Table of Contents
- Introduction
- Why Dahlias Benefit from Companion Plants
- Choosing the Best Flowers to Plant with Dahlias
- Using "Trap Crops" to Protect Your Dahlias
- Herbs that Make Great Dahlia Neighbors
- Designing with Height and Structure
- Combining Dahlias with Perennials
- Dahlias in the Cutting Garden
- Managing Water and Fertilizer in Mixed Beds
- Growing Dahlias and Companions in Containers
- Understanding Timing and Your Zone
- Common Myths About Dahlia Companions
- Summary of Companion Planting Benefits
- Conclusion
- FAQ
Introduction
Planning a dahlia garden is one of the most exciting parts of the growing season. There is a special kind of magic in choosing the perfect combination of colors and shapes, from massive dinnerplate varieties to tidy ball dahlias. While these plants are stunning on their own, they often reach their full potential when paired with the right neighbors. At Longfield Gardens, we enjoy seeing how home gardeners use companion planting to create vibrant, healthy landscapes that bloom from midsummer all the way through the first frost.
Dahlias are excellent companion plants because they are versatile, sturdy, and visually striking. You can browse our Dahlias collection to explore the full range. In this guide, we will explore which plants thrive alongside dahlias, how to use companion planting to manage pests naturally, and how to design a garden bed that stays colorful even before the dahlias begin to bloom. Whether you are growing in a dedicated cutting garden or a mixed perennial border, choosing the right companions makes the process more rewarding.
Getting the most out of your garden comes down to understanding what your plants need to succeed. How to Plant Dahlias is a helpful place to start. By matching dahlias with partners that share their love for sun and water, you can create a low-maintenance and beautiful outdoor space.
Why Dahlias Benefit from Companion Plants
Dahlias are often the "stars" of the summer garden, but even stars need a supporting cast. Companion planting is the practice of placing different plants together so they can help each other grow. For dahlias, this support usually comes in three forms: pest management, aesthetic balance, and soil health.
Because dahlias grow from tubers and produce lush, green foliage, they can sometimes attract unwanted visitors like aphids or slugs. Certain companion plants act as natural deterrents, either by smelling unappealing to pests or by attracting "good bugs" that eat the "bad bugs." This helps keep your garden healthy without much extra effort. For more pairing ideas, see our companion planting guide for dahlias.
Aesthetically, dahlias can sometimes look a bit "leggy" at the base as they grow taller. Planting lower-growing flowers around their feet hides the bare stems and keeps the soil cool. Additionally, since dahlias don't typically start blooming until mid-to-late summer, early-season companions ensure your garden looks beautiful while you wait for those first dahlia buds to open.
Key Takeaway: Companion planting helps dahlias by repelling pests, hiding bare stems, and providing color throughout the entire growing season.
Choosing the Best Flowers to Plant with Dahlias
When picking neighbors for your dahlias, the most important rule is to match their growing conditions. All About Dahlias offers a helpful refresher on the basics. Dahlias love full sun (at least six hours a day), rich soil, and consistent moisture. Any plant you put next to them should enjoy those same things.
Zinnias for Continuous Color
Zinnias are perhaps the perfect partner for dahlias. They come in a rainbow of colors and have very similar needs. We find that zinnias are particularly helpful because they attract pollinators like butterflies and bees. They also attract predatory insects like ladybugs and hoverflies, which help keep aphid populations under control. Since both plants bloom heavily in late summer, they create a dense, colorful tapestry that is perfect for a cutting garden.
Marigolds for Pest Control
Marigolds are famous in the gardening world for their ability to protect their neighbors. They produce a scent that many garden pests find offensive, including aphids and certain types of beetles. Marigolds are generally shorter than most dahlia varieties, making them an excellent choice for the front of the border. They fill in the gaps at the base of your dahlias and provide a bright pop of orange or yellow that complements the deeper hues of many dahlia varieties.
Cosmos for Texture and Grace
If you want to add a light, airy feeling to your garden, cosmos are a wonderful choice. While dahlias are bold and structural, cosmos have feathery, delicate foliage and simple daisy-like blooms. They sway beautifully in the wind and add a sense of movement to the bed. Cosmos are also very easy to grow from seed and will bloom all summer long, providing a soft backdrop for your more dramatic dinnerplate dahlias.
