Potting Mix for Petunias

Petunia Season

• Petunias are annual plants and survive from the last frost in spring to the first frost in fall. Leaves and blooms yellow and die back when temperatures fall under 55 degrees Fahrenheit, so these plants require replanting every spring. Plant annuals in pots to move them indoors to protected locations and grow them year-round or keep them on the porch or patio in the summer season.

Pots and Location

• Petunias need adequate space for both root and foliage growth, and do best with full light and air circulation. Use large 10-gallon pots with drainage holes for multiple petunia plantings and give each plant its cultivar-specific spacing. The University of Minnesota Extension calls light the most important aspect of petunia growth and recommends sites with at least six hours of sun exposure every day for these plants.

Potting Mixes

• Petunias need moderately fertile, quick-draining, moisture-retentive soil. Moisture and drainage become even more important in container situations, as pots dry out more quickly than in-ground plantings. Texas A&M suggests mixing your own potting soil for best results with 1 part peat moss to 2 parts vermiculite or perlite. Purdue University suggests adding garden loam to the mix for better texture. For organic gardening, use 1 part organic compost to 1 part organic garden loam.

Fertilizer and Water

• Give petunias good starting nutrition with 8-8-8 or 5-10-5 fertilizer in their potting soil. The combination of organic matter and fertilizer provides both starting and lasting nutrition for petunias. The Clemson Cooperative Extension recommends watering petunias with at least 1 to 2 inches of water every week to keep them moist. Feed petunias with water-soluble plant food for annuals at every weekly watering to keep them blooming.