The invasive species to look out for in Hackney’s gardens and green spaces

Japanese Knotweed. Picture: PA Photo/thinkstockphotos

Japanese Knotweed. Picture: PA Photo/thinkstockphotos - Credit: Archant

With many of us stuck indoors during the pandemic, our brief opportunities to head outside for exercise have been more precious than ever. But these green spaces are under threat from an army of invasive plants, against which the council is battling.

Himalayan balsam. Picture: Gary Rogers/Wiki Commons

Himalayan balsam. Picture: Gary Rogers/Wiki Commons - Credit: Gary Rogers/Wiki Commons

These plants, which are subject to legal restrictions, can suffocate and starve native wildlife, while some pose a risk to human health.

So next time you’re out in the borough’s parks, or even your garden, these are some of the plants to watch out for:

Japanese knotweed

With stems reaching over 2m, and large white flowers, Japanese knotweed may seem like an attractive-looking plant.

However, its rapid growth and dense leaves make it one of the most persistent invasive plants anywhere in the country. The speed of its growth allows its stems to be able to penetrate asphalt, wiring and even foundations, meaning it can make houses more difficult to sell.

Professional gardener Naomi Schillinger said: “Japanese knotweed doesn’t have any natural predators in the UK, but in Japan, it did. When plants are taken out of their context, they can spread, and with knotweed, as well as others, we didn’t find out until it was too late.”

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The weed is difficult to eliminate, as it is capable of regenerating the entire plant from only small fragments. This has proved a particular problem in Clapton, where fragments of plants carried by the railway have allowed the weed to spread into neighbouring properties. In 2017, treating just one of these properties cost the council some £3,000.

Other areas of the borough affected by the weed include Stoke Newington, Hackney Downs and Woodberry Downs. Due to the potential amount of knotweed across council properties, Hackney Council is considering the business case for hiring staff to deal with the issue - which would cost around £35,000 a year.

A council spokesperson said: “Japanese knotweed must not be placed in garden waste or general rubbish and must be disposed of properly as per governmental advice on treating and disposing of invasive plants.”

Giant hogweed

Originally from southern Russia, giant hogweed lives up to its name, being able to grow to over 3m in height.

Its large clusters of white flowers sitting atop green and purple stems made it attractive to Georgian Gardeners, who first imported it to Kew in 1817. It should not be confused with the native hogweed, which grows widely across the UK but is generally much smaller.

However, its sap is dangerous to human health. It contains phototoxic compounds which weaken the skin’s ability to protect itself from UV rays, causing anything from a rash to severe burns. Repeated exposure can, in very severe cases, cause damage to tissues deep within the body.

According to council records, Giant Hogweed has been present in Hackney’s parks and green spaces for at least the past decade. Hackney Marshes, as well as neighbouring Mabley Green, are both known to have populations of Giant Hogweed.

Himalayan balsam

A large relative of the garden favourite Busy Lizzie, Himalayan balsam was once appreciated for its large pink flowers and large size, growing to around 3m in height.

But since being brought to the UK by the Victorians in 1839, it has spread rapidly, particularly by bodies of water. It uses this water to help it spread, while research suggests it can also destabilise river banks, making them vulnerable to collapse.

Though it is an annual plant, its quick growth and large size allows it to starve other plants of light, and can exploit these low-light conditions to spread further at the expense of native species.

Himalayan Balsam was previously present in Haggerston’s Acton Estate. However, the council was able to identify it and remove it while it was still small, preventing it from spreading.

What to do

As these plants are listed under Schedule 9 of the Wildlife and Countryside Act 1981, it is illegal to plant these species, or cause them to grow, in the UK. Doing so can result in a fine or up to two years in prison. Allowing them to spread to neighbouring properties can also be considered antisocial behaviour, which can also result in legal action.

While some of these plants can be dealt with using weedkillers, it is worth receiving advice if these plants are found on your property. In particular, Japanese Knotweed is considered to be controlled waste, often requiring specialists to fully eradicate it and remove its remains. If you see these plants in public spaces, you should alert the council to its presence.

These plants are just some of the many damaging invasive species found in the capital, which range from other plants such as floating pennywort to animals such as oak processionary moth.

The council spokesperson said: “External bodies advise us on local biodiversity on a consultancy basis. [We] are working with a project advisory group on a green infrastructure strategy which includes the borough’s Parks and Green Spaces Strategy and Biodiversity Action Plan. This will inform guidance on preparing green infrastructure strategies being developed for London Boroughs by the Greater London Assembly.”