Snapdragons for Early Season Interest
One common challenge with dahlias is that they take a while to get going. Snapdragons are cool-weather favorites that often start blooming much earlier in the summer. By the time the dahlias are reaching their full height in July and August, the snapdragons provide vertical interest and color at a mid-level height. Their spiked shape offers a great visual contrast to the rounded forms of dahlia flowers.
What to do next:
- Assess your garden's sun exposure to ensure it gets at least six hours of direct light.
- Pick 2–3 companion varieties that match your favorite dahlia colors.
- Plan to plant lower-growing companions like marigolds at the front edge of the bed.
- Leave enough space (about 18–24 inches) between dahlias and their companions to allow for air circulation.
Using "Trap Crops" to Protect Your Dahlias
Sometimes, the best way to protect a plant is to give the pests something else to eat. This is called "trap cropping." You plant something that pests love even more than your dahlias, drawing them away from your prize blooms.
Nasturtiums are the ultimate trap crop for dahlias. Aphids, which can sometimes be a nuisance for dahlia growers, find nasturtiums irresistible. By planting a border of nasturtiums nearby, you encourage the aphids to congregate there instead of on your dahlias. Nasturtiums are also beautiful, with round, lily-pad leaves and bright edible flowers.
Another helpful plant for pest management is Artemisia. This plant is grown mostly for its silvery, soft foliage rather than its flowers. Slugs and snails often dislike the scent and texture of Artemisia. Since slugs can be a challenge for young dahlia shoots in the spring, surrounding your planting area with Artemisia can act as a natural barrier.
Herbs that Make Great Dahlia Neighbors
You don't have to stick to flowers when choosing companions. Many common kitchen herbs are fantastic in the flower garden. Herbs often have strong scents that confuse or repel pests, and many of them produce tiny flowers that attract beneficial wasps and hoverflies.
- Anise and Cilantro: These herbs are excellent for attracting predatory insects. When these herbs are allowed to "bolt" (go to seed), they produce umbrella-shaped flower heads that are magnets for tiny wasps that hunt aphids.
- Lavender: Coastal lavender or traditional English lavender adds a wonderful fragrance to the garden. Its silvery-green foliage looks beautiful against the dark green leaves of the dahlia.
- Rosemary and Thyme: These hardy herbs can be planted as a low-growing border. Their woody stems and pungent oils help deter various crawling insects.
Key Takeaway: Fragrant herbs like lavender and cilantro do double duty by repelling pests and attracting beneficial insects to the garden.
Designing with Height and Structure
Dahlias can vary significantly in size, and ball dahlias are a good example of a form that fits neatly into mixed beds. Some dwarf varieties only grow 12 inches tall, while dinnerplate dahlias can easily reach five feet or more. To make your garden look its best, you should use the "layering" technique.
Background Plants
For tall dahlias, you need a backdrop that can hold its own. Canna lilies are a fantastic choice. They have large, tropical-looking leaves in shades of green, bronze, or even stripes. They love the same hot, sunny conditions as dahlias and provide a sturdy wall of foliage that makes the dahlia colors pop. Ornamental grasses, such as fountain grass, also make a great background. Their feathery plumes add texture and a "soft" look that balances the heavy, solid blooms of the dahlias.
Mid-Ground Fillers
This is where your dahlias will likely live. To fill in the spaces between them, consider plants like Salvia or Monarda (Bee Balm). These plants have a more "wild" and vertical growth habit that fills the gaps without crowding the dahlias. Salvia is particularly great because it is a favorite for hummingbirds, which are a joy to watch in the late summer garden.
Edging and "Spiller" Plants
To finish the look, you want something that covers the ground. Sweet Alyssum is a top recommendation for this. It grows in low, white or purple carpets and smells like honey. It is very effective at keeping the soil cool and moist around the dahlia tubers. Verbena is another great option for the edge of a bed or the side of a container. It has a trailing habit, so it will "spill" over the edges, softening the lines of your garden.
