Introduction
There is a unique kind of magic that happens in late summer when dahlias begin to bloom. These plants are the undisputed stars of the garden, offering a variety of colors, shapes, and sizes that few other flowers can match. Whether you are looking for massive dinnerplate dahlias the size of a frisbee or tidy, geometric pompons, dahlias provide a rewarding experience that makes every bit of garden space feel like a professional floral studio.
At Longfield Gardens, we believe that everyone should feel the excitement of harvesting their first armload of fresh-cut dahlias. While they might look like exotic, high-maintenance plants, they are actually quite straightforward to grow if you follow a few basic steps. We focus on providing the highest quality tubers to ensure your gardening journey starts on the right foot.
This guide is designed for home gardeners who want to learn the most effective ways to plant and care for these spectacular flowers. For a visual walkthrough, see How to Plant Dahlias.
Growing dahlias is one of the most satisfying ways to bring lasting beauty to your landscape from midsummer all the way through the first frost.
Understanding Your Dahlia Tubers
Before you get your shovels ready, it is helpful to understand what exactly you are planting. Dahlia tubers are thickened underground parts of the stem used for food storage. If you have ever seen a bunch of potatoes or ginger root, you have a good idea of what a dahlia tuber looks like.
When you receive your order from us, you may see a single tuber or a small clump. Both are equally capable of producing a magnificent plant. The size of the tuber does not determine the size of the flower; a small tuber can produce a five-foot plant just as easily as a large one. What matters most is the presence of an "eye."
Identifying the Eye
The eye is a small bump or sprout located on the "crown" of the tuber, which is the area where the tuber connects to the old stem. This is where the new growth will emerge. Sometimes eyes are very easy to see, looking like tiny pink or green nubs. Other times, they are dormant and harder to spot.
If you cannot find the eye, do not worry. You can place your tubers in a warm, bright spot for a few days to "wake them up" before planting. As long as the tuber is firm and the neck (the narrow part connecting the tuber to the crown) is intact, the plant has everything it needs to grow.
Tuber Care Before Planting
Once your tubers arrive from our facility in Lakewood, New Jersey, open the box immediately. If it is still too cold to plant outside, keep them in a cool, dark, and frost-free place. A basement or a garage that stays around 40–50°F is ideal. If the packing material feels very dry, a tiny mist of water can help, but avoid making them wet, as moisture is the enemy of a dormant tuber. For more details on delivery timing, see our shipping information.
Key Takeaway: A healthy dahlia plant grows from a firm tuber with at least one viable eye. Tuber size is less important than the health of the crown and the neck.
Choosing the Best Spot in Your Garden
Success with dahlias starts with the "right plant, right place" rule. Because these plants are native to the high plains of Mexico, they have specific preferences for light and soil that mimic their original home.
Sunlight Requirements
Dahlias are sun-lovers. To produce those famous, abundant blooms, they need at least six to eight hours of direct sunlight every day. In cooler northern climates, full sun all day is best. If you live in a very hot southern region, your dahlias will appreciate a bit of dappled afternoon shade to protect them from the most intense heat of the day.
If they are planted in too much shade, the plants will become "leggy," meaning they grow tall and thin as they stretch toward the light. Shaded plants also produce fewer flowers and weaker stems that are more likely to flop over.
Soil and Drainage
The most important factor for tuber health is drainage. "Drainage" is simply a measure of how quickly water moves through your soil. Dahlias do not like "wet feet." If the soil stays soggy for too long, the tubers can rot before they even have a chance to sprout.
The ideal soil is rich, crumbly, and full of organic matter. If you have heavy clay soil that stays wet after a rain, consider planting in raised beds or amending the area with compost or peat moss to improve the texture. Sandy soil is also fine, though it may require more frequent watering and fertilizing once the plants are established. For a broader overview, read All About Dahlias.
Wind Protection
Because dahlias can grow quite tall and have heavy flower heads, they can act like sails in a strong wind. If possible, choose a spot that is somewhat sheltered from high winds, such as near a fence or on the leeward side of a building. However, ensure there is still plenty of air circulation around the plants to keep the foliage healthy.
