Introduction
There is nothing quite like the excitement of seeing the first dahlia buds unfurl in mid-summer. Whether you love the massive, pillowy petals of dinnerplate varieties like Cafe au Lait or the intricate, geometric shapes of pompon dahlias, these plants are the undisputed stars of the late-season garden. At Longfield Gardens, we enjoy helping you find the perfect combinations to make these showstoppers shine even brighter from the moment they are planted until the first frost.
This guide is for any gardener who wants to create a lush, professional-looking flower bed by surrounding their dahlias with the right companions. We will cover which plants provide early-season interest while your dahlias are still growing, which neighbors help with natural pest control, and how to choose partners that won't compete for nutrients.
By choosing the right companions, you can ensure your garden stays colorful and healthy all season long. Gardening is a rewarding way to express your creativity, and mixing different plants is one of the easiest ways to achieve a stunning result.
Why Companion Planting Matters for Dahlias
Dahlias are spectacular, but they are also "heavy feeders." This means they require plenty of nutrients and water to produce those famous, large blooms. Because they grow from tubers planted in late spring, there is often a gap of several weeks where the soil looks a bit bare. Choosing the right neighbors helps fill this space with color while the dahlias establish themselves.
Another reason to consider companion plants is what we call "dahlia legs." As dahlia plants grow tall, the bottom of the stalks can sometimes look a bit sparse or leafy. Planting lower-growing flowers in front of them acts as a beautiful screen, hiding the base of the stalks and creating a full, tiered look in your garden beds.
Finally, the right companions can provide a helping hand with garden health. Some plants attract beneficial insects that keep common garden pests in check, while others have scents that naturally discourage unwanted visitors. When you choose plants that share the same love for sunshine and well-drained soil, you create a mini-ecosystem where everything can thrive together.
Matching Needs: The "Right Plant, Right Place" Rule
Before picking out specific flowers, it is important to remember the basic needs of a dahlia. To get the best results, you must match your companion plants to the environment where dahlias grow best.
- Sunlight: Dahlias need full sun, which means at least six to eight hours of direct light every day. Any plant you put next to them must also enjoy a sunny spot.
- Drainage: "Drainage" is simply how fast water leaves the soil. Dahlias do not like "wet feet," meaning their tubers can rot if they sit in soggy ground. Their neighbors should also prefer well-drained soil.
- Space: Dahlias need room for air to circulate around their leaves. This helps keep the foliage dry and healthy. When planting companions, we recommend leaving enough space so the plants aren't touching until they are fully grown.
Key Takeaway: Always pair dahlias with plants that thrive in full sun and well-drained soil. Avoid "thirsty" plants that require constant soaking, as this can lead to issues for the dahlia tubers.
Best Flowers for Early Season Color
Since dahlias don't usually start their big show until July or August, many gardeners use early-season bloomers to keep the garden looking bright in May and June. These plants do their best work while the dahlias are still sending up their first green shoots.
Snapdragons
Snapdragons are a fantastic choice because they love the cooler weather of late spring and early summer. By the time the summer heat really kicks in and the dahlias begin to take over, snapdragons are often ready for a break. They come in almost every color imaginable, allowing you to coordinate with your future dahlia blooms.
Sweet Alyssum
Sweet alyssum is a low-growing plant that looks like a carpet of tiny white or purple flowers. It smells wonderful—often like honey—and fills in the bare soil around the base of your dahlias quickly. Because it stays low to the ground, it won't compete with the dahlias for sunlight. For more design ideas, see what plants grow well with dahlias.
Pansies and Violas
If you plant your dahlia tubers and find the garden looks a little empty, tucking in some pansies or violas provides instant cheer. They are small enough to be moved or tucked away if the dahlias need more space later in the summer.
Low-Growing Companions to Cover "Dahlia Legs"
As dahlias reach their full height—which can be anywhere from three to five feet for many varieties—the bottom third of the plant can look a bit plain. We like to use "understory" plants to fill this gap.
Dusty Miller
With its silvery-grey, velvety leaves, Dusty Miller provides a beautiful neutral backdrop for bright dahlia colors. It rarely grows taller than 12 to 18 inches, making it the perfect height to sit right in front of your taller dahlia varieties. The cool silver tones make the hot pinks, oranges, and reds of dahlias like 'Thomas Edison' or 'Cornel' really pop.
