Corn Speedwell

Corn Speedwell: A speedy spring weed

If you’ve wondered about the slender, upright weed with tiny purple flowers that’s been abundant this spring, you are not alone! Corn speedwell (Veronica arvensis), a winter annual, is a common landscape and lawn weed that’s also found in fields left fallow. It belongs to the figwort (Scrophulariaceae) family along with other less common weedy speedwells. Seeds germinate in late summer or fall months and sometimes even in early spring. It grows rapidly in spring and completes its life cycle before summer. It has a shallow root system.

Corn Speedwell Identification

Corn speedwell is characterized by oval and pinnate basal leaves with a distinct petiole, arranged oppositely on the stem. The upper leaves are smaller, alternately arranged on the stem and devoid of a petiole. Lower leaves have a round-toothed margin, whereas the upper leaves have fewer serrations with a smooth upper lobe. Both the stem and leaves are hairy. 

There are a few speedwell species that grow in similar habitats around the state. Corn speedwell is often confused with purslane speedwell (Veronica peregrina), which also has opposite basal leaves and alternate upper leaves, however, the leaves of purslane speedwell are hairless. 

Other closely related species are Persian speedwell (Veronica persica) and ivyleaf speedwell (Veronica hederifolia). Both of these speedwells have larger leaves than corn speedwell and are more deeply lobed than the latter. Ivyleaf speedwell has three distinct ivy-shaped lobes. Another closely related species is creeping speedwell (Veronica filiformis), however, this is a perennial weed.

Controls for Corn Speedwell

Corn speedwell has two windows for germination as outlined earlier. Control measures that prevent germination and establishment, such as mulching or application of a pre-emergent herbicide, are effective but should be timed appropriately. To manage established weeds, hand-weeding or light cultivation, such as hoeing, are effective. Once removed, preventative control measures could be put in place. In flowerbeds and landscapes, the herbicide Snapshot (trifluralin and isoxaben) is an effective pre-emergent, broad-spectrum, broadleaf herbicide. Make sure it is applied to established plantings; it can cause injury to new plantings or transplanted plant material. 

In lawns and other types of turf, specialty herbicides, such as Gallery (isoxaben), applied prior to germination or in conjunction with a broad-spectrum, post-emergent herbicide, such as Turflon (triclopyr), Speedzone (a premix of carfentrazone, 2,4-D, mecoprop and dicamba) or Q4 (a premix of quinclorac, sulfentrazone, 2,4-D and dicamba), applied to actively growing plants provide control of speedwells and other broadleaf weeds. Overseeding (in spring and fall), fertilization (in fall and spring) and maintaining a 3-inch mowing height are other cultural practices to maintain a healthy turf to outcompete such pesky weeds.

You also will find these tips useful in addressing other winter annuals such as purple deadnettle, henbit, common chickweed and mousear chickweed. Be sure to read all of the labels carefully before applying an herbicide to ensure that it is safe on the plant material used for and effective for the weed to be controlled. Specialty herbicides, especially certain pre-emergence herbicides, may not be readily available in retail stores. Once you have treated the area, you can reseed the grass to prevent other weeds, such as crabgrass, from establishing in that area.

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