Petunias are bright and colorful annual flowers thriving throughout the country. They grow in both small and large varieties and bring color to all summertime gardens. They require the right season and conditions to maintain healthy stems, foliage and blooms. Petunias may go brown for a number of reasons.
Petunias are annuals, and so grow for only one season. They require midspring plantings and summer growing seasons. Do not plant them outdoors until all frost is past. These plants grow well in gardens, pots and hanging containers.
Annual flowers die in frost, so petunia leaves naturally yellow and fade when fall approaches. Browning in fall simply means that the petunias are at the end of their lifespans. Save petunias in pots by moving them indoors and out of the frost.
According to the University of Minnesota, light is the most important aspect of petunia growing. Petunias that don't receive at least five to six hours of full sun every day won't bloom or spread. Heavily shaded petunias may display yellow or brown leaves from lack of sun.
Soil and Spacing
Petunias require moderately fertile, quick-draining soil and will rot and die in tight soil or standing water. The University of Minnesota recommends amending soil with peat moss or compost before planting. Give petunias 8-8-8, 10-10-10 or 12-12-12 fertilizer at planting to increase growth and blooming.
Petunias that don't get enough water will die with wasted blooms and brown, crumbling leaves. Increase watering to 2 to 3 inches of water a week to save brown and dying petunias.