Table of Contents
- Introduction
- Getting Started with Dahlia Tubers
- Choosing the Best Location
- When to Plant Dahlias
- How to Plant Dahlia Tubers: Step-by-Step
- Watering and Initial Care
- Supporting Your Dahlias
- Pinching for More Blooms
- Planting Dahlias in Containers
- Simple Troubleshooting Tips
- Enjoying Your Harvest
- Conclusion
- FAQ
Introduction
There is nothing quite like the excitement of seeing the first dinnerplate dahlia unfurl its petals in midsummer. These spectacular flowers are the crown jewels of the summer garden, offering a variety of colors and shapes that few other plants can match. Whether you are looking for petite pompon varieties or massive blooms the size of a dinner plate, dahlias provide a rewarding gardening experience that lasts until the first frost.
At Longfield Gardens, our Dahlia Collections make it easy to fill your yard with these incredible blossoms. Planting dahlias is an achievable project for gardeners of all skill levels, and getting the basics right from the start ensures a season full of color. This guide will walk you through the essential steps of site selection, soil preparation, and planting techniques to get your garden off to a great start.
By following a few simple steps, you can enjoy a continuous harvest of beautiful flowers for your home and garden. Success begins with understanding dahlias and what these tuberous plants need to thrive.
Getting Started with Dahlia Tubers
Before you dig your first hole, it is helpful to understand dahlia tubers. Dahlias grow from tubers, which are thickened underground parts that store energy for the plant. While they may look like a bunch of sweet potatoes or carrots, these humble-looking roots hold the potential for spectacular growth.
When your order arrives, open the box immediately to check your tubers. We take great care to ensure that every tuber we ship is healthy, firm, and ready to grow, and our 100% quality guarantee means we stand behind the health and variety of our plants, so you can start your gardening season with confidence. If you aren't ready to plant right away because the weather is still too cold, store them in a cool, dark, and dry place—like a basement or a garage that stays above freezing—until the time is right.
Inspecting for "Eyes"
A viable dahlia tuber must have an "eye." An eye is a growth bud, much like the eyes you see on a potato in your pantry. These are located on the "crown" of the tuber, which is the area where the tuber meets the old stem. Sometimes these eyes are very easy to see as small green or pink bumps, and other times they are dormant and harder to spot.
Do not worry if you cannot see an eye right away. As the tuber warms up, the eye will naturally begin to swell and sprout. If the tuber feels firm and the neck (the thin part connecting the tuber to the crown) is intact, it is ready for the garden.
Key Takeaway: A healthy dahlia plant grows from a firm tuber with at least one viable eye. Tuber size does not determine the size of the flower; even a small tuber can produce a massive, healthy plant.
Choosing the Best Location
Matching the plant to the right spot in your yard is the most important rule for gardening success. Dahlias have a few specific requirements that, when met, make the rest of the season much easier.
Sun Exposure
Dahlias are sun-loving plants. For the best results and the most flowers, choose a spot that receives at least six to eight hours of direct sunlight every day. Morning sun is particularly beneficial as it helps dry dew off the leaves, which keeps the plants healthy. If you live in an exceptionally hot climate where afternoon temperatures regularly soar, your dahlias might appreciate a little bit of dappled shade during the hottest part of the day to prevent the petals from fading.
Protection from Wind
Because many dahlia varieties grow quite tall—some reaching four or five feet—and produce heavy flowers, they can be sensitive to strong winds. Try to find a location that offers some protection, such as near a fence or on the lee side of a building. However, ensure there is still plenty of airflow around the plants to keep the foliage dry and healthy.
Soil and Drainage
The term "drainage" simply refers to how fast water leaves the soil after it rains. Dahlias need soil that drains well. If water sits in a puddle for hours after a storm, the tubers may get too wet and rot.
