The perennial known as the Obedient Plant (Physostegia virginiana) is a popular choice for native gardens and perennial borders across North America. This plant is easily recognized by its rigid, upright habit and unique four-sided, or square, stems. Its common name comes from the characteristic that its individual tubular flowers, which bloom on terminal spikes, will temporarily hold any position they are nudged into. This article examines the Obedient Plant’s defense mechanisms and its classification regarding deer resistance.
Classification of Obedient Plant as Deer Resistant
The Obedient Plant is widely classified by horticultural experts and university extension programs as deer resistant. This designation means the species is generally considered unpalatable to deer and is low on their preference list of available forage. In landscapes with moderate deer activity, the plant is rarely browsed, making it a reliable option for gardens.
This resistance is a significant factor in its popularity, as it offers a perennial with showy summer and fall flowers that typically remain untouched. While not immune to being sampled, it is not a preferred food source, placing it among plants deer tend to pass over in favor of more desirable vegetation.
Plant Characteristics That Deter Deer
The plant’s inherent resistance is due to a combination of physical and chemical characteristics that make it undesirable for grazing. As a member of the Lamiaceae family (which includes mints), the Obedient Plant possesses vegetative parts containing aromatic compounds. These oils provide a strong, distasteful scent when the plant tissue is crushed, a factor deer are highly sensitive to.
Physically, the plant presents a deterrent through its structure, specifically its sturdy, square stems. These rigid, unbranched stems are less tender and more difficult for deer to tear or chew than the succulent stems of other herbaceous plants. The lance-shaped leaves also have a slightly rough, tough texture that is not appealing to a deer’s palate.
Situations Where Browsing Still Occurs
No plant is entirely deer-proof, and the Obedient Plant’s resistance can be overcome by environmental factors. Under conditions of extreme deer pressure, where local populations are high and alternative food sources are scarce, deer will broaden their diet to include less palatable plants. This forced browsing can lead to damage on plants that are normally avoided.
Severe weather conditions can also override the plant’s natural defenses, particularly during prolonged drought or harsh winter. When preferred forage is unavailable, a hungry deer may resort to eating almost any available green material. Immature or new spring growth is especially vulnerable, as the young shoots have not yet developed the full concentration of deterrent oils or the stiffness of mature stems.