Introduction
There is nothing quite like the sight of a dahlia in full bloom. These spectacular flowers are the undisputed stars of the late-summer garden, offering an incredible variety of colors, shapes, and sizes. Whether you want dinnerplate dahlias that demand attention or petite border varieties for a tidy splash of color, dahlias provide an abundance of flowers that last until the first frost. We love these plants because they are as generous as they are beautiful, often producing more blooms the more you cut them for bouquets.
At Longfield Gardens, we want to help you experience the joy of growing these rewarding flowers in your own yard. This guide is designed for home gardeners who want clear, practical advice on how to plant and grow dahlias successfully. We will cover everything from selecting the right spot and preparing your soil to the simple care steps that ensure a season full of color. By focusing on a few essential basics, you can enjoy a professional-looking flower garden regardless of your previous experience. For additional guidance, visit our dahlia planting and care guide.
Understanding Dahlia Tubers
Before you get into the soil, it helps to understand what you are planting. Dahlias grow from tubers, which are thickened underground stems that store energy for the plant. They look somewhat like a bunch of small, elongated potatoes joined at a central point called the crown.
When you receive your tubers from us, you might notice they come in different sizes. It is a common gardening myth that a larger tuber produces a larger plant. In reality, a small tuber is just as capable of producing a massive, healthy plant as a large one. The most important part of the tuber is the "eye."
The eye is a small bump or sprout located on the crown, where the tuber meets the stem. This is the point where new growth begins. Sometimes eyes are easy to see, looking like a tiny green or pink nub. Other times, they are dormant and harder to spot. If you cannot see an eye right away, do not worry. Once the tuber is tucked into warm soil, that eye will wake up and begin to grow.
Key Takeaway: Focus on the health of the tuber rather than its size. As long as the tuber is firm and has an intact "neck" connecting it to the crown and an eye, it has everything it needs to thrive.
Choosing the Right Location
Success with dahlias starts with picking the right spot in your yard. These plants are sun-seekers and perform best when they have the energy of the sun to fuel their rapid growth.
Sunlight Requirements
For the most flowers and the strongest stems, plant your dahlias in full sun. This means a spot that receives at least six to eight hours of direct sunlight each day. While they can grow in partial shade, you will likely see fewer blooms and taller, "leggy" stems that struggle to support the weight of the flowers. If you live in an exceptionally hot climate, a little bit of afternoon shade can help prevent the petals from wilting in the most intense heat.
Soil and Drainage
Dahlias are very particular about their "feet" being dry. They need well-draining soil to stay healthy. Drainage simply refers to how quickly water moves through the soil. If you have a spot where puddles linger for hours after a rainstorm, that area is likely too wet for dahlia tubers.
These plants thrive in loose, fertile soil that is rich in organic matter. If your soil is heavy clay or very sandy, you can improve it easily by mixing in a few inches of compost or well-rotted manure before planting. This helps balance the soil texture, allowing it to hold enough moisture for the roots while letting the excess drain away.
Space and Airflow
Dahlias grow quickly and can become quite bushy by mid-summer. Good airflow is essential for keeping the foliage healthy. When choosing a spot, make sure there is enough room for the plants to reach their full width without being crowded by fences or other large perennials.
When to Plant Dahlias
Timing is one of the most important factors when learning how to plant and grow dahlias. Because they are tender perennials, they are very sensitive to cold temperatures.
The simplest rule of thumb is to plant your dahlias at the same time you would plant tomatoes or peppers. In most regions, this is in late spring, well after the danger of frost has passed. The soil needs to be warm—ideally around 60°F. If you plant tubers in cold, wet soil too early in the spring, they may sit dormant and eventually rot before they have a chance to grow.
If you live in a northern climate with a short growing season, you can give your dahlias a head start by "starting" them indoors. About four to six weeks before the last frost date, plant the tubers in pots with damp potting soil and keep them in a warm, sunny spot. By the time the weather warms up, you will have established plants ready to go into the garden. Use the hardiness zone map to learn more about your growing climate.
How to Plant Dahlia Tubers Step-by-Step
Once the weather is warm and your site is ready, it is time to plant. Following these simple steps will give your tubers the best start possible.
1. Dig the Hole
Dig a hole about 4 to 6 inches deep. If you are planting a variety that grows quite tall, such as a dinnerplate or decorative dahlia, space your holes about 18 to 24 inches apart. Smaller border or "gallery" varieties can be spaced closer together, around 12 inches apart. For color-coordinated planting ideas, explore the Dahlia Berry Spritz Collection.
2. Add Support Early
Most dahlias grow to be 3 or 4 feet tall and produce heavy flowers. They need support to keep from toppling over in the wind. The best time to put a stake in the ground is at planting time. Drive a sturdy wooden or metal stake into the ground at the edge of your planting hole. Doing this now ensures you won't accidentally drive the stake through the tuber later in the season.
