Table of Contents
- Introduction
- Why the Ground is a Great Home for Dahlias
- Finding the Right Spot in Your Garden
- Preparing Your Soil for Success
- Timing is Everything
- Understanding the Dahlia Tuber
- How to Plant Dahlias in the Ground: Step-by-Step
- The Most Important Rule: Don't Water Yet
- Growing and Caring for Your Dahlias
- Managing Pests and Challenges
- Staking and Support
- Can Dahlias Stay in the Ground Over Winter?
- Enjoying the Harvest
- Designing Your In-Ground Dahlia Garden
- A Note on Shipping and Planning
- Realistic Expectations
- Conclusion
- FAQ
Introduction
Dahlias are the undisputed stars of the late summer garden, offering a variety of colors and shapes that few other flowers can match. There is a special kind of excitement that comes with seeing those first green shoots emerge from the soil. It marks the beginning of a season filled with armloads of fresh bouquets and vibrant backyard views. If you have been dreaming of a garden filled with these spectacular blooms, you might be wondering if you can plant them directly into your backyard soil.
The short answer is a resounding yes. In fact, growing dahlias in the ground is the traditional and most common way to enjoy these plants. At Longfield Gardens, we believe that everyone can find success with these stunning flowers by following a few straightforward steps. Whether you have a sprawling suburban lot or a small sunny patch by the fence, the ground provides the space and nutrients your dahlias need to thrive.
This guide will explain exactly how to prepare your site, when to get your tubers in the dirt, and how to care for them throughout the season. For a visual walkthrough, see our How to Plant Dahlias. We will cover everything from soil health to winter storage so you can feel confident in your gardening journey. By the end of this article, you will see that planting dahlias in the ground is an achievable and rewarding project for any home gardener.
Why the Ground is a Great Home for Dahlias
Dahlias grow from thickened underground stems called tubers. These tubers look a bit like a bunch of sweet potatoes or carrots. While dahlias are often grown in containers or raised beds, planting them directly in the ground offers several distinct advantages.
First, the ground provides a stable environment for the root system. Soil in the ground stays cooler and holds moisture more consistently than the soil in a pot. This stability helps the plant stay resilient during the hottest weeks of July and August. In-ground planting also gives the tubers plenty of room to expand. As your dahlia grows during the summer, it creates new tubers underground. Having more space allows for a larger, healthier tuber clump by the end of the season.
Additionally, planting in the ground is often the simplest way to start. You do not need to buy specialized pots or expensive potting mixes. Most backyard soil can be easily adapted to meet a dahlia’s needs with just a bit of organic matter. If you have a sunny spot with soil that drains well, you already have the most important ingredients for success.
Finding the Right Spot in Your Garden
Before you pick up a shovel, you need to evaluate your garden to find the perfect location. Dahlias have two main requirements: sun and drainage. If you get these two things right, the rest of the process is much easier.
Follow the Sun
Dahlias are sun worshippers. 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 stems will grow tall and "leggy" as they stretch for light. These weak stems often flop over and produce fewer flowers. Look for a spot that is not shaded by large trees or the shadow of your house during the peak hours of the day.
Check Your Drainage
Drainage refers to how quickly water moves through the soil. Dahlias love water once they are growing, but their tubers are very sensitive to sitting in soggy conditions. If water stays in a puddle on your lawn for hours after a rainstorm, that spot is not ideal for dahlias.
To test your drainage, dig a small hole about 12 inches deep and fill it with water. If the water drains away within an hour, your drainage is excellent. If it takes several hours or a full day, you may need to improve the soil or find a higher spot in the yard. Planting in a location with poor drainage is a common reason tubers fail to sprout, so taking the time to check this now is a great "easy win."
Key Takeaway: Success starts with the "Right Plant, Right Place" rule. Ensure your dahlias have a sunny location and soil that allows water to move away from the tubers quickly.
Preparing Your Soil for Success
You do not need perfect soil to grow beautiful dahlias, but a little preparation goes a long way. Most garden soil is either heavy in clay or very sandy. Both can work well if you add some organic matter.