What to do next:
- Observe your garden for a full day to find the spots that get 6+ hours of sun.
- Test your drainage by digging a small hole and filling it with water; it should drain away within an hour.
- Clear away any weeds or grass from a 2-foot diameter circle for each plant.
Timing Your Planting
In gardening, timing beats tricks. Planting your dahlias too early is one of the most common mistakes. Because dahlia tubers are sensitive to cold and prone to rot in cold, wet soil, patience is a virtue.
The Soil Temperature Rule
Wait to plant your dahlias until the soil has warmed up to about 60°F. A good rule of thumb is to plant them at the same time you would plant tomatoes or peppers. If the ground is still cold to the touch, it is too early.
The Frost Factor
Dahlias are not frost-hardy. You must wait until the danger of a spring frost has completely passed. Depending on your USDA hardiness zone, this could be anywhere from March to June. If a late frost is predicted after you see green shoots emerging, you can protect them by covering them with a frost blanket or even an empty bucket overnight.
Getting a Head Start
If you live in a region with a short growing season, you can start your tubers indoors about four to six weeks before the last frost. Plant them in pots with potting soil and place them in a warm, sunny window. This gives the plants a head start so they can begin blooming earlier in the summer. When the weather warms up, you can transplant the whole root ball into the garden.
Key Takeaway: For the best results, wait for warm soil and a frost-free forecast. Planting dahlias is a marathon, not a sprint, and waiting for the right conditions leads to faster, healthier growth.
Preparing the Soil for Success
Good soil preparation sets the stage for a season of abundance. You don't need a degree in soil science to get this right; you just need to focus on a few basics.
Adding Organic Matter
Dahlias are "heavy feeders," which means they use a lot of nutrients to create those spectacular flowers. Before planting, mix some well-rotted compost or aged manure into the top few inches of your soil. This improves the soil structure and provides a slow-release source of nutrients.
Fertilizer Basics
While compost is great, many gardeners also use a balanced fertilizer at planting time. Look for a fertilizer where the three numbers on the bag (Nitrogen, Phosphorus, and Potassium) are relatively equal, or one that is slightly lower in Nitrogen. Too much Nitrogen early on can encourage lots of green leaves but very few flowers. Always follow the label instructions for application rates to keep your plants healthy.
Soil pH
Dahlias prefer soil that is slightly acidic to neutral (a pH of about 6.5 to 7.0). If you are unsure about your soil's pH, your local county extension service can provide a simple soil test. For most home gardens, however, simply adding compost is enough to keep the pH in a healthy range.
How to Plant: Step-by-Step
Once the soil is warm and the site is ready, it is time to get the tubers in the ground. Following these steps ensures your dahlias have the space and depth they need to thrive.
Digging the Hole
Dig a hole that is about 4 to 6 inches deep. If you are planting several dahlias, space the holes about 12 to 24 inches apart. Smaller border varieties and pompons can be closer together, while giant dinnerplate varieties need at least two feet of space to allow for air circulation and room to grow.
Placing the Tuber
Lay the tuber horizontally in the bottom of the hole. If you can see the eye or a sprout, point it upward, but don't worry if you can't tell which end is which. The plant is smart enough to find its way to the surface. Laying it flat is the most natural position for the tuber and helps it develop a strong root system.
Filling the Hole
Cover the tuber with soil, but do not pack it down too tightly. You want the soil to be firm enough to hold the tuber in place but loose enough for the tender new shoots to push through easily.
What to do next:
- Dig holes 4–6 inches deep and 18–24 inches apart.
- Place the tuber horizontally in the hole.
- Cover with loose soil and mark the spot with a label so you don't accidentally step on it.
The Critical "No-Water" Rule
This is perhaps the most important tip for planting dahlias: Do not water your tubers immediately after planting.
This often feels counterintuitive to gardeners who are used to watering in new transplants. However, a dormant dahlia tuber does not have a root system yet. It cannot "drink" the water you give it. If the soil is too wet during this dormant phase, the tuber is very likely to rot.
