Introduction
Imagine walking into your garden in late August and being greeted by flowers the size of dinner plates in colors so vibrant they almost look painted. Dinnerplate dahlias are the undisputed stars of the late-summer landscape, offering an incredible variety of shapes, sizes, and hues. Whether you are growing petite pompons or massive decorative types, these plants provide a spectacular payoff for very little effort.
At Longfield Gardens, we know that dahlias can feel a bit different from other spring-planted bulbs because they grow from tubers. However, caring for them is a straightforward and rewarding process once you understand their basic needs. We want to help you feel confident as you tend to these garden favorites throughout the season.
This guide will walk you through every step of how to take care of a dahlia plant, from the moment you receive your tubers to the final harvest of the year. We will cover site selection, planting, maintenance, and how to keep your dahlias blooming until the first frost. Growing healthy, vibrant dahlias is an achievable goal for every gardener when you follow these simple care steps.
Receiving and Storing Your Dahlia Tubers
The journey of caring for a dahlia plant begins before the tuber ever touches the soil. When your order arrives, it is important to open the box immediately. We pack our tubers in breathable materials like pine shavings to keep them healthy during transit, but they need fresh air once they reach your home.
Check your tubers for "eyes." These are small bumps or sprouts located near the neck of the tuber, similar to the eyes on a potato. A tuber must have at least one eye to grow a successful plant. If you do not see eyes right away, do not worry. Some varieties take a little longer to wake up from dormancy.
If it is still too cold to plant outside, you can store your tubers in a cool, dark, and frost-free area. A temperature between 40°F and 45°F is ideal. Keep them in their original packaging or in a box with peat moss to prevent them from drying out. If the tubers look a bit shriveled, a very light misting of water can help, but avoid making them wet, as this leads to rot.
Choosing the Right Planting Site
Success with dahlias starts with the right location. These plants are native to Mexico and Central America, so they crave warmth and sunshine. Matching the plant's needs to your garden space is the most important care step you can take.
For more help choosing a site, see where to plant a dahlia for best blooms.
Sunlight Requirements
Dahlias need plenty of fuel to produce their large, intricate blooms. They require at least 6 to 8 hours of direct sunlight every day. Morning sun is particularly beneficial as it helps dry the dew off the leaves, which reduces the risk of fungal issues. If you live in an extremely hot climate, a spot that provides a little light shade during the scorching afternoon hours can help prevent the petals from fading or wilting.
Soil and Drainage
Dahlias are not overly picky about soil type, but they must have good drainage. Drainage refers to how fast water leaves the soil after a rain or watering. Dahlias do not like "wet feet." If the soil stays soggy, the tubers are likely to rot before they ever sprout.
If you have heavy clay soil, you can improve it by adding compost or peat moss. This creates a looser structure that allows water to move through more easily. Alternatively, consider planting in raised beds. Raised beds offer excellent control over soil quality and drainage, making them a favorite choice for many dahlia enthusiasts.
Space to Breathe
Dahlias need room to grow. Good air circulation is essential for keeping the foliage healthy and preventing powdery mildew. Avoid crowding them against walls or other large plants. When you give them enough space, you allow the sun and wind to reach every part of the plant.
Planting Your Dahlias Correctly
Timing is more important than almost any other tip when it comes to planting. Dahlias are very sensitive to cold. You should wait to plant your tubers until the danger of frost has passed and the soil has warmed to at least 60°F. A good rule of thumb is to plant your dahlias at the same time you would plant tomatoes in your vegetable garden.
If you want a deeper walkthrough, when to plant dahlias is a helpful guide.
Digging the Hole
Start by digging a hole about 6 to 8 inches deep and about 8 to 12 inches wide. You want the soil to be loose so the roots can expand easily. If you wish to add a little compost or a handful of bone meal to the bottom of the hole, you can, but avoid high-nitrogen fertilizers at this stage.
Placement and Depth
Place the tuber horizontally in the hole with the "eye" or sprout facing up. If you are planting a clump of tubers, set the entire clump in the hole with the old stem pointing up. Cover the tuber with about 3 to 4 inches of soil. As the stem grows, you can gradually fill in the rest of the hole until it is level with the ground.
If you need a refresher on depth, see how deep to plant dahlia tubers.
Spacing Requirements
The amount of space between plants depends on the variety you are growing:
- Large Varieties (Dinnerplate and Decorative): Space these 18 to 24 inches apart.
- Medium Varieties: Space these 12 to 18 inches apart.
