Introduction
There is a unique kind of excitement that builds as the weather warms and the first green dahlia sprouts begin to poke through the soil. For many of us at Longfield Gardens, these dinnerplate dahlias are the undisputed stars of the late summer landscape. Their dinnerplate-sized blooms and intricate geometric patterns bring a level of drama to the garden that few other flowers can match. However, even the most spectacular dahlia looks better when it has the right supporting cast to highlight its beauty and fill in the gaps.
Choosing what to plant with your dahlias is an opportunity to turn a simple flower bed into a professional-looking garden design. Whether you want to attract more pollinators, deter common pests, or simply ensure your garden looks full and colorful from May through October, the right companions make all the difference. This guide will help you select the best annuals, perennials, and herbs to grow alongside your dahlias for a vibrant, healthy garden.
By understanding the growth habits and needs of these summer favorites, you can create a balanced ecosystem that thrives with minimal fuss. We will look at visual pairings, functional plant partners, and the simple ways to keep everyone in your garden bed happy. If you want a deeper dive into dahlia companion plants, this is a great place to start.
The Benefits of Companion Planting with Dahlias
Dahlias are incredibly versatile, but they do have a specific growth cycle. They are often planted in late spring and take some time to reach their full, bushy glory. During those early months, a dahlia bed can look a little sparse. This is where companion planting shines. By surrounding your tubers with the right neighbors, you create a more finished look early in the season.
Beyond aesthetics, the right companions serve a functional purpose. Some plants act as a living mulch, keeping the soil cool and moist. Others serve as "trap crops," drawing aphids or beetles away from your precious blooms. Many companions also attract beneficial insects like ladybugs and lacewings, which act as a natural defense system for your garden.
Finally, companion planting allows you to extend your blooming window. While dahlias are the queens of August and September, many of their best partners start blooming in early summer. This ensures that your garden remains a destination for bees, butterflies, and your own enjoyment from the moment the frost leaves the ground until the first chill of autumn.
Simple Rules for a Successful Dahlia Garden
Before we dive into specific plant recommendations, it is helpful to remember a few basic principles. Success in the garden usually comes down to getting the environment right.
Match Your Sunlight and Soil
Dahlias are sun-worshippers. They need at least six to eight hours of direct sunlight every day to produce those massive, colorful flowers. When you choose companion plants, they must be able to handle that same level of sun. Similarly, dahlias require well-draining soil. They do not like to sit in "wet feet," which can cause the tubers to rot. Choose partners that thrive in similar conditions.
Give Them Space to Breathe
One of the most common mistakes is crowding plants too closely. Dahlias can grow quite large, with some varieties reaching four or five feet in height and three feet in width. They need good air circulation to prevent powdery mildew and other fungal issues. When planting companions, always check the mature width of both plants. Leave enough room so that as they grow, they aren't constantly fighting for physical space.
Feed the Hungry Neighbors
Dahlias are "heavy feeders." They use a lot of energy to create their lush foliage and huge flowers. If you plant them next to other aggressive, nutrient-hungry plants, they may struggle to get what they need. The best companions are those that are well-behaved and don't try to take over the entire root zone.
Key Takeaway: Focus on plants that share the same sun and water requirements as dahlias but offer different heights and textures to create a layered, professional look.
Best Perennial Companions for Dahlias
Perennials are the backbone of the garden. Once established, they come back year after year, providing a reliable structure for your seasonal dahlias. When choosing perennials, look for those that bloom at different times or offer high-contrast foliage.
Salvia (Meadow Sage)
Salvia is a fantastic partner for dahlias because of its vertical growth habit. Most salvias produce tall, slender spikes of flowers in shades of purple, blue, or red. These "cool" tones and upright shapes provide a perfect contrast to the round, heavy heads of dahlia blooms. Salvia is also a magnet for hummingbirds and butterflies, which adds movement and life to your garden beds.
Agastache (Hyssop)
Agastache is another pollinator powerhouse. It features minty-scented foliage and fuzzy flower spikes that last for weeks. Because it is relatively drought-tolerant once established, it won't mind the sunny, well-drained spot where your dahlias live. The airy texture of Agastache helps soften the look of the broader dahlia leaves.
Phlox (Garden Phlox)
Tall garden phlox offers large clusters of fragrant flowers that bloom in mid-to-late summer, right alongside your dahlias. If you choose varieties in shades of white or soft pink, they can act as a beautiful backdrop for more vibrantly colored dahlias. Phlox likes the same rich, moist soil that dahlias prefer, making them easy to care for together.
Artemisia
If you want a foliage-first companion, Artemisia is an excellent choice. Varieties like 'Silver Mound' or 'Powis Castle' provide shimmering silver leaves that make the bright colors of dahlias pop. Some gardeners find that the strong scent of Artemisia helps deter slugs and snails, which are known to nibble on young dahlia shoots.
