Irish gardeners could be breaking the law without even realising it

Irish Daily Mirror

21-05-2025

Summer is just around the corner, and with the warmer weather Ireland has been enjoying lately, many people will be looking forward to spending more time outdoors and tending to their gardens. However, before you get too comfortable, it's important to be aware that not all plants in your garden are harmless - and some could even land you in legal trouble.
One of the most problematic invaders is Japanese knotweed, a fast-growing, non-native weed that many gardeners might unknowingly have on their property. This plant isn't just a nuisance - it's illegal to plant, spread or allow to grow under Irish law. If found, it must be controlled and eradicated immediately to avoid legal consequences.
Under Regulation 49 (2) "any person who plants, disperses, allows or causes to disperse, spreads or otherwise causes to grow Japanese knotweed or any of the other invasive plants listed in the Third Schedule of the European Communities (Birds and Natural Habitats) Regulations, 2011 (S.I. No. 477 of 2011) shall be guilty of an offence".
Japanese knotweed is a fast-growing green shrub that can quickly take over gardens, forming dense thickets during the summer months. According to Ireland's National Biodiversity Data Centre, it can reach up to three metres in height and is often mistaken for bamboo due to its hollow, jointed stems.
In early spring, the plant begins to emerge with small red buds that develop into shoots shaped like asparagus tips. As it grows, the stems become green with noticeable red or purple flecks, while the leaves are lush green and arranged in a distinctive zig-zag pattern along the stems.
By late summer, clusters of small creamy-white flowers appear, making the plant even more recognisable. Come winter, the visible parts of the plant die back, leaving behind brown, cane-like dead stems that may still carry browned flower remnants.
Beneath the surface, Japanese knotweed has an aggressive root system made up of rhizomes - underground stems with an orange centre that snap cleanly like a carrot when bent. These roots are capable of spreading quickly and regenerating even from small fragments, making the plant especially difficult to remove.
According to experts from insurance comparison website Quote Devil, the presence of the weed can cause issues if you are selling or buying a property, and can cause thousands of euros in repair costs. Spokesperson Conor Mulcahy said: "Japanese knotweed can have devastating effects. The roots can interfere with drainage pipes and other structures, blocking and sometimes lifting pipework. A house's underground infrastructure is also at risk which can cost thousands of euros in repairs.
"Japanese knotweed damage is not often covered by home insurance policies and if you look to sell your home in the future this could cause huge problems as it could put off potential buyers. It can also affect your ability to get a mortgage on a new home if there's evidence of Japanese knotweed on the property.
"The first sign of Japanese knotweed tends to appear in spring, when the plant grows and shows clear signs of its presence which is why you should start to look for signs over the next few months to see if you have this pesky plant on your property.
"It's important to keep an eye out for this plant as early as possible, as the more it sets in, the harder it is for experts to effectively remove as it grows and spreads rapidly."
1. Red and purple shoots that look like asparagus
The plant's shoots are red or purple in colour and resemble asparagus coming out from the ground. Shoots of the plant tend to appear in April and May when the ground thaws, allowing the dormant plant to grow (and fast). If you spot growth over a small number of days this can be a telling sign.
2. Heart-shaped leaves
The leaves of a Japanese knotweed are shaped like love hearts which can make them easily identifiable. Colour-wise they are a lush green with reddish veins and can be as tall as 20cm in length.
The leaves always grow on alternative sides and have a distinctive zig-zag pattern.
3. Clusters of small white flowers
In the warmer months of summer, the Japanese knotweed plant bears creamy clusters of white flowers that are small in size. If you spot these, this is bad news as it means the plant has established itself quite strongly, making it difficult to remove.
4. Bamboo-like stems
The stems of a Japanese knotweed plant once grown out of the ground are speckled with flecks of purple. The mature stems are often mistaken for bamboo as they are hollow and become dry and brittle in winter.
5. Brown rhizome roots
If you spot rhizome roots on your property this could be a huge issue. Japanese knotweed has brown roots that are orange and yellow on the inside and these hardy rhizome roots are very difficult to remove. It's easily snapped which can cause it to spread without the proper treatment. The root system, if not treated correctly, can shock the plant in a dormant state making it harder for even an expert to kill.
If you suspect Japanese knotweed on your property, it's important to seek professional advice for safe removal and control. By doing nothing, it could be considered an offence by allowing it to be dispersed or spread. Early treatment not only helps avoid legal trouble, but also prevents more costly and difficult removal down the line.
For more information, see Ireland's National Biodiversity Data Centre's Japanese knotweed information sheet here.