What Do You Put on Petunias?

Soil Preparation

• Petunias grow best in moderately rich, well-drained soil in full sun, which is six hours or more of direct sunlight each day. To prepare the soil for planting petunias, spread 2 to 3 inches of well-rotted compost over the planting area, along with a balanced fertilizer with the fertilizer ratio of 10-10-10, 8-8-8 or 13-13-13. Use the amount of fertilizer recommended on the label for new flower beds. Work the compost and fertilizer into the top 8 inches of soil with a shovel or garden fork.

  Although petunias can be grown from seed, the easiest way to obtain petunias is from your local nursery. They are one of the first bedding plants to arrive in spring. Choose healthy strong plants with no yellowed, wilted or spotted leaves.

  Plant in the garden after all danger of frost has passed. If possible, plant on a cloudy cool day to prevent transplant shock. Pinch off existing blooms to encourage branching. Water the soil around the plants after planting to settle the soil and prevent air pockets. A 1 to 2 inch layer of mulch around the plants keeps the soil moist and controls weeds.

Watering

• Petunias need frequent watering to prevent wilting. Large-flowering types of petunias, such as spreading petunias and grandifloras, may never recover if they are allowed to completely wilt. Keep the soil moist, but not wet. Over-watering petunias invites mildew and fungal diseases. Water plants by gently watering around the root system. Do not allow the foliage or flowers to get wet when watering.

Fertilizing

• Fertilize petunias in the garden every two weeks with a water-soluble fertilizer. If the petunias are in a container, fertilize once a week with a water-soluble fertilizer diluted to half-strength. Do not over-fertilize. Adding too much fertilizer creates excessive green growth at the expense of bloom production.

Pest Control

• Petunias are a relatively pest-free plant. If slugs and snails are a problem, use a snail and slug bait for control or pick them off by hand. Snails and slugs are most active at night. Control worms and caterpillars that feed on the leaves and flowers with regular application of Bacillus thuringiensis (Bt) or spinosad. Both Bt and spinosad are organic pesticides made from naturally occurring ingredients. For flea beetles or other pests, dust with pyrethrum powder, which is also an organic solution. Use all pesticides as directed on the label. Usage amounts will vary according to the number of plants and concentration of the pesticide.