Introduction
There is nothing quite like the excitement of seeing your first dinnerplate dahlia begin to unfurl in midsummer. These spectacular flowers come in an almost endless variety of colors and shapes, making them a favorite for home gardeners who want to add high-impact beauty to their landscapes. Whether you are dreaming of a dedicated cutting garden or simply want a few stunning accents in your flower beds, you might be wondering: can dahlias grow in the ground?
The short answer is a resounding yes. While many people grow these flowers in containers or raised beds, dahlias are perfectly at home in the garden soil. Growing them directly in the ground often allows the plants to reach their full potential, producing larger blooms and more robust stems. At Longfield Gardens, we want to help you feel confident as you plan your garden, ensuring you get the most enjoyment from every tuber you plant.
This guide is designed for anyone who wants to transition their dahlia-growing to the open ground. We will cover everything from choosing the right spot and preparing your soil to the simple steps for planting and season-long care. By focusing on a few gardening basics, you can turn any sunny patch of earth into a blooming paradise.
Growing dahlias in the ground is one of the most rewarding ways to garden, providing you with armloads of fresh flowers from midsummer right up until the first frost.
Why Dahlias Thrive in the Ground
When you choose to plant dahlias directly in the soil, you are giving them the freedom to develop an extensive root system. In a pot, a plant’s roots are limited by the size of the container. In the ground, those roots can spread out and go deep, which helps the plant stay hydrated and find the nutrients it needs to produce those famous, oversized blooms.
Planting in the ground also offers better temperature stability for the tubers. Soil in the ground stays cooler during the heat of a summer afternoon compared to the soil in a plastic or ceramic pot. This consistent environment helps the plant stay focused on growing and blooming rather than struggling with heat stress. If you have the space, the ground is often the easiest place to achieve the tall, lush look that dahlias are known for.
Key Takeaway: Ground planting provides more room for roots to grow and offers a more stable environment, leading to taller plants and more abundant flowers.
Choosing the Perfect Spot
The first step toward success is finding a location that meets the specific needs of your plants. Dahlias are sun-loving flowers that need plenty of energy to fuel their rapid growth and heavy blooming. For a fuller checklist, see 8 Tips for Growing Better Dahlias.
Sunlight Requirements
For the best results, pick a spot that receives at least six to eight hours of direct sunlight every day. Full sun is the "battery" that powers the dahlia’s growth. While they can grow in areas with a bit of afternoon shade, they will produce fewer flowers and may develop "leggy" stems that are more prone to falling over. If you live in an exceptionally hot climate, morning sun and a little bit of dappled shade in the late afternoon can be helpful, but for most US gardeners, the sunnier the better.
Drainage is Essential
Good drainage is one of the most important factors for dahlia health. Drainage simply refers to how fast water leaves the soil after a rainstorm or watering. Dahlias have fleshy tubers that can be sensitive to sitting in soggy earth. Before you plant, observe your chosen spot after a heavy rain. If water pools there for more than an hour or two, the drainage may be too slow.
If you have heavy clay soil that stays wet, you don't have to give up on ground planting. You can improve the spot by mixing in organic matter or by slightly mounding the soil where you plant each tuber. This creates a small "hill" that helps excess water run away from the center of the plant.
What to do next:
- Observe your yard for a full day to find the sunniest areas.
- Avoid spots near large trees or shrubs that might compete for water and nutrients.
- Check the soil after a rain to ensure it doesn't stay swampy.
- Identify a location that is sheltered from very strong winds if possible.
Preparing Your Soil for Planting
You don't need "perfect" soil to grow beautiful dahlias, but a little bit of preparation goes a long way. Most garden soil can be improved with a few simple additions that make it easier for roots to move and air to circulate.
Understanding Your Soil Type
If your soil feels sticky and holds its shape when you squeeze it into a ball, you likely have clay soil. Clay is rich in nutrients but can be very dense. If your soil feels gritty and falls apart quickly, it is sandy. Sandy soil drains well but doesn't hold onto water or nutrients very long.
The solution for both types of soil is the same: add organic matter. Mixing in a few inches of high-quality compost or well-rotted leaf mold will transform your soil. In clay, compost helps break up the tiny particles so water can flow through. In sandy soil, compost acts like a sponge, helping the earth hold onto the moisture your dahlias need.
