Problem pavement plants

Most plants that are allowed to establish themselves in pavement cracks are annuals with shallow roots, meaning that the entire plant will naturally die off at the end of the season. As a result, these shallowrooted plants are unlikely to compromise the structural integrity of our pavements.

Depending on where they grow, some of these plants may present a trip hazard to pedestrians or obstruct wheelchair users or those with buggies and pushchairs. Thankfully, they can usually be easily removed from walkways and cross-points.

In most cases pedestrian footfall prevents ‘annuals’ from growing in busy areas. This means that trip hazards are not that common, as significant plants tend to be confined to areas of the pavement that people don’t use.

There are a few types of plants that can present a structural risk. Perennials, which develop woody stems, such as trees and shrubs, quickly send down deeper roots.

These are more easily removed when they are young. In addition, some introduced street trees, like the Black Locust tree from North America or the Foxglovetree from China, have started showing a tendency to seed themselves on pavements and grow quickly if allowed to establish.

Butterfly-bush

This popular garden shrub, with pretty purple and orange flower spikes, is native to China and Japan, and as its common name suggests it attracts butterflies. Outside of gardens it spreads vigorously along streets and railway lines if it gets the chance and can be invasive in green spaces. Seedlings pop up in pavement cracks and on walls, and its roots are thought to damage the mortar between bricks. Removing seedlings which pop up and encouraging gardeners to remove flower heads once flowering is over would be advisable.

Another popular garden plant, red valerian flowers for a long time and is a favourite of a variety of insects, particularly the spectacular hummingbird hawk moth. Despite these positives, it grows in clumps and is woody-based, so if found growing on the pavement it’s best pulled out before it spreads, which it will do with ease if left to its own devices.

Flowers can be pink or white as well as the more usual red.

Tree-of-heaven

This deciduous tree is native to China and is easy to recognise from its long stems of paired leaves which turn red in the autumn, sprays of cream-coloured flowers and clusters of winged fruit. Like Butterflybush it is invasive and also can be spotted lining railway tracks. Seedlings pop up on pavements, on walls, in gardens and on waste ground. It’s relatively easy to remove when small so it is best to weed out seedlings as soon as they are identified.

The easiest way to identify an ash tree sapling is by its leaves, each one made up of 9-13 smooth or finely toothed leaflets. While the ash is a tree beloved by many, it can spread quite freely, and shouldn’t be allowed to grow on the pavement in case it starts to cause damage.

Sycamore, like ash, can spread easily due to being extremely adaptable, and will often be seen growing from cracks in the pavement. Look out for their easily recognisable leaves which have five lobes and are attached to distinctive reddish stalks.