The plant genus Veronica, commonly referred to as Speedwell, contains hundreds of species, making the question of its invasiveness complex. While some Speedwells are beneficial native plants or desired garden ornamentals, others are aggressive weeds that can overrun turf and cultivated areas. Identifying a single plant as “Speedwell” is not enough; a closer look at the specific species is necessary to understand its potential to be problematic. The genus is diverse, exhibiting a wide range of growth habits, from low-growing annuals to upright perennials.
Speedwell’s Dual Identity: Native Ornamentals vs. Weeds
The confusion surrounding Speedwell stems from the stark differences within the genus. Many species, such as the tall, spiky Veronica spicata, are prized by gardeners for their dense, upright flower clusters in shades of blue, pink, or white. These ornamental varieties are generally well-behaved and provide color and structure to garden beds. North America also hosts native species that serve as beneficial groundcovers or wildflowers, contributing to local ecosystems.
Conversely, a number of Speedwell species introduced from Europe and Asia have naturalized in North America and become notorious agricultural and lawn weeds. These non-native types thrive in disturbed soils, competing vigorously with desired plants for water, nutrients, and sunlight. Their aggressive nature has made “Speedwell” synonymous with a persistent garden pest for many homeowners and farmers. The designation of a Veronica as a problem plant depends entirely on its origin and its specific growth characteristics.
Identifying the Most Common Invasive Species
Three non-native species are particularly recognized for their weedy behavior in lawns and gardens.
Persian Speedwell (Veronica persica)
This is a sprawling winter annual characterized by relatively large, bright blue flowers (8 to 13 millimeters wide) with white centers. Its leaves are oval to heart-shaped with serrated margins, arranged alternately on the upper stems. This species is commonly found in gardens and turfgrass, where it produces a sprawling, low-growing mat of hairy stems.
Corn Speedwell (Veronica arvensis)
This common winter annual weed is distinguishable by its more upright, low-growing habit, typically reaching heights of about 6 inches. Its flowers are much smaller and less conspicuous than the Persian variety, usually pale blue or white and only 2 to 4 millimeters wide, nestled in the leaf axils. The lower leaves are opposite and have rounded teeth, while the upper leaves are smaller and lack stalks.
Creeping Speedwell (Veronica filiformis)
This perennial is one of the most prominent weeds in home turf. Originating in eastern Europe and western Asia, it forms dense mats through slender, trailing stems that root readily at the nodes, allowing rapid spread across lawns. Its small leaves are round or kidney-shaped with notched edges, and its flowers are solitary, light blue, and borne on long, thin stalks. This aggressive mat-forming habit suppresses turfgrass, creating bare patches.
Mechanisms of Spread and Establishment
The success of weedy Speedwells is rooted in their efficient reproductive strategies, allowing them to establish and persist under various conditions. Annual species like Persian and Corn Speedwell rely heavily on prolific seed production to colonize new areas. A single plant can produce thousands of seeds, which can remain viable in the soil for up to 30 years, forming a long-term seed bank. These seeds germinate readily in disturbed soil, often with peaks of emergence in both spring and fall, ensuring a continuous presence.
Perennial types, particularly Creeping Speedwell, employ vegetative reproduction. Its stems grow low to the ground and root at every node that touches the soil, forming dense, interconnected mats. Even small stem fragments, easily carried by lawn mowers or garden tools, are capable of rooting quickly to form a new plant. The shallow, fibrous root system of these creeping varieties makes them difficult to remove completely and contributes to their rapid area coverage.
Controlling Invasive Speedwell
Managing invasive Speedwell requires an integrated approach that addresses existing plants and the conditions favoring their growth. For small infestations, mechanical removal is an option, but it must be thorough. The fibrous roots and stem fragments of creeping types can easily re-root, so hand-pulling must ensure the entire root system is removed. Any plant material should be disposed of, not composted, to prevent vegetative spread.
Cultural controls are the most effective long-term defense, as Speedwell often exploits thin, weak turf. Maintaining a dense, healthy lawn through regular fertilization, proper watering, and mowing at an appropriate height helps the grass outcompete the low-growing weed. Raising the mowing height, for example, helps shade out the Speedwell, limiting its ability to photosynthesize and thrive.
Where chemical control is necessary, pre-emergent herbicides can be applied in the late fall or early spring to prevent the germination of annual Speedwell seeds. Post-emergent broadleaf herbicides are available for actively growing plants. However, they may require multiple applications because the waxy nature of the leaves on some species can limit absorption.