Weeds between patio slabs: why they keep coming back

If you have a patio, a path or a paved front garden in London, you know the problem. You pull the weeds out, and a few weeks later they are back in exactly the same joints. Here is why, and what actually helps.

Why the joints fill up with weeds

The gaps between slabs collect everything: grit, dust, fallen leaves and bits of moss. Over time that breaks down into a thin layer of soil, and that is all a weed seed needs. Shady, damp patios behind terraces and blocks of flats are the worst for it, because the joints never fully dry out.

Some weeds also have roots that go deep. Dandelions and docks grow long tap roots, and if you snap the top off, the root simply grows a new plant.

Getting them out properly

• Pull the root, not just the leaves. A weeding knife, or an old kitchen knife run along the joint, gets right down to the root.
• Brush out the debris. Once the weeds are out, sweep the joints clean so there is less for new seeds to grow in.
• Clear the drainage channels. The channel drains along patios and garages fill with soil and weeds too. A blocked drain means standing water, and standing water means more moss and weeds.
• Do it before they seed. One dandelion clock can put hundreds of seeds back into your patio. Weeding in spring and early summer, before they flower, saves work later in the year.

Will a pressure washer fix it?

A pressure washer makes slabs look clean and blasts a lot of debris out of the joints. It can also wash out the jointing material, which leaves even more room for weeds. If your joints are already open and crumbly, they may need filling again to really solve the problem.

What about weedkiller?

Weedkillers work on many weeds, but read the label carefully, keep them away from pets, ponds and drains, and never spray on a windy day. Plenty of people prefer to avoid them altogether, especially near children and wildlife. Weeding by hand takes longer, but it leaves nothing behind.

How often?

In a typical London garden, weeds in paving come back through spring, summer and early autumn. A good clear-out in spring and another in late summer keeps most patios under control. A very shady or damp patio may need it more often.

Our patio jobs

The photos in this post are from one of our own jobs in London, where weeds had grown up through every joint and along the drain. You can see more like it on our work page.

If yours has got out of hand, we will weed it for you. Have a look at our weeding service.