Achillea (Yarrow)
Yarrow is a hardy, reliable perennial with flat-topped flower clusters and feathery foliage. The horizontal shape of the flowers creates a nice visual break from the rounded dahlia blooms. Yarrow is available in many colors, including bright yellows, deep reds, and soft pastels, so you can easily find a match for any dahlia variety.
Annual Flowers to Pair with Dahlias
Annuals are often the easiest way to experiment with color and texture. Since you plant them fresh each year, you can change your garden's look every season. Many annuals grow quickly and fill in the soil around the base of your dahlias.
Cosmos
Cosmos and dahlias are a classic garden pairing. Cosmos have a light, airy, and almost whimsical appearance with their delicate, fern-like foliage. They dance in the wind, providing a sense of movement that balances the sturdy, architectural stems of the dahlias. If you plant single-flowered cosmos, you will also provide an easy nectar source for bees.
Sweet Alyssum
Sweet Alyssum is a low-growing annual that forms a thick carpet of tiny, honey-scented white or purple flowers. It is the perfect "edging" plant for a dahlia bed. Because it stays low to the ground, it doesn't compete with the dahlias for sunlight, but it does a great job of covering the bare soil at the base of the taller plants. This keeps the ground cooler and helps suppress weeds.
Snapdragons
Snapdragons are wonderful for early-season color. They often start blooming well before the dahlias are ready to take center stage. By the time the dahlias are reaching their full height in mid-summer, the snapdragons provide a colorful mid-layer in the garden. They come in almost every color imaginable, allowing for endless design possibilities.
Nicotiana (Flowering Tobacco)
Most dahlias, while beautiful, do not have a strong scent. If you want a garden that smells as good as it looks, plant some Nicotiana nearby. These plants produce star-shaped flowers that release a heavenly fragrance, especially in the evening. Tall varieties like Nicotiana sylvestris can stand tall behind your dahlias, while shorter versions work well in the foreground.
Verbena bonariensis
This plant is often called "tall verbena," but it is so airy that you can see right through it. It produces small, purple flower clusters on wiry stems that can reach four feet tall. It is a favorite for many of us because it can be planted toward the front of a border without blocking the view of the plants behind it. It adds a magical, hazy purple mist to the dahlia bed.
Ornamental Grasses for Texture
Don't overlook the power of ornamental grasses. While they don't provide flashy flowers, they offer a level of texture and movement that no flowering plant can match. Grasses catch the light beautifully in the late afternoon and provide a sophisticated, modern look to your flower beds.
Pennisetum (Fountain Grass)
Fountain grass is loved for its soft, bottlebrush-like plumes that appear in late summer. The arching habit of the grass provides a soft "skirt" around the more rigid stems of the dahlias. Varieties like 'Hameln' stay compact and manageable, making them ideal for smaller garden spaces.
Miscanthus
For larger dahlia varieties, such as the massive Dinnerplate types, you may want a larger grass to match the scale. Miscanthus provides a tall, shimmering screen that looks spectacular when planted as a backdrop. In the autumn, the foliage turns golden or bronze, which perfectly complements the warm, autumnal tones of many dahlias.
Using Herbs as Functional Companions
Herbs are not just for the kitchen; they are fantastic garden companions that offer both beauty and protection. Many herbs have strong scents that can help confuse pests that are looking for a snack.
Nasturtium
Nasturtiums are perhaps the most famous companion for dahlias. They are often used as a "trap crop" for aphids. Aphids are highly attracted to nasturtiums and will often flock to them instead of your dahlias. This makes it easier to manage the pests in one spot. Plus, nasturtiums offer beautiful trailing foliage and bright, edible flowers in shades of orange, yellow, and red.
Cilantro and Anise
Cilantro and Anise both produce umbrella-shaped flowers (umbels) that are incredibly attractive to predatory wasps and hoverflies. While "wasps" might sound scary, these tiny beneficial insects are actually your best friends in the garden. They eat aphids, thrips, and other small pests that can damage dahlia leaves.
Basil
If you have a sunny spot near your dahlias, tucking in some basil can be very rewarding. Not only will you have fresh herbs for cooking, but the dark purple varieties of basil, like 'Crimson King', look stunning next to pink or white dahlias. The aromatic oils in the leaves may also help deter certain flying pests.
Key Takeaway: Herbs provide a "triple threat" in the dahlia garden: they look great, they provide food for your kitchen, and they help manage garden pests naturally.
Designing with Color and Form
When deciding what to plant with dahlias, it helps to think like a designer. You can go for a high-energy look with contrasting colors or a calming look with a monochromatic palette.
The Power of Contrast
If you are growing bold, orange dahlias, try pairing them with deep purple salvia or blue agastache. These colors sit opposite each other on the color wheel, making both of them appear more vivid. This high-contrast look is perfect for a sunny, energetic garden bed.