Simple Soil Prep Steps
Start by clearing away any weeds or grass from your planting area. Use a garden fork or spade to loosen the soil to a depth of about 12 inches. This "fluffing" of the soil makes it much easier for the young dahlia roots to expand once the tuber sprouts. Spread a two-inch layer of compost over the surface and gently work it into the top few inches of soil. You don't need to overwork it; the earthworms and other soil life will finish the job for you.
Timing Your Planting
One of the most common mistakes in gardening is rushing to get plants in the ground before the weather is truly ready. With dahlias, timing is more important than almost any other "trick."
Wait for Warm Soil
Dahlias are native to warm climates, and they do not like cold soil. Even if the air feels warm in the afternoon, the ground can stay chilly well into late spring. A good rule of thumb is to wait until all danger of frost has passed and the soil temperature is at least 60°F. In most parts of the US, this is the same time you would plant tomatoes or peppers. For shipping timing by region, see Shipping Information.
If you plant too early into cold, wet soil, the tuber may sit dormant for a long time or struggle to get started. Waiting for the right window ensures the plant takes off quickly and grows vigorously.
USDA Hardiness Zones
At Longfield Gardens, we ship our tubers according to your USDA hardiness zone. This helps ensure they arrive at the ideal time for your specific climate. Most gardeners receive their order about two weeks before the typical planting time for their area. This gives you a little time to prepare your garden beds so you are ready to go as soon as the weather settles.
Key Takeaway: Patience pays off. Planting your dahlias in warm soil (at least 60°F) after the last frost leads to much faster growth and healthier plants.
Step-by-Step Guide to Planting in the Ground
Once your soil is prepared and the weather is warm, it’s time to get your tubers in the ground. Following a few simple steps for depth and spacing will set your garden up for a successful season. If you want a broader set of planting basics, 8 Tips for Growing Better Dahlias is a helpful companion guide.
Digging the Hole
Dig a hole that is about 4 to 6 inches deep. If you are planting a single tuber, the hole doesn't need to be very wide—just enough to accommodate the length of the tuber. If you have a larger clump of tubers, make the hole wide enough so they can lay flat without being crowded.
Positioning the Tuber
Look for the "eye" of the tuber. The eye is a small bump or a new green sprout located at the "neck" where the tuber meets the old stem. Lay the tuber horizontally (flat) in the hole with the eye facing upward. If you can’t clearly see an eye, don't worry—just lay the tuber flat, and the sprout will find its way to the surface.
Spacing Your Plants
Dahlias need plenty of elbow room. As they grow, they become large, bushy plants that need good airflow to prevent issues like powdery mildew.
- Border or bedding dahlias: Space them 12 to 18 inches apart.
- Medium varieties: Space them 18 to 24 inches apart.
- Large dinnerplate varieties: Space them at least 24 to 36 inches apart.
Covering and Initial Care
Fill the hole back in with the soil you removed. Gently firm it down with your hands, but do not pack it tightly. Here is a very important tip for beginners: do not water your dahlias immediately after planting. There is usually enough moisture in the ground to get them started. Watering too much before the plant has roots and a sprout can lead to rot. Wait until you see the first green shoots peeking through the soil before you begin a regular watering schedule.
Supporting Your Dahlias
Because many dahlia varieties grow quite tall and produce very heavy flowers, they need a little bit of help staying upright. Ground-grown dahlias are particularly prone to "flopping" during summer thunderstorms or heavy winds.
When to Stake
The best time to put a stake in the ground is at the moment you plant the tuber. If you wait until the plant is large, you might accidentally drive the stake through the tubers underground. By placing the stake early, you know exactly where it is in relation to the plant.
Types of Support
For most home gardens, a sturdy wooden or bamboo stake is perfect. You can also use tall metal stakes or even tomato cages for smaller varieties. As the plant grows, use soft twine or strips of old fabric to loosely tie the main stem to the stake every 12 to 18 inches. Make sure the ties are loose enough to allow the stem to thicken as the plant matures.
Key Takeaway: Stake your dahlias at planting time to avoid damaging the tubers later. Regular ties every foot or so will keep your tall varieties standing proud.
