Table of Contents
- Introduction
- The Magic of Dinner Plate Dahlias
- Selecting the Perfect Site
- When to Plant Your Tubers
- Preparing Your Soil for Success
- Step-by-Step Planting Instructions
- The Importance of Proper Spacing
- Staking and Support Strategies
- Watering and Feeding for Maximum Growth
- Techniques for Achieving the Largest Blooms
- Popular Varieties to Grow
- Caring for Your Dahlias Through the Season
- Conclusion
- FAQ
Introduction
There is nothing quite like the excitement of seeing your first dinner plate dahlias bloom. These spectacular flowers are the true heavyweights of the summer garden, producing blossoms that can measure 8 to 12 inches across. When you see a "Cafe au Lait" or "Emory Paul" dahlia in full bloom, it is easy to see why they have become a favorite for home gardeners and floral designers alike. At Longfield Gardens, we want to help you experience that "wow" factor in your own backyard by providing high-quality tubers and the practical knowledge you need to succeed.
Growing these giants is a rewarding process that any gardener can master with a few simple steps. This guide will walk you through the essential techniques for planting dinner plate dahlia tubers, from choosing the right spot to providing the sturdy support these large plants require. Whether you are a beginner or looking to improve your harvest, we have gathered the most effective tips to ensure your season is filled with color. With the right timing and a little bit of patience, you can turn your garden into a show-stopping floral display.
The Magic of Dinner Plate Dahlias
The term "dinner plate" is not a formal botanical classification, but rather a descriptive name for any dahlia variety that produces exceptionally large flowers. To earn this title, a bloom typically needs to reach at least 8 inches in diameter, though some varieties can grow even larger. These plants are "flower machines," starting their show in midsummer and continuing to bloom until the first frost of autumn.
Dinner plate dahlias come in a staggering array of shapes and colors. You might see the classic, perfectly cupped petals of a formal decorative type, or the wild, shaggy petals of a "cactus" or "laciniated" variety. Because the plants themselves can grow 4 to 6 feet tall, they function more like flowering shrubs in the landscape. They provide excellent height for the back of a flower border and serve as the undisputed stars of summer bouquets.
While their size might make them look intimidating, dinner plate dahlias are quite accessible. They grow from tubers, which are thickened underground roots that store energy for the plant. If you provide these tubers with the right environment, they will reward you with months of beauty and a new crop of tubers to dig up and save for the following year.
Selecting the Perfect Site
Success begins with "right plant, right place." Because dinner plate dahlias put so much energy into producing giant blooms and tall stems, they have specific needs when it comes to their environment.
Sunlight Requirements
Dahlias are sun worshippers. For the strongest stems and the most flowers, your planting site should receive 6 to 8 hours of direct sunlight every day. Morning sun is particularly beneficial because it helps dry the overnight dew off the foliage, which keeps the plants healthy. If your garden is in a very hot climate, a little bit of afternoon shade can prevent the blooms from fading too quickly, but full sun is generally the best choice for most U.S. gardeners.
Soil and Drainage
"Drainage" is a word gardeners use to describe how fast water leaves the soil. This is the most important factor in site selection. Dahlia tubers are prone to rot if they sit in cold, soggy ground. You want soil that is loose, crumbly, and rich in organic matter. If you have heavy clay soil that stays wet after a rain, consider planting your dahlias in raised beds. This keeps the tubers elevated and ensures excess water can drain away easily.
Wind Protection
Because dinner plate dahlias grow so tall and have heavy flower heads, they can be vulnerable to wind. A summer thunderstorm with strong gusts can easily snap a stem or tip over an unsupported plant. Try to pick a spot that has some natural protection, such as near a fence, a hedge, or the side of a building. Just make sure the spot still gets plenty of sun and has good airflow to prevent mildew.
Key Takeaway: Choose a sunny, well-drained spot with some protection from strong winds to give your giant dahlias the best start.