- Border or Dwarf Varieties: Space these 9 to 12 inches apart.
How close you can plant dahlias depends on the size and form of the tuber you choose.
Key Takeaway: Proper spacing and timing are the foundation of a healthy dahlia. Wait for warm soil and give each plant enough room to reach its full potential without competing for light or air.
The Golden Rule of Watering
One of the most common mistakes in dahlia care happens right after planting. It is tempting to water your tubers immediately, but you should wait.
Dahlia tubers do not have a root system yet, so they cannot absorb much water. Adding moisture to the soil at this stage often leads to rot. In most regions, there is enough natural moisture in the soil to trigger growth. You should not begin regular watering until you see the first green shoots emerging from the ground.
Once the plants are established (about 12 inches tall), they will need a consistent supply of water. Dahlias are thirsty plants, especially when they begin blooming. Water deeply 2 or 3 times a week. In hot, dry weather, you may need to water more frequently. Aim the water at the base of the plant rather than the leaves to keep the foliage dry and healthy.
Essential Maintenance: Pinching and Staking
If you want the most flowers possible, there are two maintenance tasks you cannot skip: pinching and staking. These steps transform a tall, gangly plant into a sturdy, bloom-filled bush.
Why You Should Pinch
Pinching sounds intimidating to beginners, but it is actually very simple and highly effective. When your dahlia plant is about 12 to 16 inches tall and has four sets of leaves, snip off the top of the main center stem.
This signals the plant to stop growing upward and start growing outward. It encourages lateral branching, which results in a bushier plant with more stems. More stems mean more flowers! If you don't pinch, the plant may produce one large bloom on a single tall stalk, which is much more likely to fall over in the wind.
Support for Heavy Blooms
Most dahlias grow to be 3 to 5 feet tall. Because their flowers are so large and heavy, the stems can easily snap during a summer thunderstorm or a gust of wind. Providing support is essential.
It is best to put your stakes in the ground at the time of planting. This prevents you from accidentally driving a stake through the tuber later in the season. You can use wooden stakes, bamboo poles, or even sturdy tomato cages. As the plant grows, use soft garden twine to gently tie the stems to the support every 12 inches or so.
What to do next:
- Wait until the plant is 12 inches tall.
- Locate the central stem and the top set of leaves.
- Use clean garden shears to snip off the top 2-3 inches.
- Check your stakes and ties weekly as the plant grows taller.
Feeding Your Dahlias
Dahlias are "heavy feeders," meaning they need a lot of nutrients to produce their spectacular display. However, the type of fertilizer you use matters.
In the early stages of growth, dahlias benefit from a balanced fertilizer. Once the plants start blooming, you should switch to a fertilizer that is lower in nitrogen and higher in phosphorus and potassium (such as a 5-10-10 or 10-20-20 formula). High nitrogen levels encourage lots of green leaves but can lead to weak stems and fewer flowers.
Avoid over-fertilizing. Feeding your plants once a month from mid-summer through early autumn is usually sufficient. If your soil is already very rich in organic matter, you may find that your dahlias perform beautifully with even less supplemental feeding.
Harvesting and Deadheading
The best part of taking care of a dahlia plant is the harvest. Dahlias are world-class cut flowers, and the more you cut them, the more they will bloom.
Browse best-selling dahlias back in stock for more cutting-garden favorites.
Cutting for Bouquets
For the longest vase life, cut your dahlias in the cool of the morning. Choose flowers that are almost fully open, as dahlia buds do not open much further once they are cut. Place the stems immediately into a bucket of room-temperature water. Before putting them in a vase, strip off any leaves that would be below the water line to prevent bacterial growth.
The Importance of Deadheading
If you aren't cutting flowers for bouquets, you must "deadhead" the spent blooms. Deadheading is the process of removing faded flowers. When a flower stays on the plant and starts to form seeds, the plant receives a signal that its job is done. By removing the old flowers, you trick the plant into thinking it still needs to produce seeds, so it keeps churning out new buds.
When deadheading, don't just snip off the flower head. Cut the stem back to a point where it meets a main branch or a leaf node. This keeps the plant looking tidy and encourages stronger new growth.
Protecting Your Plants
While dahlias are generally robust, they do have a few common visitors. Being proactive is the easiest way to keep your plants healthy.
Common Pests
Slugs and snails are the most frequent problem for young dahlia plants. They love the tender green shoots that emerge in late spring. You can manage them using organic slug bait or by removing them by hand in the evening.
