Introduction
There is a special kind of magic that happens in the garden when the first dahlia of the season unfurls its petals. Whether it is a dinnerplate variety the size of a frisbee or a dainty pompon, these flowers bring a level of color and geometric perfection that is hard to find anywhere else. At Longfield Gardens, we see every spring as an opportunity to help home gardeners discover the joy of growing these spectacular summer bloomers.
If you are new to the world of dahlias, you might find yourself wondering about the best way to get started. You may have heard some gardeners talking about planting dahlia "bulbs" while others are busy starting dahlia seeds in little trays on their windowsills. This leads to a very common question for beginners: do dahlias have seeds or bulbs?
The answer is actually both, but with a few important distinctions that will change how you plan your garden. This post covers the differences between dahlia seeds and tubers, why you might choose one over the other, and how to successfully grow them for a season full of blooms. Whether you want a specific, reliable color or a garden full of surprises, understanding these two methods is the first step toward dahlia success.
Do Dahlias Have Seeds or Bulbs?
When you look at a dahlia plant, it can be a bit confusing to figure out how it started. Technically, dahlias do not have bulbs in the same way a tulip or a daffodil does. Instead, they grow from thickened, underground storage roots called tubers. These tubers look quite a bit like a bunch of sweet potatoes or fingerling potatoes clinging to a central stem.
While most people refer to them as bulbs for simplicity, the distinction matters because of how they grow. A true bulb, like an onion, is made of layers of modified leaves. A tuber, however, is a solid mass of energy-storing tissue. This is the primary way dahlias are sold and shared among gardeners.
At the same time, dahlias also produce seeds. If you leave a flower on the plant after it has finished blooming, it will eventually form a seed pod. These seeds can be harvested, dried, and planted the following spring. So, the short answer is that dahlias produce both seeds and tubers, but they serve very different purposes for the home gardener.
Understanding Dahlia Tubers
For most gardeners, tubers are the gold standard for planting. If you have ever walked through a botanical garden and fallen in love with a specific named variety—like the creamy 'Cafe au Lait' or the vibrant 'Cornel'—you are looking at a plant that was grown from a tuber.
Why Tubers Are Like Clones
The most important thing to know about dahlia tubers is that they are genetically identical to the parent plant. When we ship tubers from Longfield Gardens, we are providing you with a biological "clone." If you plant a tuber from a specific pink decorative dahlia, you are guaranteed to get that exact same pink decorative dahlia in your garden.
This reliability is why tubers are the preferred choice for people who are designing specific color palettes or want a predictable height and flower shape. When you buy a tuber, you know exactly what the plant will look like before it ever breaks the soil.
The Anatomy of a Healthy Tuber
A dahlia tuber needs three specific parts to be viable. It needs the body (the fleshy part that holds the food), the neck (the thin part connecting the body to the stem), and the "eye." The eye is the most critical piece; it is the small growth bud where the new sprout will emerge.
Eyes can be hard to see in early spring when the tubers are dormant. They look like tiny bumps, similar to the eyes on a potato. If a tuber is missing an eye, it will never sprout, even if the fleshy body looks perfectly healthy. This is why we carefully inspect every tuber to ensure it has the potential to grow into a beautiful, vigorous plant.
The Magic of Multiplication
One of the most rewarding parts of growing dahlias is that they are the gift that keeps on giving. When you plant one tuber in the spring, the plant spends the summer gathering energy from the sun. By the time the first frost hits in the autumn, that single tuber has usually grown into a large clump of multiple new tubers.
If you live in a warm climate, these can stay in the ground. In colder regions, you can dig up the clump, store it over the winter, and divide it in the spring. This allows you to turn one plant into five or six plants for the following season.
Understanding Dahlia Seeds
While tubers offer predictability, dahlia seeds offer adventure. Growing dahlias from seed is a completely different experience that appeals to gardeners who love variety and don't mind a little bit of the unknown.
Genetic Surprises
Unlike tubers, dahlia seeds are not "true to type." This is because dahlias are octoploids, meaning they have eight sets of chromosomes—far more than most plants. When a bee moves from one dahlia to another, it mixes up a massive amount of genetic information.
If you plant a seed from a 'Thomas Edison' dahlia, the resulting flower will almost certainly not look like 'Thomas Edison.' It might be a different color, a different size, or a different shape entirely. Every single dahlia grown from seed is a brand-new variety that has never existed before. For some gardeners, this "treasure hunt" is the most exciting part of the season.
Where Seeds Come From
If you want to find dahlia seeds, you have to look at the center of the flower. Dahlias are part of the Asteraceae family, which means their "flower" is actually a collection of many tiny flowers. The outer petals are called ray florets, and the center parts are called disc florets.
