Table of Contents
- Introduction
- The Short Answer: Can You Plant Two in One?
- Choosing the Right Container Size
- Selecting the Best Dahlia Varieties for Pots
- The Importance of High-Quality Soil
- How to Plant Your Two Dahlias
- Watering Habits for Container Dahlias
- Feeding Your Dahlias for Maximum Blooms
- Sunlight and Placement
- Managing Growth: Pinching and Deadheading
- Transitioning to Fall and Winter
- Creating Beautiful Combinations
- Conclusion
- FAQ
Introduction
There is a special kind of excitement that comes with planting your first dahlia tubers of the season. These remarkable plants are famous for their diversity, offering everything from tiny, star-shaped blossoms to massive flowers the size of a dinner plate. If you have limited garden space or simply want to brighten up your patio, growing dahlias in containers is a fantastic solution. Many gardeners wonder if they can double the beauty by tucking two tubers into a single container.
At Longfield Gardens, we love helping people maximize their flower power, whether they have a sprawling backyard or a sunny balcony. While dahlias are vigorous growers, they can certainly share a home if the conditions are right. Success comes down to understanding the space, nutrients, and water these "heavy feeders" require to look their best.
In this guide, we will explore the best way to plant multiple dahlias in one pot, including which varieties play well together and how to choose the right container. You will learn the simple steps to ensure both plants stay healthy and produce an abundance of blooms all summer long. You can plant two dahlias in one pot successfully by matching the container size to the mature size of the plants and providing consistent care.
The Short Answer: Can You Plant Two in One?
The quick answer is yes, you can plant two dahlias in one pot, but the size of that pot is the most important factor. Dahlias are not plants that like to be crowded. They have large, fleshy root systems called tubers, and as the plant grows, these roots expand significantly. If the pot is too small, the two plants will compete for water and nutrients, which often leads to fewer flowers and stunted growth.
As a general rule, a single dahlia plant needs about 12 inches of space in all directions to grow comfortably. This means that if you want to plant two dahlias together, you need a container that is significantly wider than a standard flower pot. For two tubers, you should look for a container that is at least 16 to 20 inches in diameter.
If you are working with a smaller pot, such as a 12-inch container, it is always better to stick to one plant. A single, healthy dahlia with plenty of room will almost always produce more flowers than two struggling plants squeezed into the same space. However, in a large planter or a half-wine barrel, you can easily fit two or even three plants for a lush, full look.
Key Takeaway While planting two dahlias in one pot is possible, the container must be large enough to hold at least 10 to 15 gallons of soil to provide enough room for both root systems to expand.
Choosing the Right Container Size
When you are planning to house two dahlias, you must think about both the width and the depth of the pot. Dahlias are top-heavy plants once they start blooming, and they need a sturdy base to prevent them from tipping over in the wind. A deep pot also allows the roots to grow downward, which helps the plant stay hydrated during the heat of the summer.
Diameter and Volume
For two dahlia tubers, a container with a 18-inch diameter is the minimum recommended size. If you can go larger, such as a 24-inch pot, your plants will be even happier. In terms of volume, look for something that holds at least 10 gallons of soil. Large resin planters, wooden barrels, or even heavy ceramic pots work well. The more soil the pot holds, the more moisture it can retain, which is vital for dahlias.
Depth Requirements
The depth of the pot is just as important as the width. Dahlia tubers are usually planted about 4 to 6 inches deep, and they need several inches of soil beneath them to grow roots. A pot that is at least 12 to 14 inches deep is ideal. This depth provides enough room for the tubers to sit comfortably while leaving space for a strong root network to develop underneath.
Drainage is Essential
No matter how large the pot is, it must have drainage holes at the bottom. Dahlias love water, but they do not like to sit in soggy soil. If the water cannot escape, the tubers can rot before they even have a chance to sprout. If you find a beautiful pot that doesn't have holes, you can usually drill them yourself using a masonry or wood bit, depending on the material.
What to do next:
- Measure your existing pots to see if they meet the 18-inch diameter requirement.
- Check for drainage holes and clear any debris blocking them.
- If buying new pots, look for "15-gallon" sizes for a two-plant arrangement.
Selecting the Best Dahlia Varieties for Pots
Not all dahlias are the same size. Some varieties stay short and bushy, while others can tower over six feet tall. When you want to plant two in one pot, choosing the right variety is the secret to a balanced, beautiful display.
Border and Dwarf Dahlias
If you are new to container gardening, border dahlias (also called dwarf or patio dahlias) are the easiest choice. Varieties like the Gallery series or Mignon dahlias stay between 12 and 18 inches tall. Because they are naturally compact, they don't require much staking, and their root systems are slightly smaller. You can easily fit two of these in a 16-inch pot without them feeling crowded.
Mid-Sized Varieties
Many decorative and cactus-type dahlias grow to about 3 feet tall. These are excellent for larger containers and offer a wide range of colors and shapes. When planting two of these together, ensure you have a heavy pot and a plan for staking, as they will become quite bushy by mid-summer.
