly during hot weather. If they look straggly and aren’t blooming well, cut them back to a few inches tall and feed them liquid fertilizer that you water in well. Petunias will self-sow readily, but the seedlings will rarely look anything like the parents.