22 Perennials That Will Take Over Your Garden (And Not in a Good Way)

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Not all perennials are a dream come true for gardeners. While many provide beauty and long-lasting blooms, some come with unexpected challenges that can turn gardening into a frustrating battle. Whether they spread aggressively, require constant upkeep, or even pose health risks, these plants can quickly become more trouble than they’re worth.

Some perennials are invasive, aggressively taking over garden beds and crowding out native plants. Others spread so rapidly that they dominate the space, making it difficult for other plants to thrive. Certain varieties demand far more attention than the average gardener wants to give, while some weeds disguise themselves as perennials, fooling even experienced gardeners.

Beyond maintenance concerns, some perennials can trigger allergies or are toxic to pets and people, adding unexpected risks to the mix. If you want a thriving, low-maintenance garden without unexpected headaches, it’s best to think twice before planting these problematic perennials.

Japanese Honeysuckle (Lonicera Japonica)

Japanese honeysuckle may look enchanting with its delicate, sweetly scented white-to-yellow blooms, but don’t be fooled—this fast-growing vine is quite aggressive. Japanese honeysuckle is a fast-growing, twining vine with fragrant white to yellow flowers.

It outcompetes native vegetation by forming dense mats that smother plants. Left unchecked, it can take over fences, trees, and entire sections of a garden, making it a challenge to control. To get rid of Japanese honeysuckle, regularly cut back the vines and apply a systemic herbicide to the cut stems.

Chinese Wisteria (Wisteria Sinensis)

Chinese wisteria is a climbing vine that produces cascading clusters of fragrant purple flowers. It is undeniably beautiful, but its aggressive growth can quickly turn it into a garden nightmare.

This fast-spreading vine tightly coils around trees, shrubs, and structures, eventually forming dense mats that smother surrounding vegetation. Its ability to outcompete native plants makes it a serious threat to local ecosystems, often leading to the decline of other species in the area.

Controlling Chinese wisteria requires persistence. Regularly cutting back the vines can help keep them in check, but for long-term removal, applying a systemic herbicide to freshly cut stems is the most effective approach.

Bugleweed (Ajuga reptans)

With its rich green, bronze, and purple-hued foliage, bugleweed is eye-catching. This vigorous, low-growing perennial is excellent for suppressing weeds and stabilizing soil, making it a popular choice for erosion control. Thriving in partial to full shade, it fills large, difficult-to-plant areas where other species might struggle.

However, bugleweed doesn’t always know when to stop. Its rapid runners extend far beyond its intended space, quickly overtaking garden beds, lawns, and neighboring plants. While it’s low-maintenance, keeping it under control requires regular trimming and the removal of unwanted shoots. Because of its aggressive spread, bugleweed is best suited for large spaces where its tendency to take over won’t become a problem.

Mint

Mint can be useful for teas, flavoring, and digestive health. However, while mint is undoubtedly useful, it’s also one of the most notorious garden invaders.

This fast-growing perennial spreads aggressively through underground runners, quickly overtaking garden beds and choking out neighboring plants. It thrives in a wide range of conditions, adapting easily to various soil types and sun levels, which makes containment a challenge.

Consider growing it in containers or raised beds to prevent it from spreading uncontrollably. Regular pruning and root management are also essential if planting directly in the ground. While mint is a wonderful herb, it requires careful control to avoid becoming a nuisance.

How to Grow and Harvest Mint

Lamb’s Ear (Stachys byzantine)

With its velvety, silver-gray leaves, lamb’s ear is quite resilient in the garden. This low-growing perennial quickly forms a dense, soft mat, making it a popular choice for ground cover in sunny gardens. Once established, it thrives in full sun, tolerates moderate drought, and requires little maintenance.

However, its ability to spread rapidly can be both a blessing and a curse. Lamb’s ear readily expands beyond its intended space, crowding out neighboring plants and taking over garden beds if left unchecked. Regular thinning and trimming help keep it in bounds.

Giant Hogweed (Heracleum Mantegazzianum)

Giant hogweed is a towering plant with large, umbrella-shaped clusters of white flowers and enormous leaves. It grows in the northeast and northwest U.S. and thrives in moist environments such as riverbanks, forest edges, and ditches.

Contact with giant hogweed sap in conjunction with sunlight exposure causes severe skin burns that can result in permanent scarring.

Bamboo (Phyllostachys Spp)

There are many types of bamboo plants, and some are more invasive than others. The invasive types can rapidly spread and quickly turn into an overwhelming force in the garden. Bamboo plants spread rapidly through underground rhizomes, forming dense thickets that are difficult to control. Bamboo plants can be weakened by cutting down new shoots as they emerge but can be difficult to eradicate altogether.

Stinging Nettle (Urtica Dioica)

Stinging nettle is a perennial herb that grows in moist, nutrient-rich soils across the U.S. The plants have heart-shaped serrated leaves and tiny stinging hairs along the main stem and side shoots.

Contact with stinging nettles causes a painful, burning sensation and skin irritation, often with redness and swelling. Medical treatment is not usually required, but antihistamines and soothing creams can help alleviate symptoms.

Japanese Knotweed (Fallopia Japonica)

Japanese knotweed may resemble bamboo with its tall, hollow stems and heart-shaped leaves, but its aggressive spread makes it one of the most troublesome invasive plants. This fast-growing perennial forms dense stands that crowd out native vegetation disrupt ecosystems and even damage buildings and infrastructure by pushing through foundations and pavement.