We recommend planting in loose, fertile soil. If you have heavy clay soil (which feels sticky and holds water) or very sandy soil (which drains too fast and doesn't hold nutrients), you can improve it by adding organic matter. Compost, aged manure, or shredded leaves are excellent choices for amending your garden beds. This helps create a crumbly soil texture that dahlia roots love.
When to Plant Dahlias
Timing is more important than any gardening "trick." Because dahlias are native to the warm climates of Mexico and Central America, they have no tolerance for frost. Planting too early in cold, wet soil is a common mistake that can lead to disappointment.
Soil Temperature Matters
The best time to plant your dahlias is when the soil has warmed up to about 60°F. A good rule of thumb for many gardeners in the United States is to plant dahlias around the same time you would plant tomatoes or peppers. In most regions, this is late spring, usually May or early June. If you're not sure when conditions are right in your area, check the Hardiness Zone Map.
If you aren't sure about your soil temperature, you can use a simple soil thermometer or wait until all danger of spring frost has passed and the nights are consistently warm. Waiting for the right conditions ensures the tubers wake up quickly and start growing vigorously.
The Head Start Option
If you live in a region with a short growing season and want flowers as early as possible, you can start your tubers indoors about four to six weeks before the last frost date. Plant them in pots with potting soil and place them in a warm, sunny window or under grow lights. By the time the weather is warm enough to move them outside, you will have established plants ready to take off.
What to Do Next:
- Check your local frost dates to determine your planting window.
- Monitor your soil temperature with a thermometer.
- Prepare your garden beds by clearing weeds and adding a layer of compost.
How to Plant Dahlia Tubers: Step-by-Step
Once your soil is warm and your site is ready, it is time to get your dahlias in the ground. Following the correct depth and spacing guidelines is a quiet winner for a successful garden.
1. Dig the Hole
Start by digging a hole that is about 6 to 8 inches deep. If you are planting in a row, you can dig a long trench instead of individual holes. This is a good time to mix in a small handful of bone meal or a balanced, slow-release fertilizer into the bottom of the hole to give the plant a gentle boost as it develops. For more detail, see How Deep Should I Plant Dahlia Tubers?.
2. Place the Tuber
Lay the dahlia tuber horizontally in the hole. It is a common misconception that they should be planted vertically like a carrot. Instead, lay them flat on their side. Ensure the "eye" or the sprout is pointing toward the sky. If you have a clump of tubers, lay the entire clump flat with the old stem pointing upward.
3. Spacing the Plants
Dahlias need room to breathe and grow. Proper spacing depends on the variety:
- Large Varieties (Dinnerplate and cactus dahlias): Space these 18 to 24 inches apart.
- Medium Varieties (PomPon dahlias): Space these 12 to 18 inches apart.
- Small/Bedding Varieties: Space these 9 to 12 inches apart.
Giving them enough space ensures that each plant gets plenty of sunlight and that air can move freely between the leaves, which helps prevent common garden issues.
4. Backfill the Soil
Cover the tuber with about 3 to 4 inches of soil. Do not fill the hole all the way to the top yet if you want to be extra careful. Some gardeners prefer to leave a slight depression and fill it in gradually as the sprout grows taller. However, covering it with a few inches of soil right away is perfectly fine and works well for most home gardens.
5. Add Support Early
It is much easier to install stakes at planting time than it is to try to do it later when the plant is large. By putting your support in now, you avoid accidentally driving a stake through the tuber later in the season. Place a sturdy wooden or metal stake (about 5 to 6 feet tall) a few inches away from where you buried the tuber.
Key Takeaway: Plant dahlia tubers horizontally, about 4 to 6 inches deep, with the eyes facing up. Spacing them correctly and providing support early sets the stage for a tidy, upright garden.
Watering and Initial Care
Watering correctly is vital during the first few weeks after planting. It is important to remember that until the dahlia tuber sends up a green sprout and develops leaves, it does not have a way to "drink" much water. For more growing basics, see How to Best Grow Dahlias.
