Japanese Knotweed

First introduced as an ornamental garden plant, this aggressive spreader can smoother anything in its path. Its network of persistent roots is known to weave its way along rivers, waterways and waste ground, creating a monoculture.

The roots are so strong they can easily break through pipes and drains underground and even pure Asphalt, with the roots likely to target constructed patio or front porch areas.

Appearance:

• Cream/White coloured Perennial flowers (up to 10cm)
• The average height is 2.1m (7ft), but it can grow up to 3m (9.8ft).
• Light green, heart or shovel-shaped leaves. Specks of red and purple.
• Deep-penetrating Rhizomes (adapted stems)

Chinese Wisteria 

Although this non-native plant may look majestic with its cascading mauve and lilac flowers, it is an extremely vigorous invasive species. 

The growing wisteria rapidly intertwines and climbs up anything in its way, with tendrils quickly becoming strong vines, including evergreen trees and shrubs. Chinese Wisteria can smoother and strangle foliage, trunks and branches, weakening the attacked plant. 

Appearance:

• Can grow 20-30m long (over supporting trees)
• Shiny, green and pinnately compound leaves (10-30cm length)
• White, blue or violet flowers in 15-20cm racemes
• Thick vines, reaching up to 60ft (18m) long.

English Ivy 

English Ivy is one of the best evergreen climbing and trailing plants for hanging baskets, however, this doesn't stop it from becoming incredibly disruptive.

The plant spreads by its system of aggressive, self-rooting stems and surplus of seeds, which are a favourite for birds. This invasive plant works its way up to the highest point to gain sunlight destroying anything in its path.

Appearance:

There are various types of English Ivy, each slightly varying in appearance, including; Golden Curl, Needlepoint, Goldchild and Ivalace, amongst others.

• Greenish-white, greenish-yellow flowers
• Perennial, evergreen climbing vine up to 80 feet high
• Stems are 4-5 inches long.
  

Butterfly Bush

This invasive plant was first used by gardeners to feed and encourage butterflies and hummingbirds into the area. Yet, it now has the reputation as one of the most aggressive invasive plants in the Pacific Northwest.

The bush is a quick seed spreader, quickly overtaking well-drained and sunny areas, overpowering many of the native plants and ruining local ecosystems. You're likely to see this invasive species in wastelands like abandoned mines or railroads. 

Appearance:

Again, there are a few different types of the Butterfly Bush, with their size, flowers and level of invasiveness varying with each.

• Long, drooping panicles and conical flower clusters bloom (shades of purple, white, pink, and orange)
• Can grow up to 12ft in height, with dwarf versions maintaining 2-4ft
  

Japanese Honeysuckle

Spreading across the ground or winding up trees, this climbing invasive species can smother almost anything in its way.

Japanese Honeysuckle has a plethora of seeds and aggressively spreads using its self-rooting system. The invasive species thrive in the shade or sun and is often found along the US East Coast. 

Appearance:

• Tiny white fragmented trumpet-shaped flowers
• Height of 15-30ft (4.6 to 9.1m)
• Opposite oval leaves (3-8cm long & 2-3cm wide)
  

Japanese Barberry 

Japanese Barberry is a deciduous shrub with thick thorns along the stems for defence, although this doesn't stop birds from eating the fruits and unintentionally spreading the plant further.

It is often used in gardens as a boundary plant owing to its dense and easily trimmed nature, although it can rapidly monopolise deciduous forest floors. 

Appearance:

• Orange-Red Berries
• Height of 5ft (1.5m)
  

Kudzu Vine

This vine is extremely aggressive and can smother native plants easily, as well as break-even mature tree branches owed to its weight.

Kudzu vine was originally used to shade porches in US southern plantations, but it quickly spread using various methods; seed dispersion and sprawling rooting systems. The plant can quickly engulf anything from whole forests to man-made structures (houses, signs etc.)

Appearance:

• Woody, slightly hairy vines up to 18m (60ft)
• Long racemes with reddish-purple flowers
• Flat, hairy seed pods
  

Chinese Or Japanese Silver Grass

This once adored perennial plant is now regarded as an incredibly invasive species, known to colonise any disturbed grounds (forest edges, roadsides or old fields).

Chinese/Japanese Silver Grass spreads easily via its network of extensive roots and rhizomes, as well as its self-seeding nature. The grass is incredibly flammable, and wildfires are much more likely in monogamous dry, grassy areas. 

Appearance:

• Huge, dense clumps (up to 12ft high)
• Tassel-like flowers (silver, pink and rustic coloured)
• Tall blades of the grass arched over
  

Winter Creeper

Winter Creeper is a robust vine known to invade forest openings, spread seeds across the ground and climb up trees by clinging to the bark.

Its vigorous root system can survive in poor quality soils and the sun or shade. Native plants can quickly be starved with low-growing varieties. 

Appearance:

• Can grow up to 40 to 70 feet (12-21 m.)
• Glossy, dark green leaves (1-3 inches long) (2-7cm)
• Tiny green flowers become long-lasting small berries for birds
  

Running Bamboos

There are two kinds of bamboo; clump-forming and running bamboo. The first rarely becomes uncontrollable whilst the latter will send out unstoppable shoots that can even break through concrete and asphalt!

It was first introduced as an ornamental plant, adored for its exotic look and is still widely sold even though some varieties are classed as invasive and they can cause extensive damage. 

Appearance:

• Height of up to 30ft (9.1cm) or more
• Pale yellow to almost white
• Uniform, straight growth