Delphinium, also known as Larkspur, is a genus of flowering plants prized for its tall, stately spikes of blue, purple, pink, or white flowers. These striking perennials are common in cottage gardens and formal borders. For many homeowners, the presence of deer creates a conflict between cultivating these plants and protecting them from browsing damage.
The Straight Answer on Delphinium and Deer
Delphinium plants are widely recognized as highly deer-resistant, meaning they are seldom chosen as a food source. The plant’s inclusion on lists of avoided species indicates its general unpalatability. This resistance significantly reduces the likelihood of damage compared to highly palatable plants like hostas or tulips. Deer prefer nutritious and easy-to-digest vegetation, making them inclined to bypass Delphinium.
The tough, slightly fuzzy texture of the leaves adds to the plant’s lack of appeal. Most browsing animals sample a plant before eating a large quantity, and the taste of Delphinium quickly signals it is not desirable food. While a deer might take an exploratory bite, it usually moves quickly to find a more appetizing option.
Understanding Delphinium Toxicity
The primary reason deer avoid Delphinium is the presence of potent chemical compounds found throughout the plant structure. These compounds are a class of poisonous substances known as diterpenoid alkaloids, such as delphinine and methyllycaconitine (MLA), which act as natural anti-herbivory defenses.
When ingested, these alkaloids interfere with the nervous system, acting as antagonists at nicotinic acetylcholine receptors. This disruption can lead to symptoms ranging from severe gastrointestinal distress to neuromuscular paralysis. In large quantities, these toxins cause cardiotoxic effects, including hypotension and arrhythmias, which can ultimately lead to respiratory failure. The highest concentrations of these toxic substances are often found in the younger shoots and the seeds.
When Deer Ignore Their Natural Preferences
While Delphinium is generally avoided, deer may browse plants they normally ignore under extreme environmental stress, known as starvation browsing. When preferred food sources become scarce, such as during severe winter weather or prolonged drought, deer may consume toxic or unpalatable plants out of desperation.
High population density also increases the risk of damage, as competition for food drives deer to accept less palatable options. In these situations, the deer’s natural aversion to the alkaloid content is overridden by the immediate need for caloric intake. Young deer, or fawns, sometimes sample plants indiscriminately as they learn what is safe.
Practical Strategies for Garden Protection
For gardeners aiming to ensure their Delphinium remains untouched, proactive measures can supplement the plant’s natural defenses. Installing physical barriers offers the most reliable protection against deer browsing. Fencing must be at least eight feet high to deter jumping, or a double-layer fence with a gap can confuse their depth perception.
Cultural controls, such as planting Delphinium near highly repellent species, can also be effective. Placing plants close to fragrant herbs like lavender, rosemary, or mint may help mask the Delphinium’s scent and discourage investigation. Applying commercially available scent or taste deterrents is beneficial, though these require reapplication, especially after rain. Motion-activated sprinkler systems or ultrasonic devices offer another layer of protection by startling deer that venture too close.