Table of Contents
- Introduction
- Understanding the Needs of Your Dahlias
- Best Flowering Companions for Late Summer Color
- Low-Growing Plants for the "Feet" of Dahlias
- Fillers for Early Season Interest
- Adding Texture with Foliage and Grasses
- Herbs as Functional Companions
- Design Tips: Color and Height Management
- Growing Dahlias in Containers
- Practical Care for Mixed Beds
- Conclusion
- FAQ
Introduction
There is nothing quite like the feeling of watching your first dinnerplate dahlia of the season unfurl its petals. Whether it is a massive dinnerplate variety the size of a dinner plate or a perfectly symmetrical pompon, these flowers bring a sense of pure joy and accomplishment to any garden. At Longfield Gardens, we know that while dahlias are spectacular on their own, they truly shine when surrounded by the right neighbors.
This guide is designed for home gardeners who want to move beyond the traditional "dahlia row" and create a lush, layered landscape. We will explore the best flowers, foliage, and herbs to pair with your dahlias to ensure your garden looks beautiful from early summer through the first frost. By choosing the right companion plants, you can enhance your garden’s color palette, improve soil health, and even manage common garden visitors naturally.
Successful companion planting starts with understanding what a dahlia needs to thrive and matching it with plants that share those requirements.
Understanding the Needs of Your Dahlias
Before choosing companion plants, it is helpful to look at what dahlias require to stay healthy and productive. Dahlias are sun-loving plants that thrive when they have plenty of room to breathe. Most varieties need at least six to eight hours of direct sunlight every day. They are also known as "heavy feeders," which simply means they use a lot of nutrients and water to produce those famous, oversized blooms. For timing and climate questions, our Hardiness Zone Map can help you plan ahead.
Drainage is another essential factor. Drainage refers to how quickly water moves through the soil. Dahlias prefer soil that stays moist but never soggy. If the soil stays too wet for too long, the tubers can struggle. Because of these needs, the best companions are plants that also enjoy the sun and won't compete too aggressively for the "dinner" provided by your compost and fertilizer.
The growth habit of the dahlia is also important for planning. Most dahlias start as small sprouts in late spring and grow into large, bushy plants by August. This means you have a "gap" in the garden during May and June. Using companions to fill this gap is one of the smartest ways to keep your garden looking full all season long.
Key Takeaway: Match your dahlias with plants that love full sun and well-drained soil. Choose neighbors that won't crowd the dahlia's root zone, as dahlias need their space to reach full potential.
Best Flowering Companions for Late Summer Color
When your dahlias begin to hit their stride in July and August, you want companions that can keep up with their energy. These flowering plants provide a beautiful backdrop or a contrasting shape to the bold dahlia blooms. If you want more inspiration, see our guide to what plants look good with dahlias.
Cosmos: The Classic Partner
Cosmos are perhaps the most popular companion for dahlias. They have airy, fern-like foliage that provides a soft texture contrast to the broad, heavy leaves of the dahlia. Because cosmos are tall and somewhat "see-through," they don't block the light or airflow.
We often recommend planting single-flowered cosmos varieties. They attract pollinators like bees and butterflies, which are essential for a healthy garden ecosystem. Varieties in shades of pink, white, and burgundy create a romantic, cottage-garden look when woven between dahlia stems.
Zinnias: Bold and Bright
If you love a "hot" color palette—think bright oranges, fiery reds, and sunny yellows—zinnias are the perfect match. Like dahlias, zinnias are sun-worshippers and bloom right up until the frost. For a deeper dive into design ideas, our article on companion planting with dahlias covers this theme in more detail.
Zinnias are excellent for cutting gardens. If you are growing dahlias for bouquets, having zinnias nearby provides smaller, rounded shapes to complement the larger dahlia forms. Since both plants are susceptible to similar leaf issues like powdery mildew, make sure to leave enough space between them for air to circulate freely.
Salvia: Vertical Interest
Most dahlias have a rounded or mounded growth habit. To make your garden beds more visually interesting, it helps to add "spikes." Salvia provides tall, slender wands of color that stand upright.
Blue and purple salvias look stunning next to yellow or orange dahlias because they are "complementary colors" (colors that sit opposite each other on the color wheel). Salvia is also a favorite for hummingbirds, which helps bring even more life and movement to your yard.
What to do next:
- Identify the tallest dahlia varieties in your garden.
- Place cosmos or salvia behind or between these tall dahlias.
- Ensure there is at least 12 to 18 inches of space between the base of each plant.
- Deadhead (remove spent blooms) from both the companions and the dahlias to keep the colors coming.
Low-Growing Plants for the "Feet" of Dahlias
Tall dahlias can sometimes look a bit "leggy" at the bottom. As the plant focuses its energy on top-heavy blooms, the lower stems can become bare. Low-growing companions act as a living mulch, shading the soil and hiding those bare stems. If you are looking for front-of-border ideas, check our companion plants for the front of dahlias.
