Alstroemeria, often known as the Peruvian Lily, is a popular garden perennial celebrated for its long-lasting, vibrant blooms. Gardeners frequently seek flowers that can withstand browsing, and Alstroemeria is widely regarded as deer resistant. Deer typically avoid eating its foliage and stems due to natural chemical defenses the plant has evolved. Choosing plants like the Peruvian Lily can reduce the risk of damage in areas with high deer populations.
The Chemical Reason Deer Avoid Alstroemeria
The primary reason deer bypass the Peruvian Lily is the presence of defensive chemical compounds within the plant tissue. These deterrents are concentrated in the foliage and stems, making the entire plant unpalatable. The most notable of these compounds is tulipalin A, a naturally occurring toxin. Tulipalin A acts as a feeding deterrent by causing irritation. When a deer samples the plant, this compound causes an unpleasant reaction, discouraging further consumption. This chemical is also known to cause contact dermatitis in humans, highlighting its irritating properties.
The plant also contains its precursor, tuliposide A, which contributes to the defensive mechanism. By producing these irritants, the resulting bad taste and potential for digestive upset mean that deer instinctively learn to avoid the plant after a single exploratory bite.
When Resistance Fails Understanding Deer Pressure
While Alstroemeria possesses strong defenses, the term “deer resistant” is distinct from “deer proof.” Resistance can fail under specific environmental conditions known as high deer pressure. This pressure refers to the intensity of feeding behavior driven by a lack of alternative food sources. When conditions are harsh, such as during a severe drought or deep winter, a starving deer will disregard its normal preferences. In these desperate situations, the mild toxicity or unpalatability of Alstroemeria becomes an acceptable risk for survival. High deer populations also contribute to this pressure, forcing animals to sample plants they would typically ignore.
Young, inexperienced deer are also more likely to browse resistant plants as they learn which species to avoid. The tender, new spring growth of Alstroemeria may also be sampled because it is softer than the mature foliage. Therefore, a plant’s resistance is always relative to the available food in the surrounding environment.
Supplemental Deterrence Strategies
Gardeners facing persistent deer damage should implement external measures to supplement the plant’s natural resistance. The most dependable solution is installing physical barriers to prevent access entirely. For effective deterrence, a permanent fence should be at least eight feet tall, as deer easily clear lower obstructions. In smaller or more suburban gardens, a seven-foot fence may suffice because wooded areas and obstacles make deer hesitant to jump without a clear landing zone.
Alternatively, taste and scent-based repellents can be applied directly to the plants, relying on foul odors or bitter flavors to discourage browsing. Repellents require diligence for sustained effectiveness, necessitating reapplication approximately every three to four weeks. Heavy rainfall or overhead watering can wash away the active ingredients, requiring an immediate re-spray to maintain the barrier.