Many invasive plants appear harmless or even attractive, but they can have lasting structural, legal, and financial consequences. They may undermine foundations, crack patios and driveways, push out native species, or spread rapidly into neighbouring properties. Left untreated, they could diminish your home's value or make it harder to sell. While some plants can be managed with simple, low-cost methods, others require specialist treatment – and the longer they are left, the more expensive the solution. Spring is the perfect time to inspect your garden. The experts at Propertymark have shared a practical guide to help you recognise seven common invasive plants and address them effectively.
1. Bamboo
This fast-growing ornamental plant is often used for privacy screening. However, it spreads via aggressive underground rhizomes that can travel long distances and punch through asphalt, brickwork, and drainage systems. What to do: Bamboo should be planted in containers lined with strong root barriers to ensure it cannot spread. If planted directly in the ground, within a few years it is common to find new shoots emerging in new locations, so regularly cut back new shoots and remove spreading roots before they establish.
2. Three-cornered leek
A bulbous perennial with triangular stems, drooping white bell-shaped flowers, and a mild onion-garlic aroma when crushed. Three-cornered leek spreads aggressively through bulbs and seeds, squeezing out spring flowers like primroses and violets. What to do: Dig up the entire plant, including the bulbs, before it goes to seed. Dispose of it in general waste rather than composting to prevent further spread.
3. New Zealand pigmyweed
This aquatic succulent has small green leaves and bunches of tiny white or pink flowers. Originally sold in garden centres as an 'oxygenating plant', it swiftly colonises ponds and waterways, smothering native vegetation. What to do: Regularly remove by hand in small ponds and increase shade to inhibit growth. Cover with black polythene for a minimum of three months throughout the growing season and use herbicides cautiously in winter, if necessary.
4. Himalayan balsam
This relative of the busy lizzie with attractive pink flowers spreads rapidly due to its explosive seed pods, which can travel many metres. The celery-like stems can grow more than 3m tall, forming dense growth that smothers other plants. What to do: Hand pull Himalayan balsam when it appears in spring through to the end of August, before the seed pods mature. Alternatively, cut or strim below the first node and apply glyphosate-based herbicide if needed.
5. Rhododendron ponticum
Common rhododendron can grow to many times the height of a person and branches root wherever they touch the ground. The evergreen has glossy leaves and trusses of purple blooms, with each flowerhead potentially producing between 3,000 to 7,000 seeds. What to do: Cut the stems down to ground level and immediately apply a herbicide to the stumps to prevent regrowth. For long-term success, you must also pull up any seedlings and repeat the treatment for several years.
6. Giant hogweed
Resembling oversized cow parsley, giant hogweed grows rapidly and is capable of reaching heights of 3m. Its sap causes severe skin burns and long-term sensitivity to sunlight, posing a serious health risk. What to do: For minor infestations, don protective clothing and cut the root 10 to 15cm below ground level. Apply glyphosate-based herbicide in early spring for more extensive areas or engage specialists.
7. Japanese knotweed
This mother of all invasive plants is notorious for diminishing property values and creating complications during sales. It can inflict serious damage, compromising foundations, walls, and drainage systems. What to do: Eradicating this weed is a daunting task, as a small fragment of root can give rise to a new plant. Seek specialist advice as the most effective approach involves using a chemical spray or, depending on the value of the property, excavation.
"If left untreated, invasive plants can cause significant pounds' worth of damage to your property. It is vital that buyers ask whether a property has been affected, and that sellers are upfront about any issues," said surveyor Michael Holden from Propertymark. Where invasive plants are already well established, homeowners should obtain a professional assessment to identify the species and determine the most suitable course of action. Environet provides a complimentary identification service for homeowners.
