10 Flowering Perennials You Should Avoid in Small Spaces

Large, rapidly spreading or invasive perennials can become more trouble than they’re worth in small spaces. Gardening expert Madison Moulton lists 10 perennials best avoided in small gardens and what you can plant instead.

Pink flowering perennial with tall stems and many pink blossoms in bloom in the summer sun.


I often dream of gardening in wide open spaces where I can plant anything my heart desires without space or budget constraints. Unfortunately, that’s just not a reality for me, and it isn’t the reality for most gardeners.

As urban areas expand, garden space shrinks. With this change comes a need to choose plants carefully to make the most of prime backyard real estate. It’s important to avoid flowers that tend to take over, especially if you don’t want to spend all your time controlling growth rather than enjoying it.

Although undoubtedly beautiful, these perennials are best kept out of small garden spaces. Luckily, there are always wonderful alternatives that won’t give you the same trouble.

Butterfly Bush

Close-up of a flowering Buddleja davidii bush in a sunny garden. The plant has long clusters of bright pink flowers. The flowers are small, tubular, with an orange throat. The greyish-green, lanceolate-shaped leaves make a great backdrop for the vibrant flowers.
Butterfly bush is a popular choice for attracting pollinators like butterflies.

If you’re looking to attract pollinators to your garden – and particularly butterflies – you’ll probably see butterfly bush high on the list of recommendations. Scientifically known as Buddleia davidii, the butterfly bush features adorable purple flowers that are beloved by gardeners.

Unfortunately, planting butterfly bushes in your garden (and especially a small garden) can have negative effects that outweigh their aesthetic benefits.

This plant is considered invasive in many regions across the US, self-seeding to spread not only around your garden but to nearby habitats too. The vigorous growth smothers native plants and can quickly get out of control in warm climates. This is top of our list of flowers to avoid in small spaces.

Coneflowers (Echinacea) are great alternatives that attract even more pollinators and can be used for a pop of purple color, depending on your chosen species. The plants remain much more compact and manageable than butterfly bushes, ideal for small spaces.


Close-up of blooming Wisteria in the garden. Wisteria is a vibrant and woody vine known for its stunning cascades of fragrant flowers. The flowers hang in long, drooping clusters called racemes and come in shades of purple and white. The leaves are compound and consist of several leaflets that give the vine a lush appearance.
Mature wisteria is unsuitable for small gardens due to its size and aggressive growth.

One look at a mature wisteria will give you the first reason why it’s not suitable for small gardens – size. This climber is large and needs a tall, tough support to grow to its full potential.

But even if you’re willing to make the space, there is a more important reason it should be avoided. Wisteria is an aggressive plant that will quickly take over your backyard if not controlled. This may be useful for quickly covering a pergola or garden arch, but the roots will spread to crowd out other plants in your garden and may even damage other structures.

Wisteria sinensis, commonly known as Chinese wisteria, is just one of a few varieties declared invasive in several eastern states and is a great risk to plant in a small space. Instead, you can try climbing hydrangeas with the same uses and without the aggressive spread.

Plume Poppy

Close-up of Plume Poppy (Macleaya cordata) in the garden. It is a herbaceous perennial known for its tall growth and showy feather-like flowers. The plant produces large leaves with deep lobes. Plume Poppy produces tall stems topped with panicles of tiny star-shaped flowers in shades of white or pink.
These poppies are controversial due to their invasive nature and towering height.

The plume poppy (Macleaya cordata) is not a true poppy. It doesn’t belong to the genus Papaver but is part of the poppy family (Papaveraceae), much like California poppies. However, plume poppies aren’t quite as beloved as their relatives and are controversial choices for gardeners.

The controversy stems from the invasive nature of these plants, particularly in warm climates. Both the rhizomes and seeds quickly spread to take over small gardens if not rigorously controlled, making it a high-maintenance (and generally not worthwhile) choice. Another reason to avoid these flowers in small spaces: they also grow to a towering 8 feet tall, leaving little room for other plants.

If you’re looking for height, try growing the popular cottage garden staple hollyhocks (Alcea rosea) instead. They grow vertically without taking up too much horizontal space and have similar foliage to enjoy when the plant is not in flower.

