(Veronica species) Although speedwells’ blue flowers look attractive, these creeping perennial weeds can spread significantly and can smother other plants and takeover the garden.
What are speedwells?
Some Veronica species are highly attractive ornamental plants. And although the weedy species, commonly called speedwells, produce lots of pretty blue flowers, these creeping perennial plants can spread significantly and can smother other plants and take over the garden. They are particularly troublesome when they become established in lawns.
The two most troublesome weedy species are slender speedwell (Veronica filiformis) and Germander speedwell (Veronica chamaedrys).
Speedwells grow and root very quickly, soon producing quite large plants. They produce numerous creeping stems that root as they grow, soon spreading to form a dense carpet that can cover large areas of ground, getting out of hand and smothering other low-growing plants. Even small pieces of a plant will grow into larger ones.
In lawns, they can be very difficult to control.
Where do they grow?
- Gravel paths
- Waste or uncultivated ground
Slender speedwell is a low-growing, ground-hugging plant producing hairy stems and rounded or kidney-shaped leaves with blunt teeth. The bright blue flowers are produced on long stems, appearing from the leaf axils (nodes) between April and July, but mainly from March to May.
Germander speedwell can grow to 50cm (20in) tall, but is frequently shorter – especially when growing in lawns, where it then misses the blades of the lawnmower. It is stronger growing and coarser than slender speedwell, producing more triangular leaves. The deeper blue flowers are produced from March to August.
Both speedwells spread through their creeping stems that root at the leaf nodes wherever they touch the ground. Slender speedwell is self-sterile and rarely sets any seeds, whereas Germander speedwell also spreads by seeds.
How to control speedwells
As with most perennial weeds, never allow it to become established. This will make it more difficult to fully control. Early identification and eradication is very important.
Start by digging out as many of the speedwell plants as possible.
Regularly hoeing seedlings and young plants as soon as you see them is the quickest and easiest method of control. The aim of hoeing is to sever the weed stems at or just below ground level, cutting the top growth from its roots. A sharp hoe blade will make this even quicker and easier, so always sharpen the hoe blade before using it. Hoeing on a warm and/or windy day will mean they quickly dehydrate and die.
Digging out the plants when they are more established is more time consuming and more difficult – especially where they’re growing among wanted plants.
Flame guns and weeders that use an electric current are also effective in some locations.
Covering bare soil with weed-control membrane (landscape fabric) or even thick black polythene will exclude light and prevent Germander speedwell seeds germinating. As will mulching the soil with organic matter, such as a bark mulch. For mulches to work properly, they need to be a minimum of 5cm (2in) thick, but 7.5cm (3in) deep works better.
In lawns, regular mowing throughout the year and the use of lawn weedkillers may weaken it and eventually kill it. Although the mower blade may miss the low-lying plants. In which case, rake the lawn before mowing to lift up the creeping stems. Don’t compost the clippings, as this is one way that speedwell is spread around the garden.
There are a number of weed control options available to treat speedwells. In addition to traditional weedkillers there are now also a range of more natural alternatives.
Any weedkiller can be used to control and reduce the spread of speedwells in beds, borders, waste ground and on paths. Those marketed as “fast acting” are contact weedkillers – killing or damaging the plant tissue they are sprayed onto or make contact with. These tend to be based on “naturally-occurring” active ingredients, such as acetic acid and natural fatty acids.
Systemic weedkillers, that also kill the roots can also be used and are more effective.
To ensure the weedkiller works effectively:
- Spray the leaves when the speedwells are growing actively; this is mainly from March/April to September/October.
- The larger the leaf area present, the greater the amount of weedkiller that can be absorbed and move down to the roots. So don’t bother spraying until the leaves have enlarged.
- Use a fine spray to thoroughly coat the leaves in small droplets.
- During the summer, spray in the evening to prevent the spray evaporating and to give maximum time for the spray to be absorbed. In spring or if overnight dew is forecast, spray earlier in the day to allow the spray to dry before dew falls.
- One application of weedkiller may not completely kill all the speedwell present. You may need to spray once, allow the plants to die down, and then spray any regrowth again.
Most contact weedkillers are total weedkillers – that is they will damage or kill any plants whose leaves they are sprayed on. Make sure you keep the spray off wanted plants – including lawns – and, if necessary protect plants by covering with polythene or similar when spraying.
Speedwells are resistant to most lawn weedkillers, but those containing the active ingredient fluroxypyr are effective.
Use weedkillers safely. Always read the label and product information before use.
Keep on top of controlling speedwells when they’re small and young plants. Don’t allow them to become established – especially in the lawn.
- Hand fork
- Hand trowel
- Weed-control membrane
- Lawn weedkillers