The Power of Pinching
If you want the most flowers possible, there is one simple technique you should use: pinching. Pinching sounds like it might be hard on the plant, but it actually encourages the dahlia to become bushier and produce more stems.
When your dahlia plant is about 12 to 16 inches tall and has about four sets of leaves, use your fingers or a clean pair of snips to remove the very top of the center stem. By removing this "terminal bud," you signal the plant to stop growing only upward and start sending out side branches from the leaf nodes below. This results in a much stronger, more balanced plant with many more flower buds.
While it might feel strange to cut off the top of a healthy young plant, the rewards in mid-to-late summer are well worth it. You will end up with a lush bush covered in blooms rather than one single, tall stalk.
Watering and Feeding
Once your dahlias have sprouted and are about six inches tall, it is time to start a consistent care routine. Proper watering and feeding are the secrets to those vibrant, healthy leaves and constant flowers.
Water Deeply, Not Constantly
Instead of giving your plants a little bit of water every day, it is better to give them a deep soaking once or twice a week. This encourages the roots to grow deep into the ground to find moisture, making the plant more resilient. During the heat of midsummer, you may need to water more frequently, especially if your soil is sandy. Aim the water at the base of the plant rather than over the leaves to help keep the foliage dry.
Providing Nutrients
Dahlias are "heavy feeders," meaning they use a lot of energy to grow so fast and produce so many blooms. If you added compost at planting time, your plants have a great start. To keep them going throughout the season, you can apply a balanced, water-soluble fertilizer every three to four weeks. Look for a fertilizer where the middle and last numbers (phosphorus and potassium) are equal to or higher than the first number (nitrogen). Too much nitrogen can lead to lots of green leaves but very few flowers.
Mulching the Ground
Applying a two-inch layer of mulch around the base of your dahlias is a great way to keep the ground cool and moist. Use shredded bark, straw, or clean grass clippings. Just be sure to keep the mulch a few inches away from the main stem to prevent any moisture buildup against the stalk.
Harvesting and Deadheading
The more you cut your dahlias, the more they will bloom. This is one of the best parts of growing these flowers in the ground—you can harvest beautiful bouquets every week and the plant will just keep producing.
Cutting for Vases
When you want to bring flowers inside, cut them in the early morning when they are fully hydrated. Choose blooms that are almost fully open, as dahlias do not open much once they are cut. Use sharp, clean snips and place the stems immediately into a bucket of room-temperature water.
The Importance of Deadheading
If you don't cut all the flowers for bouquets, you must "deadhead" the ones that fade on the plant. Deadheading is simply the process of removing spent flowers. If you leave the old flowers on the plant, it will stop producing new buds and start putting its energy into making seeds. By snipping off the old blooms, you "trick" the plant into thinking it still needs to make more flowers.
When deadheading, don't just snip the flower head. Cut the stem back to the next set of leaves to keep the plant looking tidy and encourage new growth from that point.
What Happens in the Winter?
Since dahlias are grown from tubers, they behave differently than many other perennials. Whether or not they can stay in the ground during the winter depends entirely on where you live. For help matching planting times to your climate, Longfield Gardens organizes shipping around hardiness zones.
In Warm Climates (Zones 8-11)
In the southern and coastal parts of the US, dahlia tubers can often stay in the ground all year round. The ground doesn't freeze deep enough to damage the tubers. In these areas, you can simply cut the stalks back to a few inches above the ground after the first frost and cover the spot with a thick layer of mulch to provide a little extra protection.
In Cold Climates (Zones 7 and lower)
In most of the country, the ground freezes during the winter, which will cause dahlia tubers to turn to mush. If you live in these zones, you have two choices:
- Treat them as annuals: Enjoy the massive display of flowers all summer, and then let the frost take the plants at the end of the season. You can then start fresh with new varieties from us next spring.
- Lift and store: After the first frost kills the foliage, you can carefully dig up the tubers, wash off the soil, and store them in a cool, dark, frost-free place (like a basement) until next spring.
Regardless of your zone, the gardening process is the same for the entire growing season. The choice to save the tubers is a personal one based on your time and storage space.