Lily of the Valley

Close-up of a Lily of the Valley (Convallaria majalis) flowering plant. It is a charming and fragrant perennial plant. Its lanceolate leaves emerge from the ground in a lush green carpet. The plant produces delicate, white, bell-shaped flowers that hang from curved stems, exuding a sweet and intoxicating aroma.
Lily of the valley is unsuitable for small gardens due to its aggressive spreading nature through rhizomes.

Those needing to fill shady gardens might consider the adorable woodland plant Convallaria majalis, commonly known as Lily of the Valley. But unless you’re willing to deal with its spread for years to come, you may want to avoid this flower in your small garden space.

Lily of the Valley has aggressive rhizomes that spread underneath the soil undetected. You’ll notice the signs of this rapid spread every spring when new plants start to pop up out of nowhere, potentially spreading far from where you initially planted.

This plant may be a wonderful symbol of spring, but it’s not ideal for small spaces if you plan on growing anything else in the same area. For similar flowers, try snowdrops (Galanthus nivalis) or plant in containers where the rhizomes can’t become an issue. It’s also toxic to animals, which means it’s not ideal if you share your home with pets.

Sweet Autumn Clematis

Close-up of blooming Sweet Autumn Clematis in the garden, against a blurred green background. Sweet Autumn Clematis is a vigorous and ornamental vine with an abundance of small, star-shaped white flowers. These flowers form dense clusters, making for a spectacular sight. The bright green leaves of the plant consist of three leaflets and provide a lush backdrop for an abundance of flowers.
Sweet autumn clematis with fragrant white flowers is invasive and aggressive in growth.

Clematis terniflora, or sweet autumn clematis, has eye-catching white flowers with a wonderfully sweet scent. Popping up in late summer and flowering into fall, the carpets of flowers make this vine a very tempting option.

Unfortunately, Clematis terniflora has an aggressive growth habit, making it a flowering vine to avoid in small spaces. The vines spread rapidly to smother nearby plants, and the flowers release seeds that spread to other habitats nearby. It’s invasive in some eastern states. The vines also grow beyond 10 feet tall, making them larger than many small gardens can accommodate.

Luckily, other clematis species aren’t as aggressive, such as the native Clematis virginiana. But if you’re short on space, you can also opt for the fragrant but often shorter jasmine vines.


Close-up of blooming Loosestrife (Lysimachia spp.) in the garden. The plant produces small bright yellow star-shaped flowers. The flowers are borne in thorns or clusters, adding a charming vertical element to the garden. The leaves of loosestrife are lanceolate with serrated edges.
The Lysimachia genus offers colorful flowers like gooseneck loosestrife and creeping jenny.

Plants in the Lysimachia genus, commonly known as loosestrife, are largely known for their eye-catching flowers in many colors. Gooseneck loosestrife (Lysimachia clethroides) is a popular option for its structural flowers while creeping jenny (Lysimachia nummularia) is a popular ground cover.

Although they are related, this genus doesn’t include the invasive Lythrum salicaria or purple loosestrife. But it’s best to avoid growing any Lysimachia in your backyard for a similar reason. It becomes difficult to control due to vigorously-spreading rhizomes and traveling seeds.

For a similar floral look on a more compact and easier-to-manage plant, try spiked speedwell (Veronica spicata). The flowers come in various colors and grow to a maximum of 3 feet, depending on the cultivar.


Close-up of a blooming periwinkle in the garden. It is a charming evergreen groundcover known for its small flowers and glossy leaves. The flowers are open, funnel-shaped, bright blue. The leaves are tall, oval, shiny, dark green.
Periwinkle flowers can become invasive and harmful to your garden.

Adorable periwinkle flowers may look inconspicuous and suitable for any space – including small gardens. But don’t let this look fool you. Species in the Vinca genus can be quite dangerous around your garden and to neighboring environments when uncontrolled.

Two of the most popular species are Vinca major (greater periwinkle) and Vinca minor (common periwinkle). In warm climates, these plants are often classified as invasive, particularly the larger Vinca major. These flowers have the ability to quickly take over small backyards and smother any plants that get in their way.

