Introduction
There is nothing quite like the excitement of seeing your first dinnerplate dahlia begin to unfurl in the garden. These spectacular flowers are a favorite for home gardeners across the country because they offer incredible color and variety from midsummer all the way until the first frost. Whether you are dreaming of massive, pillowy blooms or tiny, perfectly symmetrical pompons, dahlias are a rewarding choice for any skill level.
At Longfield Gardens, we want to help you feel confident as you plan your summer garden. One of the most common questions we hear is whether these plants grow from bulbs or something else entirely. While the term "dahlia bulbs" is used by many people, there is actually a fascinating bit of plant biology behind how these flowers grow.
This guide is designed for home gardeners who want to understand exactly what they are planting and how to get the best results. We will cover the difference between bulbs and tubers, what to look for when you receive your plants, and the simple steps you can take to ensure a season full of beautiful blooms. Understanding these basics is the first step toward a more beautiful yard.
Do Dahlias Grow from Bulbs or Tubers?
If you have ever called them "dahlia bulbs," do not worry—you are in good company. In the gardening world, "bulb" is often used as a catch-all term for any plant that grows from a fleshy, underground storage organ. However, if you want to be technically correct, dahlias actually grow from tubers.
While they look similar to the bulbs you might plant in the fall, like tulips, or daffodils, dahlias have a different way of storing energy. True bulbs, such as onions or lilies, are made of fleshy layers called scales. If you cut a tulip bulb in half, you can see these layers tucked inside each other. Tubers, on the other hand, are solid, starchy structures.
Dahlia tubers function much like a potato. They are the plant’s pantry, holding all the water and nutrients necessary to kick-start growth in the spring. During the growing season, the plant uses this stored energy to send up stems and leaves. As the summer progresses, the plant actually creates new tubers underground to store energy for the following year.
Why the Name "Bulb" Sticks
Even though they are technically tubers, many retail stores and online shops list them as bulbs. This is mostly for simplicity. Most gardeners are familiar with the idea of planting a "bulb" to get a flower. Whether you call them bulbs or tubers, the care remains the same.
The most important thing to remember is that because they are tubers, they have specific needs regarding moisture and temperature. They are more sensitive to cold and excess water than many of the hardy bulbs we plant in the autumn.
Key Takeaway: Dahlias grow from tubers, which are solid, starchy roots similar to potatoes. While often called "bulbs" for convenience, they require specific handling to protect their unique anatomy.
Understanding the Anatomy of a Dahlia Tuber
When you receive a dahlia from us, it may arrive as a single tuber or a small clump of tubers. At first glance, they might look like a bunch of brown carrots or sausages. However, each part of that tuber plays a vital role in the plant's success.
There are three main parts to look for on a dahlia tuber: the body, the neck, and the crown. The body is the largest, fleshy part where the nutrients are stored. The neck is the narrow portion that connects the body to the crown. The crown is the part that was once attached to the main stem of the previous year's plant.
A dahlia tuber must have all three of these parts to be viable. If the neck is broken or the body is detached from the crown, the tuber will not grow. This is because the growth points are not located on the body itself.
The Importance of the "Eye"
The most critical part of the dahlia tuber is the "eye." Much like the eyes on a potato, these are the small buds from which new sprouts emerge. On a dahlia, the eyes are always located on the crown, right where the neck meets the stem tissue.
Eyes can be very difficult to see early in the season. They often look like tiny, pale bumps or pimples. As the weather warms up, these eyes will begin to swell and may turn pink or green as they prepare to sprout.
If you are having trouble spotting the eyes on your tubers, do not panic. You can place the tuber in a warm, bright spot for a few days to encourage the eyes to "wake up." Some gardeners like to put them in a tray with a little bit of damp potting soil to help the sprouts appear.
What to Do When You Receive Your Tubers
- Check the connections: Make sure the tubers are firmly attached to the crown.
- Look for the eyes: Identify at least one growth point near the neck.
- Inspect for firmness: The tubers should feel firm, like a fresh carrot, not mushy or hollow.
- Store safely: If it is too early to plant, keep them in a cool, dark, and dry place until the soil warms up.
Does Tuber Size Matter for Flower Quality?
One of the biggest misconceptions in dahlia gardening is that a larger tuber will produce a larger plant or bigger flowers. In reality, size is rarely an indicator of performance. Different dahlia varieties naturally produce different sizes of tubers.