3. Place the Tuber
Lay the tuber horizontally in the bottom of the hole. If you can see the eye or a small sprout, make sure it is pointing upward toward the sky. If you cannot tell which side is which, laying it flat on its side is a safe bet, as the plant will naturally find its way up.
4. Backfill with Soil
Cover the tuber with soil and gently firm it down with your hands to remove any large air pockets. You do not need to pack it down tightly; just a light press is enough.
5. Hold the Water
This is the most common mistake new dahlia growers make. Do not water your tubers immediately after planting unless the soil is bone-dry. The tuber contains enough moisture to start growing on its own. Adding extra water before the sprout emerges can cause the tuber to rot. Wait until you see the first green shoots breaking through the soil surface before you begin a regular watering routine.
What to do next:
- Check your local frost dates to find the safe planting window.
- Purchase sturdy stakes (bamboo, wood, or coated metal) before planting.
- Prepare your garden beds by clearing weeds and adding a layer of compost.
Essential Care for Growing Dahlias
Once your dahlias have sprouted and are actively growing, they require a bit of regular attention to look their best. While they are not difficult to care for, these simple steps make a big difference in the quality and quantity of your blooms.
Watering Correctly
As the plants grow and the summer heat sets in, dahlias become thirsty. The goal is to keep the soil consistently moist but not soggy. A deep watering two or three times a week is usually better than a light sprinkle every day. Deep watering encourages the roots to grow further down into the soil, making the plant more resilient.
If you are growing dahlias in containers, they will dry out much faster than those in the ground. You may need to water pots every day during the height of summer. Always check the soil first; if the top inch feels dry, it is time to water.
The Power of Pinching
If you want a bushy plant with dozens of flowers rather than one tall stalk with just a few blooms, you must "pinch" your dahlias. This might feel counterintuitive, but it is the best thing you can do for the plant.
When your dahlia is about 12 to 16 inches tall and has four or five sets of leaves, use your fingers or a pair of clean snips to cut off the very top of the center stem. Cut it back to just above the highest set of leaves. This signals the plant to stop growing upward and start growing outward. It will send out side branches, resulting in a much stronger, fuller plant with many more flower buds.
Fertilizing for Blooms
Dahlias are "heavy feeders," meaning they use a lot of nutrients to produce those massive flowers. However, you have to choose the right fertilizer. Avoid fertilizers that are very high in nitrogen (the first number on the package). Nitrogen encourages lots of green, leafy growth but can result in very few flowers.
Instead, look for a fertilizer with a higher middle and last number (phosphorus and potassium), such as a 5-10-10 or a bloom-booster formula. Start fertilizing about a month after planting and continue every three to four weeks until mid-September.
Staking and Tying
As your plants grow, they will need to be tied to the stakes you put in the ground at planting time. Use soft twine or garden ties. Loop the twine around the stake and then loosely around the plant stem. You want to provide support without strangling the plant as the stems thicken. For very large plants, you may need to add a second or third tie higher up as the season progresses.
Managing Pests and Challenges
Gardening always comes with a few guests, and dahlias are no exception. Fortunately, most dahlia problems are easy to manage if you catch them early.
Slugs and Snails
Young dahlia sprouts are a favorite snack for slugs. If you see jagged holes in the new leaves or silver trails on the soil, slugs are likely the culprit. You can use organic slug bait or simply remove them by hand in the early morning. Once the plants are about a foot tall and the stems become tougher, they are less attractive to these pests.
Earwigs and Japanese Beetles
Later in the season, you might find insects nibbling on the flower petals. For Japanese beetles, the easiest method is to knock them into a bucket of soapy water in the morning when they are sluggish. For earwigs, providing good airflow and keeping the area around the base of the plants free of debris can help reduce their hiding spots.
Powdery Mildew
In late summer, when the air is humid, you might see a white, flour-like dust on the leaves. This is powdery mildew. While it rarely kills the plant, it can make the foliage look unattractive. To prevent this, always water at the base of the plant rather than over the leaves. Ensuring your plants have plenty of space for air to move between them is the best defense.
Enjoying the Harvest: Cutting and Deadheading
One of the best things about dahlias is that the more you cut them, the more they bloom. To get the most out of your garden, you should participate in two activities: cutting for bouquets and deadheading.
Cutting for Vases
Dahlias make excellent cut flowers. Unlike roses or lilies, dahlias will not open much once they are cut, so wait to harvest them until the flower is nearly fully open. The best time to cut is in the cool of the morning when the stems are full of moisture. Use sharp, clean pruners and place the stems immediately into a bucket of room-temperature water.
The Importance of Deadheading
Deadheading is the process of removing faded or spent flowers. If you leave old flowers on the plant, it will begin to produce seeds. Once a plant starts making seeds, it thinks its job is done and will stop producing new buds. By snipping off the old flowers, you trick the plant into thinking it still needs to reproduce, so it keeps sending up fresh blooms all the way until the first frost.
When deadheading, do not just pull the petals off. Follow the flower stem back down to where it meets a main branch and make a clean cut there. This keeps the plant looking tidy and encourages new growth from the leaf axils.
