Petunias are widely planted flowering annuals, known for their bright colors, trumpet-shaped blooms, and pleasant fragrance. Their popularity and physical characteristics make them a frequent target for various garden inhabitants seeking a quick meal. Tender foliage provides moisture, and the flowers contain nectar, which offers a high-energy reward. These desirable qualities mean petunias are regularly browsed by a range of animals and smaller pests.
Common Mammals That Eat Petunias
Significant, overnight damage to petunias is typically caused by larger herbivores, most commonly deer and rabbits. These mammals are opportunistic foragers that find the soft, succulent nature of petunia leaves and stems highly palatable. The physical evidence left behind by these two groups differs significantly based on their dental anatomy and foraging height.
Rabbits are low-level feeders that prefer young growth and stems close to the ground, rarely feeding higher than two feet. Their sharp incisors result in a clean, neat cut across the stem, often at a 45-degree angle. Deer are browsers that lack upper incisors, instead possessing a hard dental pad. When they pull at a petunia, they tear the plant tissue, leaving behind ragged, uneven edges on the remaining stems and foliage. Woodchucks (groundhogs) also consume petunias, often focusing on the flowers and tender buds.
Invertebrates and Smaller Pests
When damage is localized or appears as small holes rather than large sections missing, the culprits are usually smaller invertebrates. Slugs and snails are notorious nocturnal feeders that graze on the tender leaves and flowers of petunias. Their feeding leaves behind irregular, ragged holes in the foliage, and their presence is confirmed by a distinctive silvery, dried mucous trail left on the plant or surrounding soil.
The Tobacco Budworm, the larval stage of a moth, is a destructive pest for petunias. These caterpillars often burrow into the flower buds, causing them to fail to open or resulting in tattered blooms. As they feed, they leave behind small, dark, pepper-like droppings, known as frass, which indicates their activity. Other sap-sucking insects, primarily aphids, cluster densely on new growth and the undersides of leaves. These pests extract plant juices, leading to yellowing, curling leaves, stunted growth, and often excreting a sticky substance called honeydew.
Analyzing Damage Patterns
Identifying the specific animal responsible requires a careful examination of the remaining plant material and the surrounding environment. If entire stems are clipped cleanly near the base, especially below two feet, the most likely source is a rabbit. Conversely, if the damage is higher up and the remaining plant parts show torn, shredded ends, the feeding is likely the result of deer browsing.
Smaller-scale damage involving holes in the leaves and flowers points toward invertebrate pests. The presence of a shiny, dried slime trail confirms the activity of slugs or snails, which feed primarily at night or on damp days. If the flower buds themselves are damaged, failing to open or showing small entry holes with dark, grit-like droppings nearby, the Tobacco Budworm is the responsible party. Finally, if the foliage is sticky, yellowing, or covered in black sooty mold, a dense colony of aphids or other sap-suckers is the cause.
Strategies for Protecting Petunias
Protecting petunias is best accomplished through targeted measures based on the identified pest. For rabbits, low-profile wire mesh fencing, at least two feet high, installed to surround the planting and secured at ground level, is effective. Deer require much taller fencing, typically eight feet high, but can also be deterred by taste- and scent-based commercial repellents that must be reapplied after rain or new growth.
Controlling slugs and snails involves reducing the moist, dark habitat they prefer by clearing away leaf debris and avoiding overhead watering late in the day. Targeted molluscicide baits containing iron phosphate can be sprinkled around plants. For the Tobacco Budworm, diligent hand-picking of the caterpillars and affected buds is effective in small gardens. An application of a microbial insecticide containing Bacillus thuringiensis (Bt) can target younger, actively feeding larvae. Aphids can be managed by spraying the affected areas with a strong jet of water to dislodge them or by applying insecticidal soap.