Amending Clay or Sandy Soil
If your soil is heavy clay, it can feel sticky and hold onto too much water. Adding compost or well-rotted manure helps break up the clay particles and improves drainage. If your soil is sandy, it might drain too fast, leaving the plants thirsty. In this case, compost helps the soil hold onto just enough moisture and nutrients to keep the plants happy.
We recommend mixing a few inches of compost into the top six to eight inches of your soil before planting. This creates a loose, crumbly texture that makes it easy for young roots to grow. It also provides a slow-release source of food for the plants as they develop.
A Note on Soil Health
Dahlias prefer a slightly acidic soil, but they are generally flexible. If you are unsure about your soil quality, your local university extension service can provide a soil test. However, for most home gardeners, simply adding compost is the only "trick" you need. Avoid using heavy fertilizers right at planting time, as this can sometimes be too much for the young tuber to handle.
Timing is Everything
When it comes to planting dahlias in the ground, timing is more important than almost anything else. Because dahlias are tropical plants originally from Mexico, they have no tolerance for frost. More importantly, the tubers are sensitive to cold, damp soil.
The Danger of Planting Too Early
It can be tempting to plant your tubers as soon as the first warm day of spring arrives. However, if the ground is still cold and wet from spring rains, the tuber may rot before it ever has a chance to sprout. We suggest waiting until all danger of frost has passed in your area.
The Soil Temperature Rule
A great rule of thumb is to wait until your soil temperature reaches about 60°F. This is usually around the same time you would plant tomatoes or peppers in your garden. If you do not have a soil thermometer, wait until the ground feels warm to the touch and the spring weeds have started to grow vigorously. In most parts of the United States, this happens between late April and early June.
Understanding the Dahlia Tuber
When you receive your tubers from us at Longfield Gardens, they might look a bit like a quiet, brown root. However, inside that tuber is all the energy the plant needs to get started.
Every viable dahlia tuber must have an "eye." The eye is a small growth point located on the "crown" of the tuber, where the tuber meets the old stem. It looks like a tiny bump or a small green sprout. If a tuber does not have an eye, it will not grow. We ensure our tubers are high quality and true to variety, but it is always fun to look for that little eye when you are getting ready to plant. Do not worry if the eye is hard to see; once the tuber is in warm soil, that eye will wake up and start growing.
How to Plant Dahlias in the Ground: Step-by-Step
Once the weather is warm and your soil is prepped, it is time to plant. This process is simple and takes very little time.
1. Dig the Hole
Dig a hole that is about 4 to 6 inches deep. If you are planting several dahlias, space the holes 12 to 18 inches apart. Larger varieties, like dinnerplate dahlias, appreciate a bit more elbow room, so give them 18 to 24 inches if you have the space.
2. Place the Tuber
Lay the tuber on its side in the bottom of the hole. Some gardeners wonder which way is "up." The goal is to have the eye (the growth point) facing toward the sky. If you cannot find the eye, laying the tuber flat on its side is a safe bet, as the sprout will naturally find its way to the surface.
3. Add a Stake Now
This is one of our favorite simple gardening rules: always put your stake in the ground at the same time you plant the tuber. Most dahlias grow between three and five feet tall and will eventually need support. If you wait until the plant is large to drive a stake into the ground, you might accidentally poke a hole through the tubers growing underneath. Placing the stake now keeps your tubers safe.
4. Cover with Soil
Fill the hole back up with soil. You do not need to pack the soil down tightly; just a gentle firming with your hands is enough. This leaves plenty of air pockets for the roots to breathe.
What to Do Next:
- Pick a sunny afternoon when the soil is dry and crumbly.
- Dig your 4-6 inch holes and space them according to the variety.
- Place tubers horizontally with the eye facing up.
- Drive a sturdy stake into the ground next to the tuber before filling the hole.
The Most Important Rule: Don't Water Yet
This is the part where many new gardeners get nervous. Usually, when we plant something, we immediately give it a big drink of water. With dahlias, you should do the opposite.
Unless your soil is bone-dry and dusty, do not water your dahlias after planting them in the ground. The tuber has enough stored moisture to get the plant started. If you add too much water before the plant has roots and leaves, the tuber can rot. Wait until you see the first green shoots peeking through the soil. Once the plant is a few inches tall, you can begin a regular watering schedule. This simple wait is one of the biggest keys to a healthy dahlia garden.