The disc florets are where the pollen and nectar live. Once these are pollinated by bees or butterflies, the petals fall away and the base of the flower swells into a seed pod. As the pod dries and turns brown, it fills with flat, dark, almond-shaped seeds.
Why Breeders Use Seeds
Professional dahlia breeders use seeds to create the next generation of famous flowers. They cross-pollinate specific plants, harvest the seeds, and grow thousands of seedlings in hopes of finding one "diamond in the rough" with a unique color or a stronger stem. If they find a seedling they love, they can then dig up its tuber at the end of the year and start cloning it via tubers to sell to the public.
Key Takeaway: If you want a specific variety or color, plant tubers. If you want a fun, inexpensive way to fill a large space with a mix of surprise colors, try seeds.
Comparing Seeds and Tubers: Pros and Cons
Choosing between seeds and tubers depends on your goals for the season. Both methods are rewarding, but they require different levels of care and offer different results.
Planting Tubers
- Pros: You get the exact color, height, and flower shape you expect. The plants are generally more vigorous from the start because they have a large energy reserve in the tuber body. Most "specialty" dahlia forms, like dinnerplate dahlias or cactus types, are only available as tubers.
- Cons: Tubers are more expensive than a packet of seeds. They also require more space for storage over the winter if you live in a cold climate.
Planting Seeds
- Pros: Seeds are very affordable. You can grow dozens of plants for the price of one tuber. It is also an excellent way to attract pollinators, as seed-grown dahlias often have open centers that make it easy for bees to reach the nectar.
- Cons: You cannot predict what the flowers will look like. Seedlings are also more delicate than tubers and need to be started indoors several weeks before the last frost. Most seed-grown dahlias tend toward simpler, single-petal forms rather than the massive, complex blooms found in named tuber varieties.
How to Grow Dahlias from Tubers
If you have decided that the reliability of tubers is right for your garden, getting them started is a straightforward process. Success comes down to three main factors: timing, depth, and water.
Wait for the Warmth
The biggest mistake new gardeners make is planting tubers too early. Dahlias love warm soil and are very sensitive to frost. Wait until the soil temperature reaches about 60°F and all danger of frost has passed. If you plant them in cold, wet soil, the tubers are likely to rot before they ever have a chance to sprout.
Finding the Right Spot
Dahlias are sun-worshippers. They need at least six to eight hours of direct sunlight every day to produce those famous blooms. They also require soil that drains well. If water tends to puddle in your garden after a rain, consider planting your tubers in raised beds or containers.
Planting Step-by-Step
- Dig a hole: Make it about 4 to 6 inches deep.
- Lay the tuber flat: Place the tuber horizontally in the hole with the "eye" or the sprout pointing up toward the sky.
- Cover with soil: Fill the hole back in, but do not pack the soil down too hard.
- Hold the water: This is the most important part. Do not water your tubers until you see the first green sprouts poking through the soil. The tuber has all the moisture it needs to get started, and extra water at this stage can cause rot.
How to Grow Dahlias from Seed
Starting dahlias from seed is a great project for the early spring. Since they take a while to reach blooming size, you will want to get them started indoors about 4 to 6 weeks before your last expected frost.
Starting Indoors
Dahlia seeds are large enough to handle easily. Use a high-quality seed-starting mix and plant them about a quarter-inch deep in trays or small pots. Keep the soil consistently moist and place the trays in a warm spot. Many gardeners find that a heat mat helps speed up germination, as dahlias prefer temperatures between 65°F and 70°F to sprout.
The Seedling Stage
Once the seeds sprout, they need plenty of light. A bright south-facing window can work, but a simple shop light or grow light placed a few inches above the plants will prevent them from becoming "leggy" or weak. When the seedlings have two sets of true leaves, they are ready to be moved into slightly larger pots if it is still too cold to plant them outside.
Hardening Off
Before you move your dahlia seedlings into the garden, you must "harden them off." This means gradually introducing them to the outdoor environment. Start by putting them outside in a shaded, protected area for an hour or two, then gradually increase their time in the sun over the course of a week. This prevents the tender leaves from getting sunburned or shocked by the wind.
What to do next:
- Check your local frost dates and hardiness zone to determine your planting window.
- If planting tubers, find a sunny spot with excellent drainage.
- If starting seeds, gather your trays, soil mix, and a warm light source.
- Wait for the soil to warm up before transplanting anything outside.
From Seed to Tuber: The Lifecycle
One of the most fascinating things about dahlias is that even if you start with a tiny seed, the plant will still produce a tuber by the end of the first growing season.
This means that if you grow a dahlia from seed and happen to fall in love with its unique, one-of-a-kind bloom, you can save it! At the end of the year, you can dig up the root system and you will find a small clump of tubers. If you store these tubers and plant them the following year, you will get the exact same flower again.