Combining Dahlias with Perennials
If you have a permanent perennial border, you can easily tuck dahlias into the gaps. This is a great way to keep the garden blooming after your spring and early summer perennials have finished their show.
Peonies and dahlias are a classic "relay race" pairing. Peonies bloom beautifully in late spring and early summer, but once their flowers are gone, the plant is mostly just green leaves. By planting dahlias near your peonies, the dahlias will take over the spotlight just as the peony flowers fade. The sturdy peony foliage can even help provide a little bit of wind protection for the growing dahlia stalks.
Phlox and Echinacea (Coneflowers) also work well. These are sturdy perennials that bloom around the same time as dahlias. They share a similar "prairie" or "cottage garden" aesthetic and are very attractive to butterflies. Because these perennials are hardy and return every year, they provide a reliable structure that you can plant your dahlia tubers around each spring.
What to do next:
- Identify "holes" in your perennial beds where summer color is lacking.
- Use tall plants like Canna lilies to create a "wall" behind your tallest dahlias.
- Plant Sweet Alyssum around the base of your dahlias to act as a living mulch.
- Ensure all companions are "well-behaved" and won't aggressively spread into the dahlia's root zone.
Dahlias in the Cutting Garden
Many people grow dahlias specifically for flower arrangements. If this is your goal, your companion planting strategy might be slightly different. You want to plant things that not only grow well together but also look great together in a vase.
Consider planting "filler" flowers that florists use to round out bouquets. Baby's Breath (Gypsophila) or flowering tobacco (Nicotiana) are excellent choices. Their small, airy blooms provide the perfect contrast to the large, bold "focal" flowers of the dahlia.
Another great cut-flower companion is the sunflower. While it might seem like they would compete, smaller "branching" sunflower varieties can be planted at the back of the dahlia bed. They provide long, sturdy stems for arrangements and share the dahlia's love for the sun. Just be sure to choose varieties that don't drop too much pollen if you plan to bring them inside!
Managing Water and Fertilizer in Mixed Beds
One thing to keep in mind when companion planting is that dahlias are "heavy feeders." This means they need a lot of nutrients and water to produce those big, beautiful blooms. When you add more plants to the bed, you are adding more "mouths to feed."
To keep everyone happy, we recommend focusing on the soil. Adding compost to your garden beds in the spring provides a slow-release source of nutrients that benefits all your plants. When it comes to watering, the best approach is "deep and infrequent." Instead of a light sprinkle every day, give the bed a good soak a few times a week. This encourages the roots of both the dahlias and their companions to grow deep into the soil, making them more resilient during hot spells.
Using a layer of mulch—or a "living mulch" like the Sweet Alyssum mentioned earlier—helps hold moisture in the soil. This is especially important for dahlias, as their tubers can be sensitive to getting too hot or drying out completely. For pinching and support tips, see our How to Pinch and Stake Dahlias.
Growing Dahlias and Companions in Containers
If you don't have a large garden plot, you can still enjoy companion planting in containers. If you want more container-specific ideas, take a look at What to Grow With Dahlias in Pots. Dahlias grow very well in pots, provided the pots are large enough (at least 12–15 inches in diameter for most varieties).
In a container, you can follow the "Thriller, Filler, Spiller" rule:
- Thriller: The dahlia is your star. Choose a variety that fits the size of your pot.
- Filler: Plant something like a zinnia or a small marigold around the dahlia to fill in the middle space.
- Spiller: Use Sweet Alyssum, Lobelia, or trailing Verbena to hang over the edges of the pot.
This creates a professional-looking arrangement that provides a full season of beauty. Just remember that container plants dry out faster than those in the ground, so you may need to water your dahlia pots daily during the height of summer.
Key Takeaway: Large containers are perfect for mini-companion gardens using the "thriller, filler, spiller" method to create a lush, full look.
Understanding Timing and Your Zone
While dahlias are generally easy to grow, their success often depends on timing. At Longfield Gardens, we ship our tubers based on your USDA hardiness zone so they arrive at the right time for planting. See our Shipping Information for details.