Some varieties, like the famous 'Cafe au Lait,' often produce large, chunky tubers. Other varieties might produce tubers that are no thicker than your pinky finger. Both are equally capable of growing into a five-foot-tall plant covered in blooms.
As long as the tuber has a healthy eye and enough stored energy to get the first few leaves above the soil, it will be successful. Once the plant has established its root system and several sets of leaves, it stops relying on the mother tuber and begins to pull nutrients directly from the soil.
Clumps vs. Individual Tubers
Depending on where you source your plants, you may receive a single tuber or a whole clump. In the United States, most specialty growers sell individual tubers. In Europe and Holland, it is more common to see clumps.
There is no major advantage to one over the other. A clump might offer "insurance" by having multiple eyes, but a single, healthy tuber is more than enough to grow a vigorous plant. We ensure that our tubers are high quality and ready to perform, regardless of their specific shape or size.
Choosing the Best Planting Spot
Success with dahlias starts with the right location. Because they are native to the high plains of Mexico, they love sunshine and well-drained soil. If you get these two factors right, most of your work is already done.
Sunlight Requirements
Dahlias are sun-worshipers. To produce those famous, heavy blooms, they need at least six to eight hours of direct sunlight every day. If they are planted in too much shade, the plants will become "leggy," meaning they grow tall and thin as they reach for the light. Shaded dahlias also produce fewer flowers and may have weaker stems.
Soil and Drainage
"Drainage" simply refers to how fast water leaves the soil. Dahlias have a love-hate relationship with water. They need it to grow, but they cannot stand to have their tubers sitting in soggy, wet earth. If the soil stays too wet for too long, the tubers can rot before they even have a chance to sprout.
The ideal soil for dahlias is loose, crumbly, and rich in organic matter. If you have heavy clay soil that stays wet, you might consider planting in raised beds or containers. Adding a bit of compost to your planting area is an easy win that improves soil structure and provides gentle nutrients.
Key Takeaway: Pick a spot with at least six hours of full sun and soil that does not stay soggy after a rain. Good drainage is the best way to prevent tuber rot.
Simple Steps for Planting Dahlia Tubers
Once the threat of frost has passed and your soil has warmed up, it is time to get your dahlias in the ground. Timing is much more important than any gardening "trick" you might find online.
Determining the Right Time to Plant
Dahlias are tropical plants at heart. They are very sensitive to cold soil and freezing temperatures. A good rule of thumb is to plant your dahlias around the same time you would plant tomatoes or peppers in your garden.
In most regions, this is late spring. Ideally, the soil temperature should be around 60°F. If you plant too early in cold, wet soil, the tuber will just sit there and may eventually rot. Waiting for the right warmth ensures the plant takes off quickly.
Depth and Spacing for Success
Getting the depth and spacing right gives your plants the room they need to breathe and grow. For a detailed guide, see how deeply dahlia tubers should be planted.
- Dig a hole: Your hole should be about 4 to 6 inches deep.
- Place the tuber: Lay the tuber horizontally in the hole with the eye (or the sprout) facing up. If it is a clump, just set it in the hole with the old stem pointing toward the sky.
- Space them out: Small border dahlias can be spaced 12 to 18 inches apart. Larger varieties, like Dinnerplates, need at least 2 feet of space between plants to allow for air circulation.
- Cover with soil: Fill the hole back in with loose soil, but do not pack it down too hard.
What to Do Next
- Label your plants: It is easy to forget which variety is which once they are under the dirt. Use a waterproof marker and a garden stake.
- Skip the water (initially): If your soil is slightly damp, you do not need to water your dahlias until you see the first green sprouts poking through the ground. This protects the tuber from rotting while it is dormant.
- Watch for sprouts: You should see green growth appearing within 2 to 4 weeks, depending on the weather.
Caring for Your Dahlias Through the Season
Once your dahlias are up and growing, they are relatively low-maintenance. A few simple habits will keep them healthy and blooming until autumn.
Water Correctly, Not Constantly
As we mentioned earlier, the rule for most perennials and tubers is "deeply, then let it dry a bit." Once the plants are established and about a foot tall, they will need more regular water, especially during the heat of the summer.
Instead of a light daily sprinkle, give them a long, deep soak two or three times a week. This encourages the roots to grow deep into the ground, making the plant more stable and drought-resistant. Always try to water at the base of the plant rather than over the leaves to keep the foliage dry and healthy.
The Magic of Pinching
If you want a dahlia plant that is bushy and covered in flowers, you should "pinch" it. This might sound scary, but it is actually one of the best things you can do for the plant.
