Delphiniums (Larkspur) are popular garden perennials known for their tall, striking spires of blue, purple, and white flowers. Gardeners often wonder if these plants can survive in areas with high deer activity. While no plant is truly immune to a hungry animal, Delphiniums possess natural defenses that classify them as generally deer-resistant. This means they are not a preferred food source, though they are not guaranteed against all browsing.
Palatability and Toxicity
The primary reason deer avoid Delphiniums is the presence of potent chemical compounds found throughout the plant. These compounds are highly toxic substances known as diterpenoid alkaloids. One of the most studied is methyllycaconitine, which acts as a powerful neuromuscular blocking agent in mammals.
If a deer consumes a sufficient quantity, these alkaloids can lead to severe sickness or death by respiratory failure. The bitter taste acts as a strong deterrent, causing deer to instinctively browse elsewhere after a single nibble. Consequently, Delphiniums are placed in the “deer-resistant” category, acknowledging their natural defense mechanisms.
Situations Where Browsing Still Occurs
Despite their toxicity, Delphiniums can still be browsed under certain environmental conditions. The difference between a deer-resistant and a deer-proof plant is clear when food scarcity is a factor. When deer are under extreme pressure, such as during severe drought or deep winter snow, they will consume nearly any vegetation to survive, overriding their natural avoidance of toxins.
The plant’s toxicity can fluctuate throughout the growing season. The highest concentration of toxic alkaloids is often found in early spring growth, declining significantly after the plant has flowered. Young, tender new growth may also be more appealing or less concentrated with toxins, making it a target for opportunistic browsing. High population density also increases competition, forcing deer to be less selective about forage choices.
Effective Deterrence Strategies
Gardeners in areas with active deer populations should implement preventative measures. The most reliable physical barrier is a permanent fence, which must be at least seven feet high to prevent deer from jumping. A solid structure, like a six-foot stockade fence, is also effective because deer are reluctant to jump over barriers they cannot see through.
Chemical repellents offer a practical intervention for smaller areas by introducing an offensive taste or smell to the foliage. Repellents often contain active ingredients like putrescent egg solids or dried blood, which signal danger or decay to deer. These products require regular reapplication, especially after heavy rain, to maintain efficacy. To prevent deer from becoming accustomed to one repellent, it is effective to rotate between two or more different types throughout the season.