In most parts of the US, you should wait to plant your dahlias and their companions until the danger of frost has passed and the soil has warmed up to about 60°F.
If you live in a colder zone (Zones 3–7), your dahlias will be treated as annuals, meaning you’ll need to dig up the tubers in the fall if you want to save them for next year. However, many of their companions, like marigolds and zinnias, are true annuals that you will replant each spring anyway. This makes the "reset" of your garden bed each year an opportunity to try new color combinations and plant pairings!
Common Myths About Dahlia Companions
There are a few myths floating around the internet about what you should or shouldn't plant with dahlias. Let's clear a few of those up with simple facts.
Myth: You shouldn't plant dahlias near vegetables. Fact: Dahlias are actually great in the vegetable garden! They attract pollinators that help your tomatoes and squash produce more fruit. Just make sure the dahlias aren't so tall that they shade out your sun-loving vegetables.
Myth: Companion plants will "steal" all the nutrients from dahlias. Fact: As long as you provide healthy soil and regular water, there is plenty of room for everyone. In fact, some companions (like certain herbs) can actually improve the soil by attracting beneficial soil organisms.
Myth: You need a complex "guild" of 10+ plants for it to work. Fact: Simplicity is often better. Even just adding one type of companion, like a border of marigolds, can make a noticeable difference in the health and beauty of your dahlias.
Summary of Companion Planting Benefits
To make your dahlia garden the best it can be, keep these simple benefits in mind:
- Pest Control: Use marigolds and nasturtiums to keep aphids and beetles away.
- Soil Health: Use low-growing plants like alyssum to shade the soil and retain moisture.
- Extended Season: Use snapdragons or peonies to provide color before the dahlias bloom.
- Aesthetic Appeal: Use grasses and airy flowers like cosmos to add texture and movement.
Creating a mixed garden bed is a rewarding way to spend your time outdoors. By following these simple rules, you can ensure your dahlias have the support they need to thrive. Everything you need is backed by our 100% quality guarantee.
Conclusion
Dahlias are truly one of the most rewarding flowers you can grow, offering a spectacular display of color and form. By choosing the right companion plants, you aren't just making your garden prettier—you are creating a healthier, more balanced environment for your plants. From the pest-repelling power of marigolds to the airy beauty of cosmos, there is a perfect partner for every dahlia variety.
We believe that gardening should be a joy, not a chore. Using these simple companion planting techniques helps you work with nature rather than against it. Whether you are planting a few tubers in a pot or a whole row in a cutting garden, the right neighbors make all the difference.
"A well-planned garden is more than just a collection of plants; it's a small ecosystem where every flower plays a part in supporting the beauty of the whole."
For the best results this season, we recommend starting with high-quality tubers and a few packets of companion seeds. Visit us at Longfield Gardens to find your favorite varieties and start planning your most beautiful garden yet.
FAQ
Can I plant dahlias next to roses?
Yes, dahlias and roses can be excellent companions. They both love full sun and rich, well-drained soil. Since roses often have their biggest bloom flush in early summer and dahlias bloom in late summer and fall, planting them together ensures your garden stays colorful for many months. Just be sure to give each plant enough space so they don't compete for airflow, which helps prevent mildew.
What is the best plant to hide "ugly" dahlia legs?
Lower-growing annuals like Sweet Alyssum, Marigolds, or dwarf Zinnias are the best choices for hiding the bare lower stems of tall dahlia plants. These "filler" plants create a lush carpet of color at the base of the bed while keeping the soil cool and moist for the dahlia tubers.
Do dahlias attract pollinators to my other plants?
Absolutely! Dahlias—especially the single-flowered varieties where the center is visible—are fantastic for attracting bees, butterflies, and even hummingbirds. By planting dahlias, you are inviting beneficial insects into your yard that will also help pollinate your vegetables and other flowering plants.
Is it okay to plant dahlias in a vegetable garden?
Yes, dahlias are a wonderful addition to a vegetable garden. They provide a splash of color and attract pollinators that can increase the yield of crops like beans, tomatoes, and cucumbers. Many gardeners plant a row of dahlias along the edge of their vegetable patch to serve as a cutting garden while helping the local ecosystem.