Growing and Caring for Your Dahlias
Once your dahlias have emerged from the ground, they grow very quickly. Within a few weeks, you will see lush green foliage and sturdy stems.
Watering Correctly
Dahlias like deep, consistent watering once they are established. Instead of a light sprinkle every day, give them a deep soak two or three times a week. This encourages the roots to grow deep into the ground, making the plant more stable. Try to water at the base of the plant to keep the leaves dry, which helps prevent common issues like powdery mildew.
Pinching for More Blooms
If you want your dahlia to be bushy and full of flowers rather than one tall, single stem, you should "pinch" the plant. For a step-by-step guide, see our How to Pinch and Stake Dahlias. When the dahlia is about 12 to 16 inches tall and has several sets of leaves, snip off the very top of the main center stem. This might feel a bit scary at first, but it tells the plant to grow more side branches. More branches mean more flowers!
Feeding Your Plants
Dahlias are "heavy feeders," meaning they use a lot of nutrients to produce their big blooms. You can apply a balanced, water-soluble fertilizer every two to three weeks once the plant is established. Look for a fertilizer where the middle number (phosphorus) is a bit higher than the first number (nitrogen). Too much nitrogen will give you lots of green leaves but very few flowers.
Managing Pests and Challenges
Gardening is a natural process, and sometimes you will run into small challenges. The best approach is to stay observant and act early.
Slugs and Snails
When dahlia shoots are young and tender, they are a favorite snack for slugs. You can protect your plants by using a simple slug bait or by keeping the area around the base of the plant clear of debris where slugs like to hide.
Common Foliage Issues
In late summer, you might notice a white, dusty coating on the leaves. This is called powdery mildew. It is very common and usually occurs when the air is humid and there isn't enough airflow around the plants. To prevent this, make sure your plants are spaced correctly and avoid watering the leaves. If it becomes a problem, your local garden center can recommend a simple spray to help.
Staking and Support
As your dahlias grow, they will get heavy with leaves and flowers. High winds or heavy rain can easily topple a large dahlia plant. This is where those stakes you put in at planting time come in handy.
Use soft twine or garden tape to gently tie the main stem to the stake every foot or so. You want the tie to be firm enough to hold the plant up but loose enough that it doesn't cut into the stem as it grows. Check your ties every few weeks as the plant expands.
Can Dahlias Stay in the Ground Over Winter?
This is one of the most common questions we hear. The answer depends entirely on where you live. Dahlias are hardy in USDA zones 8 through 11. If you are not sure of your growing zone, our Hardiness Zone Map makes it easy to check. In these warm climates, you can leave the tubers in the ground all year long. Simply cut the dead stalks down after the first frost and cover the area with a few inches of mulch to protect them from winter rain.
For Zones 7 and Colder
In most of the United States (zones 3 through 7), the ground freezes deep enough to kill dahlia tubers. If you live in these areas, you have two choices. You can treat your dahlias as annuals and buy fresh tubers from us each spring, or you can read our guide on How to Overwinter Dahlia Tubers.
How to Lift and Store Tubers
If you want to save your tubers for next year, wait until a hard frost has blackened the foliage. This signals the plant to go dormant.
- Cut the stems down to about 4 inches.
- Carefully dig up the tuber clump, being careful not to nick the tubers with your shovel.
- Shake off the excess soil and let them dry in a cool, shaded spot for a day or two.
- Store the tubers in a box filled with peat moss, vermiculite, or wood shavings.
- Keep the box in a cool, dark place (like a basement or crawl space) where temperatures stay between 40°F and 50°F.
Key Takeaway: While the wait for spring can feel long, the reward of seeing your saved tubers sprout again is well worth the effort. Think of winter storage as a nap for your garden favorites.
Enjoying the Harvest
The best part of growing dahlias in the ground is the harvest. Dahlias are "cut and come again" flowers. This means the more you cut them for bouquets, the more the plant will produce.
When cutting dahlias, look for flowers that are almost fully open. Unlike roses or lilies, dahlias do not open much once they are cut. Use a clean pair of snips and place the stems immediately into a bucket of room-temperature water. To help the blooms last as long as possible, change the water in your vase every day.
