Peter H. Dernoeden, Ph. D.

How to Identify Slender Speedwell and Corn Speedwell

Slender speedwell (Veronica filiformis), also known as creeping speedwell or creeping veronica, is a perennial that produces an abundance of light blue flowers in late winter and early spring. It grows in sun and shade, but is most dominant in open and sunny locations.

Corn speedwell (Veronica arvensis) is a winter annual that has similar vegetative characteristics, but has much smaller leaves and less conspicuous flowers than slender speedwell. Corn speedwell inhabits sunny and shaded lawns. Dense patches of corn speedwell develop in thin or open turfs.

They are especially adapted to growing in compacted soils, slopes, hot and wet areas such as swales, and along sidewalks and adjacent to buildings.

Characteristics and Emergence of Slender Speedwell

Slender speedwell is a perennial that emerges in the autumn from overwintering stems called stolons or from seed. Slender speedwell does not become conspicuous until late winter, when an abundance of light-blue flowers appear. Leaves are small, and rounded or heart-shaped.

By mid-spring, slender speedwell produces creeping stems (i.e., stolons) with hairs that root at nodes. Mature clusters of plants are low growing and stolon growth can result in the development of dense mats of plants (that can be difficult to remove with a pocket knife), which enables slender speedwell to out-compete turf. Solitary plants grow upright in turfs that have not been mowed since the previous autumn.

There can be several variations, but generally flowers have four blue or violet and sometimes one white petal.

Flowers appear in abundance, especially in sunny areas from late winter and throughout early spring. Flowers (≈ 0.4” diameter) form in leaf axils on long (≈0.5” or longer) stalks. Flowers eventually develop into small inconspicuous, heart-shaped and fuzzy seed capsules. With the onset of warmer temperatures in early summer leaves senesce and die, but plants survive as stolons and seed until autumn.

Defining Traits of Corn Speedwell

Corn speedwell is a winter annual (i.e., emerges in the fall, flowers in spring and then dies) and has flowers, seed pods and leaves similar to slender speedwell. Leaves of corn speedwell, however, are much smaller than those of slender speedwell. Upper leaves are very small and appear in clusters.

Larger lower leaves initially are oblong, but as they mature they become heart-shaped with notched lobes. Flowers of corn speedwell are less showy, but are conspicuous from a standing position. Flowers have four petals that are light blue or violet (≈ 0.2” in diameter) and form on very short (< 0.1”) stalks.

Plants have branched stems that radiate from the base that trail, but do not root at nodes. Corn speedwell senesces and dies with the advent of high temperatures in summer, and survives as seed.

Corn speedwell is differentiated from slender speedwell based on smaller leaf size, smaller flower diameter and shorter flower stalks.

Also, slender speedwell normally produces flowers a few weeks in advance of corn speedwell.

Treatment and Applications for Speedwell

Herbicides are not needed where speedwells are isolated, since they senesce by early summer.

In open and immature stands, however, they can be competitive and an herbicide application may be warranted.  Unfortunately, speedwells are notoriously difficult to control.

Two or 3 way combinations of 2,4-D, MCPP, dicamba, clopyralid (not for lawns), fluoxypyr, or triclopyr are commonly used.

Mixing a combination product with carfentrazone (i.e., Quicksilver) such as Speedzone improves control in cooler weather.