There is usually enough natural moisture in the soil to trigger the tuber to start growing. Wait until you see the first green shoots poking through the soil surface before you start a regular watering routine. The only exception is if you live in an extremely hot, arid climate where the soil is bone-dry; in that case, a very light initial watering is okay, but keep it minimal.
Key Takeaway: Patience in watering is vital. Wait for green growth to appear above the ground before you reach for the watering can.
Supporting Your Plants
Most dahlias grow quite tall and produce large, heavy flowers. Without support, a summer rainstorm or a gust of wind can easily snap the stems. It is much easier to provide support at the time of planting than to try to fix a flopping plant later. For a complete walkthrough, see How to Stake Dahlia Tubers.
Staking
A sturdy wooden or metal stake is the traditional choice. Drive a 4- to 5-foot stake into the ground about 2 inches away from where you planted the tuber. Doing this at planting time prevents you from accidentally driving the stake through the tuber later. As the plant grows, use soft twine or garden ties to gently secure the main stem to the stake every 12 inches.
Tomato Cages
For smaller or mid-sized dahlia varieties, a heavy-duty tomato cage works perfectly. Simply place the cage over the planting spot. As the dahlia grows, the branches will grow through the wires, which provide support from all sides. This is a great "low-maintenance" option for home gardeners.
Corralling
If you are planting a long row of dahlias, you can use a method called "corralling." Drive a t-post or heavy stake at each corner of the bed and every 6 to 8 feet along the sides. Run several levels of strong twine around the perimeter of the posts to create a "fence" that keeps the plants from leaning outward.
The Magic of Pinching
If you want the most flowers possible, you should pinch your dahlia plants. Pinching is a simple pruning technique that encourages the plant to branch out rather than growing as one single, tall stalk.
When to Pinch
Wait until your dahlia plant is about 12 inches tall and has four or five sets of leaves.
How to Pinch
Locate the center growing tip—the very top of the main stem. Use a pair of clean garden snips or your fingers to snip or "pinch" off the top 2 to 3 inches of the center stem, just above the highest set of leaves.
Why It Works
By removing the main growing point, you signal the plant to send its energy to the "axils" (the spots where the leaves meet the stem). This results in a bushier plant with more stems, which ultimately means many more flowers for you to enjoy. While it can feel a little scary to cut off the top of a healthy plant, the results are well worth it.
Key Takeaway: Pinching your dahlias when they are 12 inches tall transforms a single-stalk plant into a lush, multi-stemmed bush filled with blooms.
Caring for Your Dahlias Through the Season
Once your dahlias are established and growing vigorously, their needs change. Proper watering and feeding will keep the blooms coming until the first frost.
Water Correctly, Not Constantly
Once the plants are a foot tall, they need regular water. The rule is "deep, then let it dry a bit." Instead of a light daily sprinkle, give them a deep soaking two or three times a week. This encourages the roots to grow deep into the soil.
If you are growing dahlias in containers, they will dry out much faster and may need water every day during the heat of summer. Always check the soil moisture with your finger; if the top inch is dry, it is time to water.
Fertilizing for Blooms
After the plants are established, you can feed them every 3 to 4 weeks with a water-soluble fertilizer. To encourage flowers, choose a fertilizer that is higher in Phosphorus (the middle number) and Potassium (the last number), and lower in Nitrogen. Avoid high-nitrogen "lawn" fertilizers, as these will give you giant green bushes with very few flowers.
Deadheading
To keep the plant producing new flowers, you must "deadhead." This simply means cutting off the faded blooms before they start to form seeds. When you cut a flower, don't just snip the head off; cut the stem back to a point where it meets a leaf or another branch. This keeps the plant looking tidy and encourages more long-stemmed flowers to grow.
Growing Dahlias in Containers
If you don't have a large garden plot, you can still enjoy dahlias by growing them in pots. This is an excellent way to brighten up a porch, patio, or balcony.
Choosing the Right Pot
Dahlias need room to grow. For most varieties, a 5-gallon container is the minimum size required for a single plant. Ensure the pot has plenty of drainage holes in the bottom. If you are growing smaller "border" dahlias, you can use slightly smaller pots.