Sweet Alyssum
Sweet Alyssum is a fantastic ground cover. It grows in low, honey-scented mounds that spill over the edges of garden beds. Because its root system is shallow, it won't steal too many nutrients from your dahlia tubers. The white or purple carpets of alyssum keep the soil cooler and help retain moisture, which dahlias appreciate during the heat of July.
Nasturtiums
Nasturtiums are versatile plants that come in both mounding and trailing varieties. They are famous for being "trap crops." This means they often attract aphids away from your more prized plants. While it might sound strange to want a plant that attracts pests, it is a simple way to keep your dahlias cleaner without using harsh sprays. Plus, both the leaves and flowers of nasturtiums are edible and add a peppery kick to summer salads.
Heliotrope
If you want to add fragrance to your garden, heliotrope is a lovely choice. It produces deep purple clusters of flowers that smell like vanilla or cherry pie. It stays relatively low and enjoys the same consistent moisture that dahlias do. The dark, textured leaves provide a beautiful contrast to the lighter green dahlia foliage.
Fillers for Early Season Interest
One of the most common questions we hear at Longfield Gardens is what to do with the empty space while waiting for dahlias to grow. Dahlias are late starters, often not reaching their full size until mid-summer. You can use early-season bloomers to keep the garden pretty while the dahlias are still just green shoots. For broader seasonal planning, our dahlia companion planting guide is a helpful next step.
Snapdragons
Snapdragons love the cooler weather of late spring and early summer. By the time the summer heat arrives and the dahlias are ready to take over, the snapdragons have usually finished their first big flush of flowers. They are easy to tuck into the gaps between your dahlia tubers. As the dahlias grow tall, they will eventually cover the space where the snapdragons were.
California Poppies
These are cheerful, easy-to-grow annuals that provide bright pops of color early in the year. They have fine, bluish-green foliage that looks beautiful next to the emerging dahlia sprouts. Because they are relatively short-lived, they won't compete with the dahlias once the "big show" begins in August.
Pansies and Violas
For a very early start, pansies are the go-to choice. They can handle a light frost and will bloom happily while your dahlia tubers are just beginning to wake up in the warm soil. Once the weather gets hot, pansies usually fade, which is perfectly timed for the dahlias to expand and fill the space.
Key Takeaway: Use "gap-filler" plants like snapdragons and poppies to enjoy color in your garden during the weeks when dahlias are still putting on their initial leafy growth.
Adding Texture with Foliage and Grasses
A professional-looking garden isn't just about flowers; it is about texture. Adding plants with interesting leaves or swaying stems makes the bold dahlia blooms stand out even more.
Ornamental Grasses
Grasses like Pennisetum (fountain grass) add a sense of movement to the garden. When the wind blows, the soft plumes and slender blades of grass dance around the sturdy, static dahlia flowers. This contrast makes the garden feel more dynamic. Grasses are also wonderful for fall interest, staying attractive even after the first light frost turns the dahlia foliage brown.
Dusty Miller
Dusty Miller is grown for its silvery-white, velvety leaves. This "cool" color provides a rest for the eyes in a garden filled with hot, saturated dahlia colors. It stays fairly compact, making it an excellent edging plant for a dahlia border. The silver foliage looks especially striking at night, catching the moonlight and making the garden glow.
Artemisia
Similar to Dusty Miller, Artemisia offers silver or gray-green foliage. Some varieties, like Powis Castle, grow into soft, billowing mounds. These plants are often avoided by slugs and snails, which can sometimes be a nuisance for young dahlias. Planting a border of Artemisia can act as a natural deterrent while looking incredibly elegant.
Herbs as Functional Companions
Many gardeners forget that herbs make excellent companions for flowering bulbs and tubers. Many herbs have strong scents that can help mask the scent of plants that certain insects like to snack on. If you want to keep growing with confidence, Longfield Gardens also offers helpful service and support, plus a 100% guarantee on the quality of what you buy.
Anise and Cilantro
These herbs produce delicate, umbrella-shaped flowers (called umbels) that are a magnet for beneficial insects. Predatory wasps and hoverflies love these flowers, and they happen to be the natural "cleanup crew" for garden pests. Anise, in particular, has a lovely licorice scent and feathery leaves that look beautiful tucked behind smaller dahlia varieties.
Basil
If you have a sunny spot, basil is a great neighbor for dahlias. It enjoys the same heat and water schedule. While you are out picking dahlias for a vase, you can grab a few handfuls of basil for dinner. The deep purple varieties of basil, like 'Dark Opal,' look stunning when paired with pink or white dahlias.
What to do next:
- Mix a few herbs into your flower borders rather than keeping them in a separate "herb garden."
- Let a few of your herbs go to flower to attract helpful insects.
- Ensure your herbs have enough sun; most won't thrive in the shade of a 5-foot-tall dinnerplate dahlia.
Design Tips: Color and Height Management
Designing a garden with dahlias is like directing a play. You have your stars (the dahlias) and your supporting cast (the companions). To get the best look, you need to manage the "stage" carefully.