French Marigolds
French marigolds are sturdy, cheerful, and stay relatively short. They are excellent for the front of a border. They also have a distinct scent that many gardeners find helpful for keeping the garden environment balanced.
Geraniums (Pelargoniums)
The classic garden geranium is a sun-lover that produces bold clusters of flowers. They are drought-tolerant once established, meaning they won't demand more water than your dahlias can handle. Their mounded shape is perfect for hiding the base of dahlia stakes.
Airy Partners for Texture and Movement
Dahlias have very solid, heavy blooms. To make your garden feel more graceful and less "stiff," it helps to plant "airy" companions. These are plants with thin stems and small flowers that dance in the breeze.
Cosmos
Cosmos are perhaps the most popular companion for dahlias. They have feathery, fern-like foliage that adds a soft texture to the garden. Varieties like 'Sensation Mix' offer shades of pink, white, and maroon that look lovely alongside dahlia blooms. Because cosmos are also great for cutting, they are a natural fit if you are growing a cutting garden.
Verbena bonariensis
This plant is a favorite at Longfield Gardens because of its unique habit. It grows tall (up to 4 feet) but is very "see-through." It features clusters of tiny purple flowers on wiry stems. You can actually plant this in front of dahlias, and you will still be able to see the dahlias through the purple haze of the Verbena. It adds wonderful movement to the garden.
Ornamental Grasses
Grasses like Pennisetum (fountain grass) provide a beautiful contrast to the broad leaves of dahlia plants. The fine texture of the grass blades and the fuzzy flower heads that appear in late summer create a sophisticated, natural look.
What to do next:
- Identify the tallest dahlia varieties in your garden.
- Plan to place "airy" plants like Cosmos or Verbena between or just behind them.
- Use "filler" plants like Dusty Miller in the front row to create a layered effect.
Natural Pest Control and Pollinator Support
A healthy garden is a busy garden. By planting flowers that attract bees, butterflies, and other helpful insects, you can help your dahlias stay healthy.
Salvia
Perennial salvias, such as May Night, are pollinator magnets. Their spiked flowers provide a different shape compared to the round dahlia blooms, and they attract bees and hummingbirds. Keeping pollinators in your garden is essential for a vibrant landscape.
Nasturtiums
Nasturtiums are often used as a "trap crop." This means they are very attractive to aphids. Many gardeners plant nasturtiums a short distance away from their dahlias to draw aphids away from their prized flowers. Nasturtiums are easy to grow from seed and have beautiful, edible flowers and lily-pad-shaped leaves.
Anise Hyssop
This herb has licorice-scented leaves and beautiful purple flower spikes. It is famous for attracting butterflies and beneficial wasps that help control common garden pests. It is a tough plant that handles the heat of summer just as well as dahlias do.
Designing with Color and Form
When choosing what to plant next to your dahlias, thinking about color combinations can take your garden from good to great.
The Monochromatic Look
For a sophisticated feel, try a monochromatic palette. If you are growing white dahlias like Boom Boom White or 'Snow Country,' pair them with white sweet alyssum and silvery Dusty Miller. This creates a "moon garden" effect that glows at dusk.
Complementary Colors
If you want high energy, use complementary colors (colors opposite each other on the color wheel). Pair deep purple dahlias with bright yellow flowers like Coreopsis or yellow Marigolds. The contrast makes both colors appear more vivid.
Hot Tones
Dahlias excel in "hot" colors—fiery reds, oranges, and yellows. Pair a variety like Kelvin Floodlight (yellow) with red Salvias or orange Zinnias for a tropical, high-summer vibe.
Tips for Planting and Spacing
One of the most common mistakes is planting companions too close to the dahlia tuber. Remember that a dahlia tuber will grow into a large, bushy plant.
- Give the Tuber Space: When you plant your dahlia tuber, mark the spot with a stake. Avoid planting anything else within 12 to 18 inches of that stake. This ensures the dahlia has enough room to grow and that the soil doesn't get too packed down around the tuber.
- Staking Early: It is much easier to put your dahlia stakes in the ground at planting time. This also helps you see where the "star of the show" will be, so you can arrange your companion plants around it.
- Watering Correctly: Most dahlia companions like to dry out slightly between waterings. When you water, try to aim for the base of the plants rather than spraying the leaves. This keeps the foliage dry and reduces the chance of mildew.