Key Takeaway: Regular cutting and deadheading are the keys to a long bloom season. Don't be afraid to take big armfuls of flowers inside; your garden will replace them quickly!
End-of-Season Care
As autumn arrives and the first frost hits, your dahlias will undergo a dramatic change. A hard frost will turn the green foliage black and limp almost overnight. This is the signal that the growing season is over.
In warm climates (USDA zones 8 and warmer), you can often leave dahlia tubers in the ground for the winter. Simply cut the stalks down to a few inches and cover the area with a thick layer of mulch to protect them from occasional cold snaps.
In colder climates (zones 7 and colder), dahlia tubers will freeze and die if left in the ground. To save them for next year, you must "lift" them.
- Cut the stalks down to about 4 inches.
- Carefully dig around the clump with a garden fork, being careful not to nick the tubers.
- Gently lift the clump and shake off the excess soil.
- Let them dry in a frost-free, shaded area for a day or two.
- Store them in a box filled with slightly damp peat moss, vermiculite, or wood shavings in a cool, dark place (like a basement) that stays between 40°F and 50°F.
If you don't want to go through the trouble of storing tubers, it is perfectly fine to treat dahlias as annuals and start fresh with new varieties from Longfield Gardens next spring. You can shop the full dahlia collection when planning your next garden.
Growing Dahlias in Containers
If you have limited space or want to brighten up a patio, many dahlias grow beautifully in pots. This is an excellent option for gardeners with heavy, poorly draining soil.
Choose the Right Pot
A single dahlia tuber needs a container that holds at least 2 to 5 gallons of soil, depending on the variety's size. Ensure the pot has large drainage holes at the bottom. Since dahlias can become top-heavy, a heavy ceramic or terra cotta pot is often a better choice than lightweight plastic.
Use Quality Potting Mix
Do not use garden soil in containers; it is too heavy and will not drain well. Use a high-quality, peat-based potting mix. You can mix in a little bit of slow-release fertilizer at planting time to give the plant a steady supply of nutrients.
Care for Container Dahlias
Potted dahlias need more frequent watering and fertilizing than those in the ground. Because the roots are confined, they cannot search for moisture deep in the earth. In the heat of summer, plan on watering daily. Fertilize with a liquid bloom-booster every two weeks to keep the flowers coming.
Summary of Success
Growing dahlias is one of the most satisfying projects a gardener can undertake. From a single, funny-looking tuber comes a lush, green bush topped with architectural blossoms that seem too perfect to be real. By getting the basics right—sun, drainage, and timing—you set the stage for a spectacular show.
At Longfield Gardens, we take pride in providing high-quality tubers that are ready to perform. We stand behind our plants with a 100% quality guarantee. We want your gardening experience to be successful and enjoyable. If your items arrive damaged or there is a variety mix-up, please contact our team so we can make it right. We also provide support throughout the season if you have questions about performance.
Remember that gardening is a partnership with nature. Every season is different, and every yard has its own unique microclimate. Be patient, observe your plants, and enjoy the process. The reward of a vase full of home-grown dahlias is well worth the effort.
Conclusion
Dahlias are a true gift to the summer garden, providing endless color and beauty with just a little bit of help from you. By choosing a sunny spot, waiting for warm soil, and remembering to pinch your plants, you can grow a stunning display that will be the envy of the neighborhood. Whether you are a seasoned gardener or a total beginner, these plants offer a high return on your investment of time and care.
- Plant in full sun for the strongest stems and most flowers.
- Wait for warm soil before tucking your tubers into the ground.
- Pinch the center stem when the plant is 12 inches tall for a bushier habit.
- Deadhead regularly to keep the blooms coming until the first frost.
Growing dahlias is a journey of discovery. With so many colors and forms to choose from, you can create a unique garden landscape every single year.
We invite you to explore the different dahlia varieties we offer and start planning your most colorful season yet. With a little bit of sunshine and these simple steps, you'll be well on your way to a garden full of spectacular dahlias.
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 about 60°F. A good rule of thumb is to plant them at the same time you would put tomato plants in the garden. For additional seasonal information, review the shipping information before ordering.
Why are my dahlias growing tall but not blooming?
This is usually caused by too much nitrogen in the soil or not enough sunlight. Ensure your dahlias get at least 6 to 8 hours of sun and use a fertilizer that is higher in phosphorus and potassium rather than nitrogen to encourage flower production. The dahlia care resource offers additional troubleshooting guidance.
Do I need to water my dahlia tubers as soon as I plant them?
No, it is best to wait until you see the green sprouts emerging from the soil before you start a regular watering schedule. The tubers contain enough stored moisture to begin growing, and excessive water early on can cause them to rot.
How do I get my dahlias to have more flowers?
The two best ways to increase blooms are pinching and deadheading. Pinch the center stalk when the plant is about 12 inches tall to encourage branching, and remove faded flowers throughout the season so the plant continues to produce new buds.