Consider the Height
Always check the expected height of your dahlia variety. A tall variety like Kelvin Floodlight can easily reach 4 or 5 feet, while "border" or "gallery" dahlias might only grow 12 to 18 inches tall.
- Tall Dahlias: Place these at the back of the bed. Use airy companions like Verbena bonariensis or tall ornamental grasses to weave through them.
- Medium Dahlias: These are the workhorses of the garden. Pair them with zinnias, salvia, or dusty miller.
- Short Dahlias: Use these at the front of the border with ground covers like sweet alyssum or mounding nasturtiums.
Playing with Color
Color is the most fun part of companion planting. You can choose a monochromatic look, where you use different shades of the same color (for example, white dahlias with white alyssum and silver dusty miller). This creates a very calm, sophisticated feel.
Alternatively, try complementary colors. Orange dahlias with purple salvia or blue sea holly (Eryngium) make both colors pop and appear more vivid. If you aren't sure where to start, a "sunset" mix of yellows, oranges, and pinks is always a winner in a late-summer garden.
Growing Dahlias in Containers
If you have a small patio or balcony, you can still enjoy the beauty of dahlias. Growing them in pots requires a bit more attention to watering, but it allows for some beautiful combinations.
When planting in a container, use the "Thriller, Filler, Spiller" method:
- The Thriller: This is your dahlia. Choose a mid-sized or dwarf variety so it doesn't become too top-heavy for the pot.
- The Filler: Add a plant with interesting foliage or smaller flowers, like a compact zinnia or a small mounded herb.
- The Spiller: Choose a plant that will hang over the edge of the pot, like trailing nasturtiums or creeping Jenny.
Keep in mind that containers dry out faster than the ground. Because both the dahlia and its companions are sharing a limited amount of soil, you will need to feed them regularly with a balanced liquid fertilizer to keep them blooming.
Practical Care for Mixed Beds
To keep your mixed garden beds healthy, a few simple habits make a big difference. At Longfield Gardens, we believe that getting the basics right is the easiest way to ensure gardening success. If you need order help, our shipping information page explains how we time deliveries by zone.
Watering Correctly
Dahlias like deep watering. Instead of a light sprinkle every day, give the garden a thorough soak a few times a week. This encourages the roots to grow deep into the soil. When you have companion plants, try to water at the base of the plants rather than over the leaves. This helps prevent leaf diseases and ensures the water gets exactly where it's needed—the roots.
Providing Support
Many dahlias need staking because their blooms are so heavy. If you are using companion plants, you can often hide your stakes behind the taller companions. For example, a tall cosmos plant can easily camouflage a bamboo stake or a tomato cage used to support a dahlia.
Feeding the Soil
Since you are growing multiple plants in one area, the soil is working hard. Adding a layer of compost in the spring before planting is a great way to start. Throughout the summer, a fertilizer high in phosphorus will help encourage more blooms rather than just more green leaves.
Key Takeaway: Deep watering and regular feeding are essential when growing dahlias with companions, as they are all sharing the same resources in the soil.
Conclusion
Creating a garden filled with dahlias and their perfect companions is a rewarding journey that brings beauty to your home and joy to your neighborhood. By selecting plants that share the same love for sun and well-drained soil, you can build a vibrant, healthy ecosystem. Whether you choose the airy grace of cosmos, the functional benefits of nasturtiums, or the silver shimmer of dusty miller, your dahlias will have the support they need to truly shine.
- Start with sun-loving companions like Zinnias and Cosmos.
- Use ground covers like Sweet Alyssum to shade the soil.
- Incorporate herbs to attract beneficial insects.
- Plan for early-season color with snapdragons or pansies.
At Longfield Gardens, we are here to help you grow your most beautiful garden yet. With a little planning and the right neighbors, your dahlias will be the stars of the season, providing you with endless bouquets and a stunning outdoor retreat.
"A well-planned garden isn't just about the flowers; it's about the relationships between the plants that make the whole space thrive."
FAQ
Can I plant dahlias and zinnias together?
Yes, zinnias and dahlias make excellent companions because they both love full sun and bloom at the same time. Just ensure you leave enough space between them—usually 12 to 18 inches—to allow for good airflow, which helps prevent powdery mildew on their leaves.
What can I plant to hide the bare stems of my dahlias?
Low-growing "ground cover" plants are best for this. Sweet Alyssum, mounding Nasturtiums, and Dusty Miller are all great choices. These plants stay short and bushy, creating a "skirt" around the taller, more leggy dahlia stems.
Do companion plants steal nutrients from dahlias?
Dahlias are heavy feeders, so they do need plenty of nutrients. However, as long as you provide regular fertilizer and start with healthy, compost-rich soil, there is usually plenty for everyone. Avoid planting "aggressive" spreaders like mint or invasive vines, which can overwhelm the dahlia’s root zone.
What are the best flowers for a cutting garden with dahlias?
If you want to create beautiful bouquets, plant flowers that offer different shapes. Snapdragons and Salvia provide "spikes," while Cosmos and Queen Anne’s Lace provide "filler" and texture. This variety will make your dahlia-focused arrangements look professional and balanced.