Potting Mix
Use a high-quality potting soil rather than garden soil. Potting soil is specially formulated to be light and well-draining, which is essential for tuber health in a container. You can mix in a little bit of slow-release fertilizer at planting time to give the plant a steady supply of nutrients.
Container Care
Containers dry out and lose nutrients faster than the ground. Be prepared to water more frequently and fertilize every two weeks. Because pots can be top-heavy when the dahlia is in full bloom, you may need to secure the pot or use a heavy ceramic container to prevent it from tipping over in the wind.
Managing Common Garden Visitors
Gardening is a shared experience with nature, and occasionally, a few uninvited guests might show up. The key is to catch them early and use simple, effective methods to manage them.
Slugs and Snails
When dahlia shoots are young and tender, slugs and snails find them delicious. You can protect your plants by using organic slug bait or simply checking the plants in the early morning and removing the slugs by hand. Once the plants are a foot tall and the stems become tougher, slugs are much less of a problem.
Japanese Beetles
In midsummer, Japanese beetles may visit your dahlia blooms. The easiest and most effective way to manage them is to knock them into a bucket of soapy water. It is best to do this in the morning when the beetles are less active.
Powdery Mildew
In late summer, you might notice a white, flour-like dust on the leaves. This is powdery mildew, a common fungus. To prevent it, ensure your plants have plenty of space for air to circulate. Watering at the base of the plant rather than over the leaves also helps keep the foliage dry and healthy.
Realistic Expectations for Your Dahlia Season
While we provide high-quality tubers and these steps offer a clear path to success, it is important to remember that every garden is a unique ecosystem. Your results will naturally vary based on your local microclimate, the specific weather patterns of the year, and your soil type.
Some years may be exceptionally hot, which can cause dahlias to take a "break" from blooming until the cooler nights of autumn arrive. In other years, a particularly rainy spring might mean you need to be extra vigilant about drainage. These variations are part of the adventure of gardening.
If a plant doesn't perform exactly as expected in its first year, don't be discouraged. Gardening is a process of learning and observing. At Longfield Gardens, we stand behind our 100% quality guarantee. If your tubers arrive damaged or if there is a performance issue in the first growing season, our customer service team is here to help with solutions like replacements or store credit.
Conclusion
Planting dahlias is one of the most rewarding projects a gardener can undertake. By choosing a sunny spot with great drainage, waiting for the soil to warm, and giving your plants the support and pinching they need, you set yourself up for a spectacular show of color. These flowers are not just plants; they are an invitation to spend more time outdoors and to share beauty with your friends and neighbors.
- Wait for 60°F soil and no risk of frost before planting.
- Plant tubers 4–6 inches deep and lay them horizontally.
- Do not water until you see green growth.
- Pinch the center stem when the plant reaches 12 inches tall.
At Longfield Gardens, we are honored to be a part of your garden's story. We work with trusted growers in regions like Holland to ensure that the tubers we ship from our New Jersey facility are healthy, true to variety, and ready to thrive in your yard.
Your next step is to choose a sunny spot in your garden and mark your calendar for planting day. Browse our Dahlia Collections when you are ready to start planning your garden.
FAQ
How deep should I plant dahlia tubers?
Dahlia tubers should be planted about 4 to 6 inches deep. This depth provides a stable foundation for the growing plant and protects the tuber from temperature fluctuations while keeping it close enough to the surface for shoots to emerge easily.
Can I plant dahlias in the shade?
Dahlias need at least 6 to 8 hours of direct sunlight to produce flowers and maintain strong stems. While they can survive in partial shade, they will often become leggy, produce very few blooms, and be more susceptible to disease.
Do I need to soak dahlia tubers before planting?
No, it is not necessary or recommended to soak dahlia tubers. Unlike some other bulbs, dahlia tubers are prone to rot if they get too wet before they have active roots and shoots. The natural moisture in the soil is usually enough to start the growth process.
When will my dahlias start blooming?
Most dahlias begin to bloom about 8 to 12 weeks after planting. This typically means you will see your first flowers in mid-to-late July, with the peak blooming season occurring in August and September when the nights begin to cool down. If you want the biggest display, start with our dinnerplate varieties.
