Speedwells (Veronica spp.) are pretty, blue-flowered perennials that look attractive in a flower-rich lawn. However, their ability to root quickly, even from small sections, means they can quickly get out of hand in both lawns and borders.
What is speedwell?
Slender speedwell (Veronica filiformis) was introduced to Britain from Turkey and the Caucasus during the early 19th century. It was much grown as a rock plant until gardeners realised how invasive it could be. It is now widely naturalised in many parts of the country and is a common and troublesome lawn weed.
Several other species of speedwell are also invasive and can be a weed in lawns and borders.
Slender speedwell (Veronica filiformis) is a low-growing plant with bright blue, long-stemmed flowers early in the year, usually March to May. It is low-growing and can form dense patches in a lawn.
Germander speedwell (Veronica chamaedrys) is a stronger growing, coarser species than V. filiformis, flowering March to August. It is native in grassland, open woodland and hedgerows throughout the British Isles. It is usually troublesome in less frequently mown grass but can adapt to, and survive under, close mowing.
Ivy-leaved speedwell (Veronica hederifolia) and thyme-leaved speedwell (Veronica serpyllifolia) are occasionally troublesome in lawns or borders, the former favouring shadier situations, the latter moister conditions.
Why is speedwell a problem?
Speedwells are perennial plants, producing numerous, slender-branched stems, creeping and rooting at the nodes as they spread to form a dense weed carpet.
The flowers are rarely followed by seeds as the plants are self-sterile and most appear to be from the same clone.
The commonest methods of spread include:
- Stem sections scattered by the mower
- Lawn clippings put on the compost heap, which spread the weed around the garden if the compost is spread before it is completely decomposed
- Nesting birds can spread speedwell while gathering moss from the lawn to line their nests
- Weak grass growth allows the weed to spread
Even when lawn clippings are raked up and disposed of, or the lawn is raked thoroughly to remove moss and weeds, numerous small rooted sections of the weed usually remain.
First, consider whether this can be done using non-chemical means such as digging out or suppressing with mulch. Where these methods are not feasible, chemical controls may need to be used.
Consider non-chemical options first. Speedwell is less likely to be a problem in healthy lawns. Boost grass growth to discourage the spread of the weed by feeding with spring and summer lawn feeds. In autumn, scarify, aerate and top-dress as necessary. See our advice on autumn lawn care and spring and summer lawn care for further information.
Though the lawn should be mown regularly, do not cut it too close, as slightly longer grass will help smother the weed.
Ensure that compost containing lawn clippings contaminated with speedwell is thoroughly broken down before use.
Where speedwells occur in borders, hoe regularly, rake off the weeds and then let them dry out thoroughly before adding them to the compost heap. Alternatively, mulch the bare soil to smother the weeds. Destroy any shoots which succeed in growing through the mulch.
Always read weedkiller labels carefully before buying or using, to ensure you choose a product that is best fit for purpose. Take particular care when using residual weedkillers as these persist in the soil for several weeks or months and can move deeper or sideways in the soil, leading to possible damage of underlying plant roots.
Speedwell in established lawns
Speedwells are resistant to the majority of lawn weedkillers available to amateur gardeners. However, products containing the active ingredient fluroxypyr as one of their ingredients (Scotts Verdone Extra or Verdone Extra Ready to Use) will provide some control in lawns.
Speedwell in new lawns
Weedkillers often cause severe damage if applied to lawns within six months of sowing or turf-laying. Materials containing fluroxypyr as one of their ingredients, however, are claimed to be safe to use after only two months.
Speedwell in beds and borders
Spot treat using the non-selective weedkiller glyphosate, taking care to avoid all contact with cultivated plants. Glyphosate is most effective between June and September. Use the gel (Scotts Roundup Gel) or ready-to-use spray (e.g Scotts Fast Action Roundup Ready-to-Use, Bayer Glyphosate Ready-to-Use Kills Weeds & Roots, Doff Knockdown Weedkiller Ready-to-Use) on patches of speedwell. Leave the weed for three to four weeks for the weedkiller to take effect, before removing dead foliage.
Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see sections 1b and 4)
Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broad-scale weedkillers