Weed of the Month (June 2009): Scarlet Pimpernel

Photos by MG Laura Bellmore

By Marian Kimbrough MG 2007

ne man’s weed is another man’s treasured Oplant…so it is with Scarlet Pimpernel (Anagallis arvensis). Here in the Galveston-Hous- ton area this vascular plant is considered a weed; cientific however, it is not invasive. Its strikingly beautiful S flowers notwithstanding, Scarlet Pimpernel has Name been a common weed pest in our MG Demonstra- Anagallis arvensis tion Garden in Carbide Park. It sometimes can be mistaken for chickweed, but is easily identified by Fig. 1 its singly pink flower of 5 small petals (Fig. 1) oc- Other curring at leaf axils along the stem. Common Plants can grow 12+ inches tall (Fig. 2). Leaves ames occur in pairs along a square stem and are bright N green with purple spots on the lower leaf surface Scarlet Pimpernel, (Fig. 3), and the pink bloom at the top. The Shepherd’s Barometer, growth pattern of the stem may be along the Poor Man’s Weath- ground or at an angle to it, either way the leaves al- erglass, Adder’s Eyes, ways face up to the direction of the source of light. Bipinella The petals are very light sensitive, not open- ing until around nine o’clock in the morning and usually closing no later than four o’clock in the afternoon. Many of the common names that Fig. 2 Scarlet Pimpernel is known by were given due to the weed’s reaction to changes in weather, such as the sky becoming overcast, or rain pending. This weed is usually found along roadsides, near crop fields, and in waste places where conditions are very dry. Propagation of Scarlet Pimpernel is en- tirely by seeds. The plant is an annual and will die back completely, including the root system, at the end of each growing season. The blooming season of Scarlet Pimpernel in this area can be from late March all the way through October. The fruit in the center of each pollinated flower swells and Fig. 3 ripens to form a little capsule (Fig. 4). Seeds can remain viable up to ten years. Management of this weed in landscape beds is best accomplished by a normal tilling/hoeing routine. Pre-emergent herbicides such as those in “weed and feed” products for broadleaf weeds may be used to prevent seed germination in lawns; however, the timing of application is crucial. In our growing area, early October would probably be the best time to apply a pre-emergent. This plant was not native to the United States but was introduced from other countries where it Fig. 4 was often considered a desirable plant (their “trea- sure”). In days of old, Scarlet Pimpernel was used for medicinal purposes.