Due to its highly invasive nature, Japanese knotweed is classified as a noxious weed, requiring careful management. Its deep, resilient root system makes eradication extremely difficult, often requiring professional intervention. In many areas, its presence must be reported to authorities, who can provide guidance on the most effective removal strategies.

Poison Ivy (Toxicodendron Radicans)

Poison ivy is a fast-growing, aggressive plant that spreads relentlessly along the ground and climbs trees, fences, and structures, covering everything in its path. Found throughout much of the U.S., especially in wooded areas and along field edges, this persistent plant can quickly take over a space if left unchecked.

What makes poison ivy particularly troublesome isn’t just its ability to spread—it’s the severe skin irritation it causes upon contact. The plant’s oils trigger intense itching, redness, and painful blisters that can last for weeks.

In some cases, exposure requires medical treatment, and excessive scratching can lead to secondary infections. Even brushing against the leaves, stems, or roots can transfer the irritating oil, making this plant a serious nuisance for gardeners, hikers, and anyone spending time outdoors.

Butterfly Bush (Buddleja Davidii)

With its fragrant, arching spikes of purple flowers, the butterfly bush is a favorite among pollinators—but its beauty comes with a downside. This fast-spreading shrub produces an abundance of seeds that disperse widely, allowing it to take root in disturbed areas and outcompete native plant life. Butterfly bush can be challenging to control, quickly dominating landscapes and reducing biodiversity.

English Ivy (Hedera Helix)

English ivy’s dark green, glossy leaves make it a popular choice for ground cover and climbing accents – But don’t be fooled because its rapid growth can quickly become a major problem. This evergreen vine aggressively climbs trees, forming thick canopies that block sunlight and weaken or kill understory plants. It can overwhelm gardens, forests, and even structures.

Cutting back the vines won’t stop its spread—its dense root system must be completely dug out to prevent regrowth.

Japanese Barberry (Berberis Thunbergii)

Japanese barberry may add a pop of color to the landscape with its red or green leaves and bright red berries – but its aggressive growth makes it a troublesome invader. This thorny shrub forms dense thickets that outcompete native plants, disrupting local ecosystems and reducing biodiversity.

Privet (Ligustrum spp.)

Privet forms dense thickets of growth bearing small, dark green leaves and white flowers. This shrub was often grown as an ornamental hedge but spread quickly, crowding out native vegetation. Vigorous pruning can slow growth, but herbicide is usually the only way to eliminate privet.

Periwinkle (Vinca Minor)

Periwinkle is a trailing evergreen plant with glossy leaves and blue-violet flowers. Although this plant is very pretty, it spreads rapidly, forming dense ground cover that suppresses native plants.

If you want to get rid of it, repeated pulling or mowing can help weaken it over time, but its aggressive growth requires persistent effort to keep it in check. Without regular maintenance, this seemingly charming plant can take over garden beds, forested areas, and open spaces, outcompeting native vegetation.

Autumn Olive (Elaeagnus Umbellata)

Autumn olive is a deciduous shrub with silvery leaves and small red berries. The vigorous growth of autumn olive crowds out other plants, and it can also disrupt the nutritional balance of the soil. The most effective way to get rid of autumn olives is to cut down the shrubs and treat the stumps with herbicide.

Burning Bush (Euonymus Alatus)

Burning bush, named for its bright red foliage in fall, is a shrub that grows in dense thickets. Birds spread the seeds, and they quickly outgrow native plants. To control burning bush, pull out smaller plants by the roots and cut back larger plants before they go to seed.

Oleander (Nerium Oleander)

Oleander is often found in gardens and roadsides and bears fragrant white, pink, or red flowers. Contact with oleander sap can cause skin irritation and more serious health issues if it enters the bloodstream through cuts. The effects can be temporary but potentially serious, and medical treatment is recommended for severe exposure.

Mimosa Tree (Albizia Julibrissin)

Mimosa is a small deciduous tree with fern-like leaves and delicate fluffy flowers. It spreads rapidly via seed spread and its extensive root system, allowing it to invade and dominate open areas and forests. Large mimosa trees can be killed by ring-barking – removal of the bark from the lower trunk – and cutting back all new shoots as they emerge.

Water Hyacinth (Eichhornia Crassipes)

Water hyacinth is a floating aquatic plant with thick, glossy leaves and violet flowers that was introduced as an ornamental plant for garden ponds and lakes. It forms dense mats on water surfaces, blocking sunlight, reducing oxygen levels, and impeding water flow. The only way to eradicate water hyacinths is to remove them from waterways manually.

Tree of Heaven (Ailanthus Altissima)

The tree of heaven may have a celestial name, but it is bad news in our gardens! This deciduous tree produces allelopathic chemicals that inhibit the growth of nearby plants, allowing it to spread rapidly and form dense stands. To eradicate the tree of heaven, cut down all growth and apply herbicide to the stumps.

Rhododendron (Rhododendron spp.)

Rhododendron is an evergreen shrub with large, showy flowers in a variety of bold colors. Contact with rhododendron leaves or flowers can cause skin irritation, redness, and swelling. Medical treatment is usually unnecessary, but soothing creams can help alleviate symptoms.

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While we may tolerate certain weeds like dandelions, most gardeners aim to remove these undesired plants from their gardens—for good. To help you get rid of weeds in your garden, here are 12 natural methods to consider.

12 Natural Ways to Get Rid of Weeds in Your Garden

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