For a low-growing native option, wild blue phlox (Phlox divaricata) sports flowers with a similar shape and color. Woodland phlox is also impressively easy to grow and adapts well to varying conditions across the US.


Close-up of blooming Crocosmia in the garden. Crocosmia, commonly known as montbretia, is a vibrant flowering plant cherished for its striking blooms and sword-like foliage. The leaves are long and lanceolate, resembling narrow plates of bright green color. The flowers are borne on tall curved stems. They are tubular, bright red. The flowers are arranged in loose inflorescences along the stems, creating a striking spectacle reminiscent of flying hummingbirds.
These showy flowers are attractive to hummingbirds and birds but can be invasive.

Crocosmia flowers are not just popular among gardeners, but butterflies and birds too. Most famous for attracting hummingbirds, members of this genus are great choices for injecting life into your garden. But, if you’re working in a small space, you may want to choose your coppertips very carefully or avoid these flowers altogether. 

While not all crocosmia cultivars are problematic, there are a few that gardeners short on space should avoid. Several types are known to spread rapidly and quickly become out of control, conquering small spaces in no time. Crocosmia crocosmiiflora (Montbretia) is the main culprit to avoid, but there are a few others to watch out for.

Tried and tested named crocosmia cultivars are far safer options, especially for compact varieties that work in a small garden. Cardinal flowers (Lobelia cardinalis) are a little taller but have similar blooms that also attract pollinators.

Obedient Plant

The leaves of an obedient plant are lanceolate in shape and have a serrated edge. They are arranged in opposite pairs along erect stems. The stems themselves can grow to a height of 2 to 4 feet, creating a bushy and upright appearance. The leaves and stems are often covered in fine hairs, giving the plant a slightly fluffy texture. The flowers are tubular and have a characteristic two-lipped structure. They are purple and white.
Physostegia virginiana, or obedient plant, may be named for its flexible stems, but it’s invasive.

Given its common name, you may be surprised to find Physostegia virginiana on this list. However, although the stems and flowers may be ‘obedient’ in movement, this species’ growth habit and spread is anything but.

Like mint, a close relative, obedient plant may take over any beds it’s planted in, smothering any plants that get in its way. This plant should be avoided in small spaces unless you regularly dig up spreading rhizomes and deadhead before the seeds can travel around your backyard.

The ‘Miss Manners’ cultivar doesn’t cause as much trouble, making it a better choice for small gardens. You can keep the plant confined to a container, but you must still stop the seeds from spreading. For similar flowers, try planting the annual snapdragon each year instead.


Close-up of a blooming Bugleweed in a sunny garden. It is a low growing perennial herbaceous plant prized for its attractive foliage and clusters of small brightly colored flowers. The leaves are spear-shaped, dark green in color with a slight purple-bronze tint along the edges. The leaves have a slightly scalloped or serrated edge. The flowers rise on vertical spines above the foliage. The flowers are tubular and bilabiate. They are bright purple.
Ajuga reptans is a quick-spreading groundcover that becomes invasive in small gardens.

Ajuga reptans is a popular perennial groundcover often used to fill empty spaces and crowd out other weeds. But if it’s not controlled, it can grow like a weed (hence the name) and is declared invasive in several states, including Maryland and Oregon.

For large gardens with lots of open space, the rapid spread of bugleweed is a benefit. But in small gardens, it will quickly become a nightmare. Rather than dealing with this plant when it inevitably gets out of hand, it’s best to avoid planting it altogether.

Like periwinkle, wild blue phlox is a well-behaved alternative to bugleweed that may not have the same spreading capabilities but won’t give you any trouble in small spaces.

Final Thoughts

When growing in a small garden, space is at a premium. Rather than filling it with these troublesome plants, choose polite alternatives that complement your landscape rather than conquering it.

A small pod adorned with a mesmerizing waterfall, creating a tranquil oasis in nature. The gentle cascade flows into a serene pond, surrounded by a delightful assortment of plants and blooming flowers, adding a burst of colors to the landscape.


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