When the plant is about 12 to 16 inches tall and has four sets of leaves, take a pair of clean garden snips and cut off the very top of the center stem. This tells the plant to stop growing straight up and start growing side branches. More branches mean more stems, and more stems mean more flowers. It is an easy win for any gardener.
Staking for Support
Many dahlia varieties grow quite tall and produce very large, heavy flowers. A summer rainstorm or a gust of wind can easily topple a top-heavy plant. To prevent this, it is a good idea to provide some support.
You can use wooden stakes, bamboo poles, or even tomato cages. It is best to put your stakes in the ground at the time of planting so you do not accidentally poke a hole through the tuber later. As the plant grows, gently tie the main stem to the stake using soft garden twine or strips of fabric.
Key Takeaway: To get the most flowers, pinch the center stem when the plant is about a foot tall. Support tall varieties with stakes early in the season to prevent storm damage.
Dealing with Dormancy and Storage
Dahlias are not winter-hardy in most of the United States (typically zones 8 and colder). This means that if you leave them in the ground over a freezing winter, the tubers will turn to mush and will not grow back the following year. For help matching your garden to local conditions, use the Hardiness Zone Map.
Because they grow from tubers, however, you have a unique opportunity to save them. This is one of the reasons gardening with dahlias is so rewarding—you can treat your initial purchase as an investment.
Lifting and Storing for Next Year
If you live in a cold climate and want to keep your dahlias, you can lift and store your dahlia tubers in the fall. After the first frost turns the foliage black, cut the stems down to about 4 inches. Carefully dig up the clump of tubers, making sure not to nick or break them.
Gently brush off the excess soil and let the tubers dry in a protected area for a few days. Once they are dry, you can store them in a box filled with slightly damp peat moss, vermiculite, or wood shavings. Keep the box in a cool, dark place that stays between 40°F and 50°F, like a basement or a crawlspace.
One Change at a Time
If your dahlias didn't perform exactly as you hoped, do not feel discouraged. Gardening is a learning process influenced by weather and soil. When troubleshooting, try changing just one thing next year—perhaps move them to a sunnier spot or adjust your watering schedule. Observing how the plant reacts to one change is the best way to become a dahlia expert.
Conclusion
Dahlias are some of the most spectacular flowers you can grow in your home garden. While they technically grow from tubers rather than bulbs, the joy they bring is the same regardless of the botanical name. By focusing on the basics—sunlight, good drainage, and correct planting depth—you can enjoy a summer filled with vibrant, breathtaking blooms.
At Longfield Gardens, we take pride in providing high-quality tubers that are ready to thrive in your yard. We want your gardening experience to be successful and enjoyable from the moment your package arrives until the final frost of the year.
- Plan ahead: Choose a sunny spot with well-drained soil.
- Wait for warmth: Plant your tubers only after the soil is warm and frost is gone.
- Give them a boost: Pinch the stems early for more flowers and use stakes for support.
- Enjoy the harvest: Cut flowers often to encourage the plant to keep blooming.
"The secret to beautiful dahlias isn't found in complicated tricks, but in the simple satisfaction of watching a small tuber transform into a garden masterpiece."
Ready to start your dahlia journey? We invite you to explore our dahlia collections and find the perfect varieties to bring color and beauty to your landscape this season.
FAQ
Are dahlia tubers and bulbs the same thing?
While people often use the terms interchangeably, they are botanically different. Dahlias grow from tubers, which are solid, starchy roots similar to a potato, whereas true bulbs like onions have layers. However, in most gardening contexts, calling them "dahlia bulbs" is perfectly fine and understood by most growers.
Can I plant a dahlia tuber that is shriveled?
Yes, as long as the tuber still feels somewhat firm and is not completely dried out or "hollow" feeling. Many tubers look a bit shriveled after winter storage, but once they are in the ground, they will absorb moisture and begin to grow. The most important factor is ensuring there is a healthy "eye" on the crown.
Do I need to water dahlias right after planting?
Unless your soil is bone-dry, it is usually better to wait until you see the first green sprouts before you start watering. Because the tuber is currently dormant, it doesn't have roots to take up water yet. Too much moisture in the early stages can lead to rot, so let the natural soil moisture do the work until the plant wakes up.
How many flowers will one dahlia tuber produce?
One single healthy tuber can grow into a large, bushy plant that produces dozens of flowers over the course of a single season. The more you cut the flowers for bouquets, the more the plant will be encouraged to produce new buds. Most varieties will continue to bloom from mid-July until the first hard frost.