When to Plant Your Tubers
One of the most common mistakes in gardening is planting too early. While it is tempting to get your tubers in the ground as soon as the snow melts, dahlias are tropical plants that love warmth. They are native to Mexico and have no tolerance for frost or cold soil.
Monitor Soil Temperature
You should wait to plant your dinner plate dahlia tubers until the soil temperature reaches at least 60°F. A simple way to judge this is to wait until you are ready to plant your tomatoes and peppers. If the weather is still cool and wet, it is better to wait. Planting in cold, damp soil increases the risk of the tuber rotting before it has a chance to grow.
Understand Your Zone
Our USDA hardiness zone map helps with this timing. We ship tubers based on your USDA hardiness zone so they arrive around the time it is safe to plant in your area. However, local weather varies every year. Always check your local frost dates and ensure the danger of a late spring freeze has passed before you move your tubers outdoors.
Starting Early Indoors
If you live in a northern climate with a short growing season, you can give your dinner plate dahlias a head start. About four to six weeks before the last frost, plant your tubers in large pots filled with damp potting soil. Keep them in a warm, sunny spot indoors or in a greenhouse. By the time the soil outside is warm enough, you will have a small plant ready to go, which can lead to earlier blooms in July rather than August.
Preparing Your Soil for Success
Think of dinner plate dahlias as the "beefsteak tomatoes" of the flower world. They are heavy feeders that require plenty of nutrients to reach their full potential. Preparing the soil before you plant is much easier than trying to fix it later in the season.
Adding Organic Matter
Before planting, mix several inches of compost, aged manure, or leaf mold into the soil. This improves the soil structure and provides a slow-release source of nutrients. Organic matter helps sandy soil hold onto moisture and helps break up heavy clay soil for better drainage.
Checking Soil pH
Dahlias prefer a soil pH that is slightly acidic to neutral, generally between 6.0 and 7.0. If you are unsure about your soil, a simple test from a local extension service can give you exact numbers. If your soil is too acidic, you can add a bit of garden lime; if it is too alkaline, sulfur or peat moss can help bring it back into balance.
Avoid High-Nitrogen Fertilizers at Planting
While it is okay to mix in some compost, avoid using high-nitrogen fertilizers directly in the planting hole. Too much nitrogen early on can encourage lush green leaves but very few flowers. It can also make the tubers more susceptible to rot. A balanced, all-purpose fertilizer or a bit of bone meal mixed into the bottom of the hole is usually sufficient for the early stages of growth. For a step-by-step refresher, see How to Plant Dahlia Bulbs for a Stunning Garden.
Step-by-Step Planting Instructions
Once the soil is warm and your site is ready, it is time to plant. Handling the tubers with care is important, as the "neck" of the tuber is fragile.
- Dig the hole: For each tuber, dig a hole about 6 to 8 inches deep. If you are planting in a row, make sure the holes are spaced correctly (see the spacing section below). For more detail on planting depth, see How Deep Should Dahlia Bulbs Be Planted?.
- Add support first: This is a professional tip that saves a lot of trouble. Drive your stake into the ground before you put the tuber in the hole. This prevents you from accidentally driving a stake through the tuber later.
- Position the tuber: Lay the tuber horizontally in the bottom of the hole. Look for the "eye," which is a small bump or sprout near the neck where the tuber was attached to the old stem. If you see the eye, point it upward. If you don't see an eye yet, don't worry—just lay it flat.
- Cover with soil: Fill the hole with about 2 to 3 inches of soil. Do not fill the hole all the way to the top yet if you are in a very hot climate, as this allows the sun to warm the tuber more quickly. As the sprout grows, you can gradually fill in the rest of the soil until it is level with the ground.
- Don't water yet: This is the most important rule of dahlia planting. Unless your soil is bone-dry, do not water the tubers immediately after planting. The tuber has enough stored energy and moisture to start growing. Watering too early can lead to rot. Wait until you see the first green shoots poking through the soil before you start a regular watering routine.