The "No Water" Rule
In many parts of the country, there is enough natural moisture in the soil in late spring to sustain the tuber until it sprouts. We recommend avoiding heavy watering right after planting. If the soil is kept too wet before the plant starts growing, the tuber may rot.
Wait until you see the first green shoots peeking through the soil. Once the plant is a few inches tall and has developed its first sets of leaves, you can begin a regular watering schedule.
Watering Established Plants
As the weather warms up and the plants grow larger, they will need more water. The goal is to water deeply once or 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.
If you are gardening in a very sandy soil or in a hot, dry climate, you may need to water more frequently. Using a soaker hose or drip irrigation is a great way to deliver water directly to the base of the plant while keeping the foliage dry.
Supporting Your Dahlias
Because dahlias produce such large, heavy blooms, they almost always need a little help staying upright. How to Pinch and Stake Dahlias is a helpful guide for keeping tall plants supported.
Individual Staking
The most common method for home gardeners is to tie each plant to an individual stake. As the plant grows, use soft garden twine or strips of fabric to gently secure the main stem to the stake every 12 to 18 inches. Avoid tying the twine too tightly; you want to give the stem room to thicken as the plant matures.
Tomato Cages
For shorter or medium-sized dahlia varieties, a heavy-duty tomato cage can be an easy and effective support system. Place the cage over the planting spot shortly after burying the tuber. The plant will grow up through the rings, and the cage will provide support from all sides without the need for tying.
The Corral Method
If you are planting a long row of dahlias, you might find the "corral" method more efficient. Drive sturdy stakes or T-posts into the ground at the four corners of your dahlia bed and at intervals along the sides. Wrap garden twine around the perimeter of the posts at heights of 12 inches and 24 inches. The plants will grow up inside this "box" of twine, which keeps them from flopping over into the pathways.
Pinching for More Blooms
If you want your dahlia plants to be bushier and produce more flowers, you should "pinch" them. Pinching is a simple technique where you remove the top of the main stem to encourage the plant to grow more side branches.
When your dahlia plant is about 12 to 16 inches tall and has four sets of leaves, use your fingers or a clean pair of garden snips to remove the very top of the center stalk. It might feel a bit strange to cut off the top of a healthy growing plant, but don't worry! This simple step signals the plant to put its energy into the side buds.
The result is a sturdier, more compact plant with more stems. And because each stem produces flowers, pinching directly leads to a more colorful garden and more blooms for your vases.
What to Do Next:
- Once your plant reaches 12 inches, identify the center growing tip.
- Snip off the top 2-3 inches of the center stem.
- Watch for new growth appearing from the leaf nodes below the cut.
Planting Dahlias in Containers
If you have limited space or want to decorate your patio with vibrant color, you can successfully plant dahlias in containers. Many dwarf and border varieties are perfectly suited for pot culture, though even large varieties can grow in containers if the pot is big enough.
Choosing the Right Pot
For a single dahlia plant, choose a container that holds at least 2 to 5 gallons of soil. Ensure the pot has plenty of drainage holes in the bottom. A heavy pot, such as one made of ceramic or terra cotta, is a good choice because it provides a sturdy base that won't tip over when the plant gets tall and top-heavy. If you want a broader guide to potted dahlias, see Can Dahlias Grow in Containers?.
Potting Mix and Planting
Use a high-quality, well-draining potting mix. Avoid using garden soil in pots, as it is too heavy and can become compacted, which prevents air from reaching the roots.
Plant the tuber about 4 to 6 inches deep, just as you would in the ground. Because containers dry out faster than the garden, you will need to monitor the moisture levels more closely. Check the soil daily during the heat of summer; if the top inch of soil feels dry, it is time to water.
Fertilizing Pots
Plants in containers need a bit more "food" because nutrients wash out of the soil every time you water. Start with a slow-release fertilizer mixed into the potting soil, and then use a water-soluble fertilizer every two weeks once the plant begins to bloom.
Simple Troubleshooting Tips
Gardening is a journey, and sometimes things don't go exactly as planned. Most dahlia issues have simple solutions that focus on getting the basics back on track.