- Feeding Your Garden: Since dahlias are heavy feeders, they will appreciate a boost of fertilizer during the growing season. Their companions will often benefit from this as well, but be careful not to over-fertilize low-maintenance plants like nasturtiums, which might produce more leaves than flowers if given too much food.
Using Herbs as Companions
Herbs aren't just for the kitchen; they make excellent garden companions. Many herbs have strong scents and interesting textures that complement dahlias perfectly. For zone and planting guidance, check Hardiness Zone Map.
- Lavender: The grey-green foliage of lavender stays attractive all year. It thrives in the same sunny, well-drained conditions as dahlias and provides a lovely scent.
- Cilantro and Dill: If you let these herbs "bolt" (go to seed), they produce delicate, umbrella-shaped flowers. These flowers are highly attractive to beneficial insects like hoverflies, which are great to have around your dahlias.
- Rosemary: For larger dahlia beds, a rosemary bush can provide a sturdy, evergreen anchor. Its needle-like leaves offer a sharp contrast to the soft, broad leaves of the dahlia.
Growing Dahlias and Companions in Containers
If you have a small space, you can still enjoy dahlia companion planting. Large pots are best for this, as dahlias need plenty of root room.
For a successful "thriller, filler, spiller" container:
- The Thriller: A medium-sized dahlia (look for "border" or "gallery" varieties).
- The Filler: Plants like Dusty Miller or Heliotrope to add bulk and color around the middle.
- The Spiller: Trailing plants like Bacopa or creeping zinnia (Sanvitalia) to hang over the edges of the pot.
Ensure your container has large drainage holes. We recommend using a high-quality potting mix that stays light and airy. Because containers dry out faster than garden beds, you will need to check the moisture level more often, especially during the peak of summer. If you want more container-specific ideas, see what can I plant with dahlias in pots.
Conclusion
Creating a garden with dahlias and their companions is one of the most enjoyable parts of the growing season. By choosing neighbors that share the same love for sun and well-drained soil, you can build a landscape that is both beautiful and resilient. Whether you are using sweet alyssum to cover the ground or airy cosmos to add movement, these combinations help your dahlias truly shine.
- Choose companions that share dahlia's sun and soil needs.
- Use low-growing plants to hide the base of tall dahlia stalks.
- Incorporate "airy" textures to balance the heavy blooms of the dahlias.
- Plant for pollinators to keep your garden ecosystem healthy.
At Longfield Gardens, we believe that gardening should be a simple, joyful experience. We provide the quality bulbs and plants you need to get started, and we stand behind them with our quality guarantee. The next step is yours—pick your favorite colors, grab a trowel, and start planting your own stunning dahlia display!
"The secret to a stunning dahlia bed isn't just the dahlias themselves, but the supporting cast of plants that fill the gaps, hide the stalks, and bring the whole garden to life with color and texture."
FAQ
Can I plant dahlias next to roses?
Yes, you can plant dahlias next to roses as long as both plants have enough space to breathe. Roses and dahlias both love sun and rich soil, but they can be susceptible to some of the same leaf issues if they are crowded. Ensure there is plenty of air circulation between the rose bush and your dahlia plants to keep them both healthy. For more mixed-bed ideas, see can you plant dahlias with roses.
Will companion plants take away nutrients from my dahlias?
Dahlias are heavy feeders, so they do need a lot of nutrients. However, as long as you provide regular fertilizer and don't plant aggressive, invasive species right on top of the dahlia tubers, they will coexist happily. Choosing light-feeding companions like cosmos or alyssum is a great way to ensure the dahlias get everything they need.
What is the best plant to stop pests on dahlias?
While no plant is 100% pest-proof, nasturtiums are excellent "trap crops" that draw aphids away from your dahlias. Herbs like Anise Hyssop and flowers like Salvia attract predatory insects that eat common pests. Surrounding your bed with these plants creates a more balanced environment that naturally keeps pest levels lower.
When should I plant my companion plants?
If you are using annuals like snapdragons or alyssum, you can plant them at the same time you plant your dahlia tubers in late spring. This allows them to start growing while the dahlias are still underground. For perennials like Lavender or Salvia, you can plant them whenever the soil is workable in the spring or fall.