The Challenge of Dinnerplate Dahlias
Dinnerplate dahlias are the giants of the dahlia world, producing blooms that can be 10 inches across. These plants often reach 4 or 5 feet in height and have massive root systems. While it is technically possible to plant two in a very large barrel, we usually recommend planting dinnerplate varieties individually. They are such "hungry" plants that they rarely like to share their space. If you do want two in one pot, the container must be exceptionally large, like a 30-inch wide trough.
Key Takeaway Match the plant's mature height to your pot size. Compact "border" dahlias are the best candidates for sharing a container, while tall dinnerplate varieties prefer living alone.
The Importance of High-Quality Soil
Because dahlias in pots have a limited amount of soil to draw from, the quality of that soil is critical. You cannot use ordinary garden soil in a container. Garden soil is too heavy and will pack down over time, cutting off oxygen to the roots and preventing proper drainage. For more background on dahlia care, see All About Dahlias.
The best choice is a high-quality, professional potting mix. These mixes are usually "soilless," made from a blend of peat moss or coconut coir, perlite, and vermiculite. This structure ensures the soil stays light and fluffy, which allows dahlia roots to grow quickly.
We also recommend mixing in some high-quality compost at the time of planting. A ratio of 75% potting mix and 25% compost provides a great balance of drainage and natural nutrients. Since you are asking two plants to live in one space, providing this extra "fuel" from the start will help them stay vigorous.
How to Plant Your Two Dahlias
Once you have your large pot and your potting mix, the planting process is straightforward. For a step-by-step walkthrough, see How to Plant Dahlias. Timing is the most important factor here. Dahlias are tropical plants that cannot handle frost. Wait to plant them outside until the soil is warm—ideally around 60°F—and all danger of freezing weather has passed.
Step 1: Fill the Container
Fill your pot with the potting mix and compost blend until it is about 6 inches from the top rim. Lightly press the soil down to remove large air pockets, but do not pack it tightly.
Step 2: Position the Tubers
Place your two tubers on the surface of the soil. If the dahlia tubers have a "neck" and an "eye" (the small bump where the sprout emerges), make sure the eye is pointing upward. Position the two tubers on opposite sides of the pot, roughly 8 to 10 inches apart. This gives each plant its own territory to start growing.
Step 3: Cover and Water
Cover the tubers with the remaining 4 to 6 inches of soil. Gently firm the soil over the top. At this stage, give them a very light watering just to settle the soil. Be careful not to overwater until you see green sprouts emerging from the soil. Too much water in the beginning, before the plant has leaves to process it, can lead to rot.
Step 4: Add Support Early
It is always best to place your stakes or supports in the pot at the time of planting. If you wait until the plants are large, you might accidentally drive a stake through the growing tubers. For two dahlias in one pot, a small tomato cage or two sturdy bamboo stakes work perfectly.
What to do next:
- Buy a bag of high-quality potting soil (not "topsoil" or "garden soil").
- Check your local weather forecast for the last frost date.
- Lay your tubers out in a warm spot to encourage "eyes" to sprout before planting.
Watering Habits for Container Dahlias
Watering is the most frequent task you will face when growing dahlias in pots. Because containers are exposed to air on all sides, they dry out much faster than the ground. When you have two plants in one pot, they will pull moisture out of the soil twice as fast. For more seasonal care tips, see How to Grow and Care for Dahlias in Your Garden.
Check Daily
During the height of summer, you should check your dahlia pots every day. Stick your finger about an inch into the soil. If it feels dry, it is time to water. In very hot or windy weather, you may even need to water twice a day—once in the morning and once in the late afternoon.
Water Deeply
When you water, don't just give the surface a quick splash. Water thoroughly until you see it running out of the drainage holes at the bottom. This ensures that the water is reaching the roots at the bottom of the pot and encourages the plant to grow a deep, stable root system.
Avoid Wet Foliage
Try to water at the base of the plant rather than splashing the leaves. Keeping the foliage dry helps prevent common issues like powdery mildew, which can happen if the leaves stay damp overnight.
Feeding Your Dahlias for Maximum Blooms
Dahlias are often called "hungry" plants because they require a lot of energy to produce those spectacular flowers. When two plants are sharing one pot, they will quickly use up the nutrients in the potting soil. To keep them blooming from mid-summer until the first frost, you will need to provide supplemental fertilizer.
Start a feeding routine once the plants are about 6 inches tall and have several sets of leaves. A water-soluble fertilizer is usually the easiest for container gardening. Look for a blend that is low in nitrogen and higher in phosphorus and potassium (the second and third numbers on the fertilizer label).
Too much nitrogen will give you a very tall, green plant with very few flowers. A "bloom booster" formula is often the perfect choice for dahlias. We recommend feeding your container dahlias every two weeks throughout the growing season. Always follow the instructions on the product label to ensure you are giving them the right amount.
Key Takeaway Two dahlias in one pot need consistent "food" to thrive. Use a low-nitrogen, high-phosphorus fertilizer every two weeks starting in early summer.