Earwigs can sometimes nibble on the petals of open flowers. Keeping the area around your dahlias clear of debris and fallen leaves gives these pests fewer places to hide. If you notice tiny holes in the leaves, it could be aphids or spider mites. A strong blast of water from the hose is often enough to knock them off the plant.
Pet and Child Safety
It is important to note that dahlia tubers and leaves are mildly toxic to dogs, cats, and horses. If ingested, they can cause digestive upset or skin irritation. If you have curious pets or small children, it is a good idea to plant your dahlias in a fenced area or a spot where they won't be easily reached.
End of Season Care and Overwintering
Dahlias will continue to bloom beautifully until the first frost. Once a hard frost hits, the foliage will turn black and die back. This is the signal that the growing season has ended.
For zone-specific timing, check the hardiness zone map before you decide whether to lift tubers.
Understanding Your Zone
How you care for your dahlias in the winter depends on your USDA hardiness zone. Dahlias are tender perennials, meaning they can only survive the winter in the ground in warmer climates (Zones 8 and higher).
- Zones 8-11: You can usually leave your tubers in the ground. Cut the stalks back to about 3 or 4 inches and cover the area with a thick layer of mulch to protect them from excessive moisture and occasional cold snaps.
- Zones 3-7: The ground will freeze deep enough to kill the tubers. You must "lift" and store them if you want to grow the same plants next year.
Lifting and Storing Tubers
If you live in a cold climate, wait about two weeks after the first frost before digging up your tubers. This allows the tubers to "cure" and prepare for dormancy.
- Cut back the stalks: Leave about 4 to 6 inches of stem to use as a handle.
- Dig carefully: Use a garden fork to gently lift the clump of tubers from the soil. Be careful not to nick or break the "necks" of the tubers.
- Clean and dry: Gently shake off the excess soil. Let the tubers air dry in a protected, frost-free area for a day or two.
- Pack for winter: Place the tubers in a box or crate. Surround them with slightly damp peat moss, vermiculite, or wood shavings.
- Store: Keep the box in a cool (40-50°F), dark place like a basement or crawlspace. Check on them once a month to ensure they aren't rotting or drying out completely.
Conclusion
Taking care of a dahlia plant is a journey that rewards you with some of the most spectacular blooms in the floral world. By focusing on the basics—sunlight, drainage, and a little bit of patience with watering—you can transform a simple tuber into a garden masterpiece. Remember that gardening is an ongoing learning process, and every season brings a new opportunity to watch these incredible plants thrive.
At Longfield Gardens, we are here to support your gardening success with high-quality tubers and practical advice. Whether you are a first-time grower or a seasoned pro, the joy of seeing that first dahlia bud open never fades.
For ordering and shipping details, visit our shipping information page.
- Wait for warm soil before planting.
- Don't water until you see green sprouts.
- Pinch the center stem for a bushier plant.
- Deadhead regularly to keep the blooms coming.
Dahlias are a wonderful investment in your garden's beauty. With just a few minutes of care each week, they will reward you with a bounty of color that lasts until the very end of the season.
We look forward to seeing your garden grow. Happy planting!
FAQ
When is the best time to plant dahlia tubers?
The best time to plant is in late spring, once the danger of frost has passed and the soil temperature reaches about 60°F. In most regions, this is around the same time you would plant tomatoes or peppers. Planting too early in cold, wet soil can cause the tubers to rot before they have a chance to grow.
Why are my dahlias growing tall but not producing many flowers?
This is usually caused by too much nitrogen in the fertilizer or not enough sunlight. High-nitrogen fertilizers encourage leaf growth at the expense of blooms. Ensure your plants get at least 6 to 8 hours of sun and use a fertilizer higher in phosphorus and potassium once the blooming season begins.
Do I really have to pinch my dahlia plants?
While it isn't strictly required for the plant to survive, pinching is highly recommended. Snipping off the top of the main stem when the plant is about 12 inches tall encourages branching. This results in a sturdier, bushier plant that produces significantly more flowers throughout the summer and fall.
How often should I water my dahlias?
After the initial sprouts emerge, dahlias generally need deep watering 2 or 3 times a week. The goal is to keep the soil consistently moist but not waterlogged. During periods of extreme heat or in sandy soils, you may need to water more frequently. Always check the top inch of soil; if it feels dry, it is time to water.
For help with winter survival, see whether you should dig up dahlia bulbs every year.
For more inspiration, browse our dahlia collections and new dahlias.
For special pricing, see 20% off dinnerplate dahlias, 30% off select dinnerplate dahlias, or BOGO select dahlias.
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