Slugs and Snails
Young dahlia sprouts are a favorite snack for slugs and snails. To protect your plants during the vulnerable early stages, you can use organic slug bait or check your plants in the early morning to remove any visitors by hand. Once the plants get larger and the stems become tougher, they are much less attractive to these pests.
Slow Growth
If your dahlias seem to be sitting still, the most likely culprit is temperature. Dahlias really wait for the heat. If you had a cool, rainy spring, the plants might stay small until the summer sun truly arrives. Once the nights stay warm, you will likely see a sudden burst of growth.
Yellow Leaves
If the bottom leaves of your dahlia plants are turning yellow, it could be a sign of overwatering or a lack of nutrients. Check the soil moisture; if it feels soggy, let it dry out a bit before watering again. If the soil is fine, try a light application of a balanced liquid fertilizer to give the plant the nitrogen it needs to stay green.
Enjoying Your Harvest
One of the best things about dahlias is that the more you cut the flowers, the more the plant will produce. This makes them the ultimate choice for a cutting garden.
When to Cut
Unlike some flowers that continue to open after they are cut, dahlias should be harvested when they are nearly fully open. Check the back of the flower head; the petals should be firm and not starting to wilt or turn brown.
Cut the stems in the morning when the plants are most hydrated. Use sharp, clean snips and place the stems immediately into a bucket of room-temperature water. To encourage the plant to grow longer stems for your next bouquet, make your cut just above a set of leaves lower down on the plant.
Deadheading
If you decide to leave the flowers on the plant to enjoy in the garden, you still need to "deadhead." Deadheading simply means removing the flowers as they begin to fade. This prevents the plant from putting energy into producing seeds and encourages it to keep pumping out new flower buds all season long.
Key Takeaway: Regular cutting and deadheading are the keys to a long bloom season. Harvest flowers when they are almost fully open for the best vase life.
Conclusion
Planting dahlias is a rewarding way to add spectacular color and variety to your summer landscape. By choosing a sunny spot, waiting for the soil to warm, and providing a little bit of support, you can grow these stunning flowers with ease. We at Longfield Gardens are proud to provide the high-quality tubers you need to make your gardening dreams a reality.
Remember that gardening is a learning process, and every season brings new experiences. Dahlias are resilient, generous plants that will reward your efforts with armloads of blooms from July until the first autumn chill.
"Dahlias are the workhorses of the late-summer garden, providing a level of color and drama that few other plants can match. With just a few simple steps at planting time, you can set yourself up for months of floral beauty."
We encourage you to pick a few of your favorite colors and start your dahlia journey this spring. For more information on plant care and garden planning, visit our Garden Basics How To.
FAQ
When is the best time to plant dahlia tubers?
The best time to plant is in late spring, after all danger of frost has passed and the soil has warmed to at least 60°F. This usually aligns with the time you would plant other warm-weather crops like tomatoes. Planting in cold, wet soil can lead to the tubers rotting before they have a chance to sprout.
How deep and how far apart should I plant dahlias?
Dahlia tubers should be planted about 4 to 6 inches deep. Lay the tuber horizontally with the eye or sprout facing upward. Spacing depends on the variety: large dinnerplate types need 18 to 24 inches of space, while smaller border varieties can be planted 12 to 15 inches apart.
Do I need to water my dahlias immediately after planting?
Unless your soil is extremely dry, it is best to wait until you see the first green sprouts emerge before you begin regular watering. Dahlia tubers are prone to rot if they sit in cold, soggy soil without active growth. Once the plant is established with several sets of leaves, you can begin watering deeply once or twice a week.
Why is it important to "pinch" dahlia plants?
Pinching involves snipping off the top of the main center stem when the plant is about 12 to 16 inches tall. This encourages the plant to grow more side branches rather than just one tall stalk. A pinched plant is bushier, sturdier, and ultimately produces many more flowers throughout the season.