Soft and Sophisticated
For a more romantic feel, stick to a limited palette. Pair soft pink dahlias like 'Cafe au Lait' with white sweet alyssum and silver artemisia. This creates a dreamlike, "moon garden" effect that looks especially beautiful at dusk.
Mixing Shapes
Texture is just as important as color. Dahlias have very structured, solid blooms. Pair them with "filler" plants that have smaller, more delicate flowers or "spiky" plants that add height. Mixing these different forms ensures your garden looks interesting even when you aren't looking at it from a distance.
Creating a Cutting Garden Mix
Many gardeners grow dahlias specifically for bouquets. If your goal is to have plenty of flowers for the vase, you should plant companions that also make excellent cut flowers.
- Zinnias: These are the workhorses of the summer cutting garden. They come in a rainbow of colors and have sturdy stems that hold up well in water.
- Snapdragons: These add a much-needed "spike" shape to a bouquet, which contrasts beautifully with the round dahlia form.
- Ammi Majus (False Queen Anne’s Lace): This provides a delicate, lacy filler that makes any arrangement look professionally designed.
- Eucalyptus: Though often grown as an annual in many zones, eucalyptus provides incredible fragrant greenery that pairs perfectly with dahlias in a vase.
Caring for Your Mixed Garden Bed
Once you have your dahlias and their companions planted, the goal is to keep them healthy with the least amount of stress possible. At Longfield Gardens, we believe that gardening should be a joy, not a chore.
Deep Watering
Most of the plants mentioned in this guide prefer a "deep and infrequent" watering schedule. Instead of a light sprinkle every day, give the bed a thorough soaking once or truly twice a week, depending on the weather. This encourages the roots of both the dahlias and their companions to grow deep into the soil, making them more resilient during hot spells.
Mulching for Success
Applying a layer of organic mulch, such as shredded bark or compost, is one of the best things you can do for a mixed bed. Mulch helps hold moisture in the soil, suppresses weeds, and as it breaks down, it improves the soil structure. Just be sure to keep the mulch a few inches away from the base of the dahlia stems to prevent rot.
Deadheading
To keep your garden looking its best, take a few minutes each week to "deadhead" or remove spent blooms. For dahlias, this encourages the plant to keep producing new flowers. For many of their companions, like cosmos or zinnias, it prevents the plant from putting its energy into seed production, keeping the flower show going much longer.
What to Do Next:
- Choose a color theme for your dahlia bed (e.g., "Sunset Tones" or "Pastel Dreams").
- Select at least one tall companion for the back and one low companion for the front.
- Check your spacing to ensure everyone has room to grow.
- Enjoy the process of watching your garden evolve!
Conclusion
Creating a beautiful garden is about finding the right balance between your star players and their supporting cast. When you choose the right plants to grow with your dahlias, you aren't just making the garden prettier; you are creating a healthier environment for your flowers to thrive. Whether you choose the airy grace of cosmos, the vertical interest of salvia, or the protective qualities of nasturtiums, your dahlias will thank you with a spectacular display of color.
At Longfield Gardens, we love seeing how our customers combine their favorite varieties to create unique landscapes. Remember that gardening is an evolving journey. Don't be afraid to try a new combination this year—you might just find your new favorite pairing. For more inspiration, browse our Dahlia Dinnerplate Cafe Au Lait and our Dahlia Dinnerplate Cloud Nine Collection.
- Pair for sun and soil: Ensure all neighbors love the sun as much as dahlias do.
- Mix textures: Use grasses and airy annuals to balance heavy dahlia blooms.
- Include "helpers": Use herbs and trap crops to manage pests naturally.
"The most successful gardens are those where the plants support one another, creating a tapestry of color and life that changes every single day."
FAQ
What are the best low-growing plants for the front of a dahlia bed?
Sweet Alyssum and low-growing varieties of Nasturtium are excellent choices. They provide a "living mulch" that covers the soil and adds color without growing tall enough to block your view of the dahlia blooms.
Can I plant dahlias with vegetables?
Yes, dahlias grow very well near many vegetables. In fact, planting them near crops like tomatoes or peppers can help attract pollinators to your vegetable patch. Just ensure the vegetables don't shade out the dahlias, as they both need full sun.
Do I need to worry about companion plants taking nutrients from my dahlias?
Dahlias are heavy feeders, so it is important to choose companions that are not overly aggressive. Avoid invasive plants or those with very deep, greedy taproots. Providing a balanced fertilizer and plenty of compost at planting time will ensure there is enough food for everyone.
Will companion plants help prevent slugs from eating my dahlias?
Some plants, like Artemisia, have scents or textures that slugs find unappealing. While no plant is a 100% guarantee against pests, creating a diverse garden with many different types of foliage can make it much harder for slugs to settle in and cause significant damage.
