14 Perennial Plants That Can Become a Garden Nightmare

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Creating a vibrant and thriving garden often involves carefully selecting plant species that enhance the landscape while coexisting harmoniously. Among these options, perennial plants frequently emerge as favorites due to their ability to return year after year with minimal effort.

While these plants may initially seem alluring due to their robust growth and attractive blooms, they can quickly transform into persistent invaders that are difficult to control. Here are perennial plants that, despite their initial charm, are problematic in many gardens.

Mint (Mentha spp.)

The problem is that once mint takes hold, it can spread like wildfire through underground rhizomes, colonizing garden beds and edging out other desirable plants. If you prefer to keep that mint in, a great alternative is to plant them in containers.

Daylilies (Hemerocallis spp.)

Daylilies can out-compete other plants in the garden, and quickly take their place if they are not removed. Their tuberous roots and self-seeding also allow them to freely spread out of bound.

Phlox (Phlox paniculata)

It is a garden staple because of its colorful summer blossoms but the garden phlox can attract powdery mildew and will self-seed abundantly. It can become a weed proliferating and spreading all over the garden.

Ajuga (Ajuga reptans)

Ajuga or Bugleweed is a mostly used for ground cover which have the desirable foliage and purple flowers. Unfortunately, it can easily go rogue, becoming highly invasive through runners. It takes over most of the mixed beds midsummer, although it can be great for controlling erosion.

Creeping Jenny (Lysimachia nummularia)

Creeping Jenny, or Lysimachia nummularia, is a ground cover plant known for its rapid spread, especially in moist, shady areas. It features bright green leaves and yellow summer flowers, adding visual interest to gardens. Regular maintenance, like trimming and growth monitoring, is necessary to prevent it from becoming invasive and overtaking other plants.

Lemon Balm (Melissa officinalis)

Lemon balm is also a member of the mint family and will take over your garden if not managed properly. The scent of its foliage is delicious but, unless you keep it within bounds it could become an entire community. You might want to grow it in containers to prevent infestations.

Catmint (Nepeta spp.)

Catmint is drought tolerant and has a long blooming period. However, it can become aggressive in some areas, self-seeding readily and spreading into neighboring gardens. Regular trimming and deadheading can help manage its growth and prevent it from becoming too dominant.

Horehound (Marrubium vulgare)

Photo Credit: Eugene Zelenko/Wikimedia Commons

Horehound is a perennial herb often used for medicinal purposes. Its ability to spread via seeds and root systems can crowd out desirable plants. Regularly removing flower heads before they set seed can help control its spread.

Wild Geranium (Geranium maculatum)

Wild geraniums are have attractive flowers and foliage, but they can spread rapidly and may take over garden spaces. While they are generally less aggressive than other perennials, regular monitoring is essential to prevent them from outcompeting other plants.

False Spirea (Sorbaria sorbifolia)

False spirea is a hardy shrub known for its vibrant summer blooms and is suitable for various environments. While it adds color to gardens, it can be invasive if not managed. To maintain its beauty as an addition to any garden, utilize root barriers and conduct regular pruning to control its spread.

Sedum (Sedum spp.)

While many sedums are valued for their hardiness and drought resistance, some varieties can become overly aggressive in garden beds. They can spread rapidly, often through self-seeding, which may lead to crowded spaces. Choose slower-growing sedums to mitigate this risk.

Russian Sage (Perovskia atriplicifolia)

Russian Sage is a perennial valued for its silvery stems and lavender-blue flowers. However, it can spread aggressively through seeds and suckering roots, potentially overwhelming other plants. Regular pruning, deadheading, and the use of root barriers are recommended to control its growth.

Black-eyed Susan (Rudbeckia hirta)

Black-eyed Susan is a vibrant perennial known for its yellow petals and dark cone. While attractive to pollinators, it can become invasive in gardens by spreading through seeds and rhizomes. Regular deadheading and using physical barriers to contain its roots are recommended to prevent it from crowding out delicate plants.

Bamboo

Bamboo is a grass that often proliferates and invades a garden. Once it has taken root, it’s pretty challenging to get rid of—for one, the woody roots go deep underground and often begin shooting new culms even if you cut the plant down. Plant bamboo in a container or pot to help control its growth.

Disclaimer: This list is solely the author’s opinion based on research and publicly available information.