This is how all the famous dahlia varieties we love today were originally discovered. Someone, somewhere, grew a dahlia from a seed, realized it was spectacular, and began saving and cloning the tubers. When you grow from seed, you are participating in that same process of discovery.
Choosing the Right Method for Your Garden
So, which should you choose? Often, the best answer is a mix of both.
For the "Cottage Garden" Look
If you want an exuberant, wild-looking garden filled with pollinators, seeds are a wonderful choice. You can plant a "bee's choice" or "landscape" mix. These plants will grow quickly and provide a massive amount of nectar for local wildlife. Because the flower forms are often simpler (single petals), the centers are exposed, making them a favorite for bumblebees.
For the "Cut Flower" Enthusiast
If your goal is to create stunning bouquets for your dining room table or to give to friends, you will likely prefer tubers. Named varieties like 'Break Out' or Labyrinth have been bred specifically for their long, strong stems, unique colors, and complex petal arrangements that look incredible in a vase.
For the Budget-Conscious Gardener
If you have a large area of new garden to fill, seeds are the most economical way to go. You can fill an entire border for the price of a single fancy tuber. Then, at the end of the year, you can dig up the tubers from your favorite seedlings and slowly transition your garden toward a more curated collection.
Simple Rules for Dahlia Success
Regardless of whether you start with a seed or a tuber, certain rules apply to all dahlias. Getting these basics right will ensure your plants stay healthy and productive from mid-summer through the first frost of autumn.
Drainage is Essential
Dahlias do not like "wet feet." In their native habitat in Mexico and Central America, they often grow on hillsides where water drains away quickly. If your soil is heavy clay, add some compost or peat moss to loosen it up. This ensures that the tubers can breathe and stay firm throughout the season.
Pinching for More Blooms
It might feel counterintuitive to snip off the top of a healthy plant, but "pinching" is the secret to a bushy dahlia with dozens of flowers. When the plant is about 12 inches tall, snip off the central growing tip just above a set of leaves. This encourages the plant to branch out, resulting in a sturdier plant and many more blooms than if you let it grow as a single tall stalk.
Water Deeply, Not Constantly
Once your dahlias are established and growing well, they need consistent moisture, especially during the heat of July and August. However, it is better to water them deeply twice a week rather than giving them a light sprinkle every day. Deep watering encourages the roots to grow further down into the soil, which makes the plant more resilient during dry spells.
Conclusion
Whether you choose the predictable beauty of tubers or the exciting variety of seeds, growing dahlias is a rewarding experience that transforms any backyard into a vibrant oasis. At Longfield Gardens, our goal is to make this process as easy and enjoyable as possible by providing high-quality tubers and the practical advice you need to see them thrive.
Gardening is all about experimentation and finding what brings you the most joy. There is no wrong way to grow a dahlia as long as you provide plenty of sun, good drainage, and a little bit of patience. By the time late summer arrives, you will be rewarded with a spectacular display of color that lasts until the very end of the season.
Final Tips for Success:
- Start with quality: Whether buying seeds or tubers, choose a trusted source to ensure healthy plants.
- Labels matter: If you are saving tubers, label them clearly in the fall so you know what you are planting in the spring.
- Enjoy the process: Not every seedling will be a masterpiece, and that is okay! Part of the fun is seeing what the garden decides to produce.
To get started on your own dahlia journey, explore the Pretty in Pink Dahlia Collection and find the perfect match for your garden's style and sun conditions.
FAQ
Can I grow dahlias in pots?
Yes, dahlias grow very well in containers. For the best results, use a pot that is at least 12 to 15 inches in diameter and ensure it has plenty of drainage holes. Smaller "gallery" or "border" varieties are usually better suited for pots than the giant dinnerplate types, which can become top-heavy and tip over in the wind. For additional guidance, see this guide to growing dahlias in pots.
How long does it take for dahlia seeds to bloom?
Dahlias grown from seed usually take about 90 to 120 days to produce their first flowers. If you start them indoors in March or April, you can expect to see blooms by July or August. The plants will then continue to bloom until the first frost kills the foliage.
Do I have to dig up my dahlia tubers every year?
This depends on your USDA hardiness zone. If you live in Zone 8 or warmer, you can often leave dahlia tubers in the ground over the winter with a thick layer of mulch for protection. If you live in Zone 7 or colder, the ground will likely freeze deep enough to kill the tubers, so you will need to dig them up and store them in a cool, frost-free place until spring. For more detailed instructions, see this dahlia tuber storage guide.
Why did my dahlia seeds produce different flowers than the parent?
Dahlias are genetically complex and do not produce seeds that are identical to the mother plant. This is because of open pollination by insects, which mixes the DNA of different dahlias in the area. To get an exact replica of a specific flower, you must plant a tuber or take a cutting from the original plant.
