The Speedwells are low plants with small 4-lobed flowers in leafy racemes. One flower lobe is smaller than the others. Thyme-leaf Speedwell is a creeping perennial forb with slender decumbent stems that are green and covered with fine hair although some plants may lack hair.
The leaves are opposite, ovate to ovate-oblong in shape, from 1/3 to an inch long, 1.5 to 2.5 x as long as wide, with very short stalks on the lower leaves and stalkless upper leaves. The margins vary by plant from entire to coarsely scalloped. The very upper leaves change from opposite to alternate. There are 3 to 5 veins rising from the base of the leaf. Leaf tips are obtuse to rounded.
The inflorescence is a terminal raceme that rises erect from the decumbent stem. The stem usually has fine hair, sometimes glandular. Oblong green leafy bracts subtend the flower.
The flowers are stalked with a bell-shaped corolla that has 4 white to bluish-white rounded lobes which spread outward. The upper and two lateral lobes are streaked with purple veins while the lower lobe is not and is smaller and narrower than the other 3 lobes. The outer green calyx is small but with 4 large lobes (sepals), narrower than the petals but just as long. The reproductive parts included 2 stamens with white filaments and blue-purple anthers; a single style with a knobby tip attached to a greenish 2-locular ovary. Both stamens and style are exserted from the corolla. At the base of the flower stalk is an ovate bract similar in shape to a leaf, and longer than the flower stalk.
Fruit: Flowers mature to a seed capsule, broader than tall, that contains 50+ small ellipsoid shaped flat dry seeds.
Varieties: See notes below.
Habitat: Thyme-leaf Speedwell grows in fields and thickets where there is adequate soil and moisture and generally full sun for flowering. The non-native variety (shown here) is generally found in lawns emerging above grass level when the flowering stem rises. It grows from a rhizomatous root system of long slender rhizomes which allow the plant to from dense matted colonies.
Names: The genus Veronica was supposedly named after St. Veronica. The species, serpyllifolia, means 'with leaves like' the plant Thymus serpyllum. The author name for the plant classification, 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. In recent years botanists have reclassified all the Veronica genus from the Figwort family into the Plantain family. Many references will still list the older classification.
Varieties: Two are have been recognized in North America: Var. humifusa, which is considered a native plant with bright blue flowers and var. serpyllifolia, which is an invasive import from Europe that has flowers as described above. However in the recent publication (2019) of Volume 17 of Flora of North America it is the considered opinion that there is so much intergradation that there may be little reason for the separation.
Above: Thyme-leaf Speedwell grows from a low stem with just the flowering section rising. When in a lawn as seen here just the flowers of the raceme extend above grass level.
Below: The flowers are subtended by a leafy bract that is longer than the flower stalk. Stems can be hairy as seen here. The lobes of the calyx are as long as the corolla lobes. Speedwells have one petal of the corolla smaller than the others.
Below: The ovate leaves are almost stalkless. The root is composed of slender rhizomes.
Eloise Butler first introduced Thyme-leaf Speedwell to the Wildflower Garden in 1913 with plants imported from Kelsey's Nursery in North Carolina. It is unclear which variety she brought in. Martha Crone planted it in 1935, but they were no longer extant at the time of Martha Crone's 1951 census.
Both varieties of the plant are found in Minnesota. The DNR does not track them by county. In North America, the native var. humifusa, is found in from the Rocky Mountains westward, then a gap until the population begins again in Minnesota and Ontario, spreading eastward to the coast, but not south of MN, WI, MI and NY. The non-native variety, var. serpyllifolia, is found mostly in the eastern half of the continent with some known in the Northwest from Washington and Oregon and up the coast of British Columbia to Alaska. As noted above the photos in the "varieties" section it is recent opinion that there should not be a separation into varieties.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"