Sedum, commonly known as stonecrop, is a genus of resilient, succulent plants popular in landscaping for their fleshy leaves and drought tolerance. These plants store water in their leaves and stems. When other food sources become scarce, the high moisture content of Sedum makes it a target for various animals seeking hydration and sustenance. Understanding the specific culprits and the nature of the damage they inflict is the first step toward effective plant protection.
Mammalian Grazers and Browsers
Deer and rabbits are the most common large mammals that consume Sedum, though they usually prefer other plants when available. These grazers often turn to stonecrop during the winter or periods of drought when their primary forage is less abundant. Deer lack upper incisors and feed by clamping down on a stem and tearing the vegetation, leaving ragged, ripped edges on the remaining stalks. Rabbits use sharp incisors to make a clean, angled cut, often removing entire stems or large sections of foliage close to the ground. Damage typically involves the removal of large plant sections, which can be particularly noticeable on upright varieties like Hylotelephium ‘Autumn Joy’.
Invertebrate Pests and Sap Suckers
Smaller garden pests, including mollusks and insects, cause damage through chewing or extracting plant fluids. Slugs and snails feed on the fleshy leaves, leaving behind large, irregular holes and a characteristic shiny slime trail. Aphids, also known as greenfly or blackfly, are sap-sucking insects that cluster on new growth and the undersides of leaves. They pierce the plant tissue to extract the nutrient-rich sap, which causes leaves to become distorted, curled, or yellowed. Vine weevil larvae are small legless grubs that feed exclusively on the roots of Sedum, often leading to the sudden and complete collapse of an otherwise healthy plant.
Diagnosing the Damage
Identifying the specific pest relies on examining the damage pattern and any residual evidence. Damage from mammals appears as large, missing sections of the plant’s structure. If the remaining stem has a frayed, torn appearance, a deer is the likely culprit, while a clean, sharp, diagonal cut indicates feeding by a rabbit or other rodent. For invertebrate damage, the presence of honeydew, a sticky, sugary substance often accompanied by black, sooty mold, points directly to aphids. Vine weevil larvae damage is characterized by the plant abruptly wilting and dying without any obvious signs of above-ground feeding. This root destruction is sometimes accompanied by half-moon notches along the edges of the leaves, which are the feeding signs of the adult weevils.
Practical Protection Strategies
Mitigating damage requires a targeted approach based on the identified pest type. For mammalian grazers, physical exclusion is the most reliable method, using deer netting or fencing high enough to prevent browsing. Repellents containing ingredients like putrescent egg solids can also be applied to the foliage to deter them with an unpleasant odor or taste.
Managing slugs and snails involves cultural controls, such as reducing mulch and excess moisture around the plants to eliminate their daytime hiding spots. Placing a barrier of copper tape around the base of vulnerable plants or scattering ferrous sulfate pellets provides localized protection. Aphids are controlled with horticultural oil or insecticidal soap sprays, which must be applied directly to the insects, or by introducing natural predators like ladybugs. Treatment for vine weevil larvae is the application of insect-pathogenic nematodes to the soil in late summer or early autumn when the grubs are actively feeding.