Key Takeaway: Dahlias are winter-hardy only in warm climates. If you live in a cold region, you must either dig up the tubers for winter or replant fresh ones each spring.
Keeping Your Garden Healthy
Dahlias are generally very easy to care for, but like any plant, they can occasionally run into a few hurdles. Growing them in the ground makes them quite resilient, but it's good to know what to watch for.
Slugs and Snails
When dahlia sprouts are young and tender, they are a favorite snack for slugs. You can protect your new plants by keeping the area free of debris and using simple, pet-friendly slug deterrents available at any garden center. Once the plants are about a foot tall, they are usually strong enough that slugs are no longer a major concern.
Powdery Mildew
In the late summer, especially if the weather is humid, you might see a white, dusty coating on the leaves. This is powdery mildew. You can help prevent this by giving your plants plenty of space for airflow and by watering at the base of the plant instead of on the leaves. If it becomes a problem, a simple spray of water mixed with a little bit of horticultural oil or neem oil can help manage it.
Realistic Expectations
Gardening is a partnership with nature. Some years the weather will be perfect, and your dahlias will reach six feet tall by August. Other years might be exceptionally rainy or dry, and the plants may grow a bit more slowly. By getting the basics of sun, drainage, and spacing right, you are giving your dahlias the best possible foundation to handle whatever the season brings.
Summary of Ground-Planting Success
Growing dahlias in the ground is an achievable and rewarding project for any gardener. To ensure you get the best results, keep these core steps in mind:
- Sun and Drainage: Choose a spot with 6+ hours of sun and soil that doesn't stay soggy.
- Soil Prep: Add compost to help with drainage and nutrients.
- Wait for Warmth: Don't plant until the soil is 60°F and the danger of frost is gone.
- Planting Depth: Place tubers 4 to 6 inches deep and lay them flat.
- Hold the Water: Don't water until you see the first green sprouts.
- Support: Stake tall varieties at planting time.
- Pinch and Deadhead: These two steps are the secrets to a bushier plant with more flowers.
Conclusion
Can dahlias grow in the ground? Absolutely. In fact, many of the most stunning dahlia displays in the world are grown this way. By giving your plants the space, sun, and drainage they need, you are setting the stage for a spectacular summer show. Whether you are planting a single Thomas Edison for its deep purple blooms or a whole row of Cafe au Lait for a romantic cutting garden, the ground provides the perfect home for these garden stars.
At Longfield Gardens, we take pride in providing high-quality tubers that are ready to thrive in your backyard. We have tested many varieties in our own trial gardens to ensure they perform beautifully for home gardeners across the country. Remember, gardening is meant to be a joyful experience. Each year brings new lessons and new beauties to discover.
Ready to start your own dahlia journey? Visit our spring-planted bulbs to explore our collection of premium dahlia tubers and find the perfect colors for your garden.
"There is a unique kind of peace found in a dahlia garden at sunrise, with the dew still on the petals and the promise of a dozen new blooms by noon."
FAQ
When is the best time to plant dahlias in the ground?
The best time to plant is in late spring, once all danger of frost has passed and the soil has warmed to about 60°F. This is usually around the same time you would plant other warm-weather favorites like tomatoes or zinnias. Planting in warm soil helps the tubers sprout quickly and grow more vigorously.
Do I need to water my dahlias as soon as I plant them?
No, it is actually better to wait until you see the first green shoots peeking through the soil before you start a regular watering routine. Tuber-grown plants like dahlias have enough stored energy and moisture to get started on their own. Watering too early can lead to rot before the roots have a chance to develop.
How deep should I plant dahlia tubers in the garden?
Dahlia tubers should be planted about 4 to 6 inches deep. Dig a hole, lay the tuber horizontally (flat) at the bottom, and cover it back up with soil. If you are planting in heavy clay soil, sticking to the shallower end (4 inches) can help the sprout reach the surface more easily.
Can I leave my dahlias in the ground over winter?
This depends on your USDA hardiness zone. In zones 8 through 11, where the ground does not freeze deeply, you can often leave them in the ground with a protective layer of mulch. In zones 7 and colder, the freezing temperatures will damage the tubers, so you must either dig them up to store indoors or replant fresh tubers the following spring.
