Lobelia is generally considered deer resistant, making it a popular choice for gardeners in areas with high browsing pressure. This large genus includes both annuals, like the popular trailing varieties (Lobelia erinus), and robust perennials, such as Cardinal Flower (Lobelia cardinalis) and Great Blue Lobelia (Lobelia siphilitica). Deer avoidance is not due to physical features like thorns, but primarily to chemical compounds within the plant tissues. Lobelia is far down on a deer’s list of preferred food sources.
The Mechanisms Behind Lobelia’s Deer Resistance
The reason deer tend to bypass Lobelia lies in its biochemistry, specifically its production of defensive compounds called alkaloids. These naturally occurring organic compounds have pronounced physiological effects on animals. Lobelia species contain several pyridine alkaloids, with the most well-known being lobeline.
Lobeline and its related compounds are toxic when ingested and have a highly unpalatable, bitter flavor that discourages deer from consuming the plant material. The bitter taste serves as an immediate deterrent, causing the deer to spit out the plant after a single bite. If large quantities were consumed, these compounds can cause significant digestive upset and even poisoning, which deer instinctively avoid.
The deer’s strong sense of smell also plays a role in their avoidance of Lobelia, as the plant possesses a noticeable, tobacco-like scent that is generally off-putting to them. This combination of offensive odor and bitter, toxic chemical content makes Lobelia a highly effective natural defense against browsing. It is a poor food choice compared to other available forage.
Variances in Resistance Across Lobelia Species
While the entire genus is generally deer resistant, the level of protection can vary slightly between different species. Perennial varieties like the striking red Cardinal Flower (L. cardinalis) and the blue-flowered Great Blue Lobelia (L. siphilitica) are highly reliable and consistently avoided by deer. These native perennial types often contain a higher concentration of the protective alkaloids, making them especially unappealing.
Some of the smaller, annual basket varieties, such as Lobelia erinus, are also considered resistant, though their delicate nature might make them a less absolute deterrent. When preferred food is scarce, such as during severe drought, harsh winter conditions, or in areas with a high deer population, a starving deer may sample or consume plants they would normally ignore.
Gardeners should consider the local deer population’s desperation level and the plant’s variety when assessing the likelihood of damage. While the plant’s chemical defenses are strong, they cannot always guarantee protection under conditions of severe food scarcity.
Mitigation Strategies When Deer Pressure is High
If you are gardening in an area where deer pressure is consistently high, relying solely on Lobelia’s natural resistance may not be enough. Strategic planting is highly effective, involving placing Lobelia near plants deer find offensive, such as strongly scented herbs like lavender or sage. Creating a perimeter of fragrant plants helps deter deer from entering the area.
Physical barriers offer the most reliable protection, particularly for young or newly planted Lobelia that are more vulnerable. Temporary netting or low fencing can be used to protect specific beds, as deer are often hesitant to jump over barriers when they cannot clearly see a safe landing spot on the other side. For a non-permanent solution, motion-activated sprinklers can startle deer, training them to avoid the area without causing any harm.
Commercial or homemade repellents can also be used as a secondary line of defense to bolster the plant’s natural unpalatability. Repellents typically use foul odors or tastes, such as dried blood or capsaicin, to discourage browsing. These sprays must be applied regularly, especially after heavy rainfall or new growth, to maintain their effectiveness and teach the deer to seek food elsewhere.