What to do next:
- Check your tubers for "eyes" before planting.
- Drive your stakes into the ground first to protect the tubers.
- Resist the urge to water until you see green growth.
The Importance of Proper Spacing
Because dinner plate dahlias grow into massive plants, they need plenty of "elbow room." It is tempting to crowd them together to get a fuller look, but this often leads to problems later in the season.
Space for Airflow
Proper spacing is essential for preventing diseases like powdery mildew. When plants are too close together, air cannot move between the leaves, creating a humid environment that fungi love. For dinner plate varieties, we recommend spacing the tubers 18 to 24 inches apart.
Space for Growth
Remember that these plants will likely grow 4 to 5 feet tall and 2 to 3 feet wide. Giving them enough space ensures that each plant gets its fair share of sunlight and nutrients from the soil. If you are planting in a dedicated cutting garden, leave at least 3 feet between your rows so you have a path to walk through when it is time to harvest your blooms.
Container Spacing
If you are growing dinner plate dahlias in pots, use a large container. A 5-gallon bucket or a pot that is at least 12 to 15 inches in diameter is the minimum size for one dinner plate tuber. Growing in containers is a great option for decks or patios, but these plants will need more frequent watering and fertilizing than those in the ground. For more container guidance, see Can You Grow Dinner Plate Dahlias in Pots?.
Staking and Support Strategies
You cannot grow dinner plate dahlias successfully without support. The sheer weight of an 11-inch "American Dream" bloom, especially after a rain shower, is enough to pull an entire plant to the ground.
Wooden or Metal Stakes
Sturdy 5- to 6-foot wooden or metal garden stakes are the most common choice. As the plant grows, use soft garden twine or strips of old fabric to tie the main stem to the stake every 12 inches. Be careful not to tie the twine too tightly; you want to support the stem, not strangle it.
Tomato Cages
For a lower-maintenance approach, you can use heavy-duty tomato cages. Place the cage over the tuber at planting time. As the dahlia grows, the branches will grow through the wires of the cage, which provides support from all sides. This is a great option if you don't want to spend time tying up stems every week. For a simple walkthrough, see How to Pinch and Stake Dahlias.
The "Corral" Method
If you are growing a long row of dahlias, you can use the corral method. Drive sturdy posts into the ground at the four corners of your bed and every 5 to 10 feet along the sides. Run several levels of strong twine around the perimeter of the posts, creating a "fence" that keeps the plants from falling outward. You can also run twine across the middle of the bed in a grid pattern for extra stability.
Watering and Feeding for Maximum Growth
Once your dinner plate dahlias have sprouted and are about 6 to 12 inches tall, their needs change. They transition from dormant tubers to fast-growing plants that need consistent moisture and fuel.
Deep Watering
Dahlias prefer deep, infrequent watering over light daily sprinkles. Aim for about one inch of water per week, either from rain or irrigation. When you water, target the base of the plant and try to keep the foliage dry. This helps prevent leaf diseases and discourages pests like slugs. In the heat of midsummer, you may need to water two or three times a week to keep the soil consistently moist.
Fertilizing Routine
We recommend starting a regular fertilizing schedule once the plants are about a foot tall. Use a fertilizer that is low in nitrogen and high in phosphorus and potassium (such as a 5-10-10 or 10-20-20 formula). Phosphorus is the key ingredient for big, beautiful blooms. Fertilize about once a month until early autumn. Avoid over-fertilizing, as this can lead to weak stems and tubers that don't store well over the winter.
Mulching
Once the weather is consistently hot, a layer of mulch can help the soil retain moisture. Use organic materials like shredded bark, straw, or compost. Keep the mulch a few inches away from the main stem to prevent rot. Mulching also helps suppress weeds that would otherwise compete with your dahlias for nutrients.
