Deer generally avoid consuming green onions, also known as scallions, a common concern for home gardeners. These browsing animals can quickly decimate a garden, forcing many to choose naturally less appealing plants. Green onions are immature onions harvested before the bulb swells. Their strong chemical defenses, rather than just deer preference, determine their resistance.
The Palatability Question
Deer generally do not eat green onions, which are widely categorized as highly deer-resistant plants. The strong, sharp flavor and intense odor of the foliage make them one of the last choices for a foraging animal. This natural aversion means green onions can often be planted without additional physical protection.
Deer rely heavily on their sense of smell to identify palatable food sources and avoid harmful plants. Green onions fail this test immediately due to their strong scent, signaling an unpleasant meal. However, no plant is entirely “deer-proof.”
In rare situations, such as extreme drought or high population density where preferred forage is scarce, deer may consume repellent plants. A starving animal’s priority shifts from preference to survival, leading it to browse undesirable vegetation. For the most part, green onions remain safely off the menu.
Chemical Compounds Driving Avoidance
The mechanism behind this avoidance is rooted in the green onion’s unique biochemistry. Green onions belong to the Allium genus, which includes garlic, chives, and common bulb onions. All plants in this family contain specialized sulfur compounds that cause their characteristic, pungent aroma and taste.
When the leaf tissue is damaged, an enzyme called alliinase is released. This enzyme instantly converts non-volatile sulfur-containing molecules into highly volatile, odoriferous compounds called thiosulfinates.
These thiosulfinates are intensely disagreeable to a deer’s sensitive palate and nasal passages. The strong smell acts as an immediate deterrent, while the sharp, acrid taste confirms the plant is not a desirable food source. This potent chemical defense system provides natural self-protection against herbivores.
Protecting Your Plants From Deer
Gardeners can leverage the green onion’s natural properties to protect more vulnerable crops. A practical strategy is using green onions and other Allium species as companion plants. They can be established as a protective perimeter around palatable vegetables like lettuce or beans. The strong scent barrier created by the onions can mask the attractive smells of neighboring plants, causing deer to bypass the area.
For maximum protection, a physical barrier is often the most reliable method. Since deer are excellent jumpers, a single fence must be at least 7.5 feet high to be effective. A less intrusive alternative is a double-fence system, which uses two parallel, shorter fences spaced three to five feet apart.
Another effective approach is the use of contact repellents applied directly to the plant foliage. These products fall into two categories: taste deterrents and scent deterrents.
Scent-based repellents often use putrescent whole egg solids, which emit a sulfurous odor mimicking a predator’s smell. This odor triggers an instinctive fear response in the deer. Taste-based deterrents frequently contain capsaicin, the active compound in chili peppers. When a deer samples a treated plant, the capsaicin causes an immediate burning sensation. This negative experience encourages a learned aversion, preventing future browsing.