Designing Your In-Ground Dahlia Garden
Since you are planting in the ground, you have the opportunity to play with garden design. Dahlias come in a staggering range of heights and colors.
Creating Layers
Plant shorter border dahlias at the front of your flower beds.
These varieties usually grow about 12 to 24 inches tall and create a colorful edge. Place the medium-sized decorative dahlias in the middle, and save the tall dinnerplate and cactus varieties for the back of the border. This "stadium seating" arrangement ensures that every flower gets its moment in the sun.
Color Combinations
You can create a cohesive look by sticking to a color palette. For a romantic feel, mix soft pinks, whites, and Café au Lait dahlias. If you prefer a high-energy garden, look for bright oranges, purples, and bicolors. Because dahlias bloom from mid-summer until the first frost, they are perfect for filling in the gaps left by spring-blooming perennials.
A Note on Shipping and Planning
At Longfield Gardens, we want to make sure your gardening experience is as smooth as possible. We ship our dahlia tubers based on your USDA hardiness zone. This means we time the delivery to arrive roughly two weeks before the ideal planting time for your specific area.
When your package arrives, open it immediately to let the tubers breathe. If it is still a bit too cold to plant outside, you can keep the tubers in their shipping material in a cool, dry place until the soil warms up. For more details, see our Shipping Information. Remember that we only ship within the 48 contiguous United States, and we stand behind our 100% quality guarantee. If your tubers arrive damaged or you have questions about their condition, our team is ready to help.
Realistic Expectations
Gardening is a partnership with nature. While we provide premium tubers and the best advice, factors like unexpected heatwaves, unusually wet springs, or local soil variations will all play a role in how your dahlias grow.
If a plant doesn't bloom as early as you expected, remember that some varieties take longer to mature than others. A giant dinnerplate dahlia needs more time to build its massive flowers than a small pompon variety. Patience is a gardener's best friend. The sight of a perfectly formed dahlia bloom in late August is a reminder that the best things are worth the wait.
Conclusion
Growing dahlias in the ground is a simple, joyful way to bring world-class beauty to your own backyard. By focusing on the basics—plenty of sun, well-draining soil, and waiting for the ground to warm up—you are setting yourself up for a spectacular summer of color. Dahlias are generous plants that reward a small amount of effort with an abundance of blooms.
- Wait for warmth: Only plant once the soil is 60°F and frost is gone.
- Dry start: Do not water until you see the first green sprouts.
- Support early: Stake your dahlias at planting time to protect the tubers.
- Enjoy the process: Cut frequently to encourage more flowers and share the joy with friends.
We invite you to explore the wide variety of dahlia shapes and colors available at Longfield Gardens, including our Pretty in Pink Collection. Whether you are a beginner or an experienced grower, there is always something new to discover in the world of dahlias. Start small, follow the steps, and get ready to fall in love with your garden all over again.
FAQ
Can I plant dahlias in the ground if I have heavy clay soil? Yes, you can certainly grow dahlias in clay soil, but you must improve the drainage first. Mix in several inches of compost or well-rotted organic matter to the planting area to help break up the heavy clay. If the area stays very wet, consider planting your dahlias in a slightly mounded row to keep the tubers above the standing water.
How deep should I plant my dahlia tubers in the ground? Dahlia tubers should be planted approximately 4 to 6 inches deep. Lay the tuber horizontally in the hole with the eye (the small growth bud) facing upward. If you cannot find the eye, laying it flat on its side is perfectly fine, as the plant will naturally grow toward the light.
Do I need to water my dahlias as soon as I put them in the ground? No, you should avoid watering your dahlias immediately after planting in the ground unless the soil is extremely dry. The tuber contains enough moisture to begin its growth. Adding extra water before the plant has developed roots can lead to the tuber rotting. Wait until you see green shoots emerging from the soil before starting a regular watering routine.
Will my dahlias come back every year if I leave them in the ground? This depends on your climate. In USDA zones 8 and warmer, dahlias are generally hardy and can stay in the ground year-round with a layer of mulch for protection. In zones 7 and colder, the ground will freeze and kill the tubers. In these colder regions, you must either dig up the tubers and store them indoors for the winter or treat them as annuals and plant new ones each spring.