Sunlight and Placement
Dahlias are sun-worshippers. To produce strong stems and plenty of flowers, they need at least six to eight hours of direct sunlight every day. If they are grown in too much shade, the stems will become "leggy" and weak as they stretch toward the light, and you will see far fewer blooms.
When placing your pot, consider the "microclimate" of your space. A concrete porch or a brick patio can act as a heat sink, staying warm long after the sun goes down. While dahlias love the sun, extreme heat (above 90°F) can sometimes cause them to wilt temporarily. If you live in a very hot climate, your dahlias might appreciate a little bit of light shade during the hottest part of the afternoon.
Managing Growth: Pinching and Deadheading
To get the most out of your two-in-one dahlia pot, you should practice two simple techniques: pinching and deadheading. If you want more support on timing and technique, see How to Pinch and Stake Dahlias.
Pinching for Fullness
When your dahlia plants are about 8 to 12 inches tall and have four sets of leaves, you should "pinch" them. This means snipping off the very top of the center stem just above a set of leaves. It might feel counterintuitive to cut a healthy plant, but this tells the dahlia to stop growing upward and start growing outward. It results in a much bushier, stronger plant with many more flowering stems.
Deadheading for Continuous Blooms
Dahlias will continue to bloom as long as they don't think their job is done. Once a flower starts to fade and lose its petals, snip it off at the base of its individual stem. This process, called deadheading, prevents the plant from putting energy into making seeds. Instead, the plant redirects that energy into creating new flower buds.
What to do next:
- Mark your calendar to "pinch" the plants when they reach 10 inches tall.
- Keep a pair of clean garden snips near your pots for quick deadheading.
- Monitor for "spent" blooms every few days to keep the plant looking tidy.
Transitioning to Fall and Winter
As the weather cools in the autumn, your dahlias will eventually stop blooming. In most parts of the United States, dahlias are not hardy enough to stay outside over the winter. If you want to save them for next year, see How to Overwinter Dahlia Tubers.
Once the first frost blackens the foliage, it is time to decide what to do with your tubers.
If you want to save them for next year, you can cut the stems down to about 4 inches, carefully dig the tubers out of the pot, and store them in a cool, dry place like a basement or garage. Since they were in a pot, the tubers will likely be a tangled clump. You can leave them together or carefully separate them in the spring.
Many container gardeners treat dahlias as annuals, simply enjoying them for the season and starting fresh with new varieties from us the following spring. Either way, the joy they bring during the summer months makes them well worth the effort.
Creating Beautiful Combinations
Planting two dahlias in one pot gives you the chance to play with color and texture. You can choose two of the same variety for a uniform, high-impact look, or you can mix and match.
Monochromatic Elegance
Try planting two different varieties in the same color family, such as pink dahlias. This creates depth and interest while keeping the look sophisticated.
High Contrast
For a bold statement, pair a bright yellow dahlia with a dark purple variety. The contrast will make both colors pop and create a focal point on your patio.
Staggered Heights
If your pot is very large, you can plant a slightly taller variety in the center and a shorter, "mignon" type near the edge. This creates a tiered effect that looks professionally designed.
Conclusion
Planting two dahlias in one pot is a wonderful way to enjoy more flowers in a small space. As long as you provide a large enough container, high-quality soil, and plenty of sunshine, your dahlias will reward you with a spectacular show of color. Remember that container plants rely entirely on you for their water and nutrients, so consistent care is the key to success.
We believe that gardening should be a rewarding and relaxing experience. By getting the basics of pot size and drainage right from the start, you set yourself up for a season of beautiful blooms. Whether you are a seasoned grower or just starting out, dahlias in containers are a simple win for any sunny spot.
Key Takeaway Success with two dahlias in one pot depends on space and "food." Use a 16-20 inch pot, high-quality potting mix, and regular fertilizer to keep both plants healthy and blooming.
Ready to start your container garden? Explore the wide variety of dahlia tubers at Longfield Gardens and find the perfect pair for your patio this season.
FAQ
What is the smallest pot size for two dahlias?
For two dahlia tubers, you should use a pot that is at least 16 to 18 inches in diameter and about 12 inches deep. Smaller pots do not hold enough soil or moisture to support two mature dahlia plants, which can lead to poor blooming and weak stems.
Do I need to stake dahlias if they are in a pot?
Yes, most dahlias grown in pots will eventually need some support, especially the taller varieties. A heavy rain or a strong wind can easily topple a top-heavy dahlia. Placing a stake or a small tomato cage in the pot at the time of planting is the best way to keep them upright.
Can I mix different dahlia varieties in the same pot?
You can certainly mix varieties, but it is best to choose two that have similar growth habits. For example, planting two different "border" dahlias together works well because they will grow at the same rate and won't shade each other out. Avoid planting a tiny dwarf variety with a giant dinnerplate variety, as the larger plant will likely overwhelm the smaller one.
How often should I water my dahlias in a shared pot?
Because two plants use more water than one, you should check the soil daily. In the heat of summer, container dahlias often need water every single day. If the top inch of soil feels dry to the touch, give the pot a thorough soak until water runs out the bottom.