Techniques for Achieving the Largest Blooms
If your goal is to grow flowers that truly look like dinner plates, there are two professional techniques you should use: pinching and disbudding.
Pinching for a Bushier Plant
When your dahlia plant is about 12 to 16 inches tall and has three or four sets of leaves, "pinch" off the top of the main center stem. You can use sharp scissors or your thumb and forefinger. This might feel like you are hurting the plant, but it actually encourages it to branch out from the base. Instead of one tall, lanky stem, you will get a bushier plant with more stems and, ultimately, more flowers.
Disbudding for Giant Blooms
This is the "secret" to getting those massive 10-inch flowers. On a dahlia stem, you will usually see a cluster of three buds: one large central bud and two smaller side buds. If you leave all three, you will get three medium-sized flowers. If you remove the two smaller side buds when they are about the size of a pea, the plant will put all its energy into that one central bloom, making it significantly larger and more impressive.
Deadheading
To keep the plant producing flowers all season long, you must remove "spent" blooms—those that have started to fade. This is called deadheading. When a flower begins to lose its petals or the back of the flower feels soft, cut the stem back to a point just above a set of leaves. This prevents the plant from putting energy into seed production and signals it to keep making new buds.
Popular Varieties to Grow
At Longfield Gardens, we offer a wide selection of Dinnerplate Dahlias that have been trialed for performance and beauty. Here are a few varieties that are consistently popular with our customers:
- Cafe au Lait: This is perhaps the most famous dinner plate dahlia in the world. Its blooms are a stunning blend of creamy peach, blush pink, and ivory. It is a favorite for weddings and has a classic, elegant look.
- Thomas Edison: For a bold splash of color, you can't beat this deep, royal purple variety. It is a vigorous grower and produces exceptionally sturdy stems.
- Emory Paul: If you want the biggest flowers possible, this is the one. Its shaggy, rosy-pink blooms can easily reach 12 inches in diameter.
- Kelvin Floodlight: This award-winning variety produces enormous, bright yellow flowers that light up the garden. It is a reliable performer and a great choice for beginners.
- Tartan: A striking bicolor variety with wavy petals of deep burgundy and crisp white. It adds a dramatic, sophisticated touch to any bouquet.
When choosing varieties, consider how they will look together in the garden and in a vase. Mixing different colors and petal shapes creates a dynamic and interesting display that will last from summer into late fall.
Caring for Your Dahlias Through the Season
As the season progresses, a little bit of maintenance goes a long way in keeping your dinner plate dahlias healthy and productive.
Managing Pests
Keep an eye out for common garden pests like slugs, snails, and earwigs, especially when the plants are young. These pests love the tender new growth. Later in the season, you might see aphids or Japanese beetles. In most cases, a strong blast of water from the hose or an application of insecticidal soap is enough to keep them under control.
Foliar Health
In late summer, when the humidity is high, dahlias can sometimes develop powdery mildew, which looks like a white dusting on the leaves. As we mentioned, good spacing is the best prevention. If you see it starting, you can use a neem oil spray or a mixture of baking soda and water to slow its spread. Always remove any yellowing or diseased leaves from the bottom of the plant to improve airflow.
Harvesting for Bouquets
One of the best things about dahlias is that the more you cut them, the more they bloom. When cutting dinner plate dahlias for a vase, do so in the cool of the morning. Choose flowers that are almost fully open, as dahlias do not open much after they are cut. Use a sharp, clean knife or shears and place the stems immediately into a bucket of water. For the longest vase life, change the water daily and keep the flowers away from direct sunlight and heat.
Season Maintenance Tips:
- Cut flowers regularly to encourage new buds.
- Keep an eye out for slugs and earwigs on new growth.
- Remove faded blooms immediately to keep the plant tidy.
Conclusion
Planting dinner plate dahlia tubers is one of the most rewarding projects a home gardener can undertake. By focusing on the basics—choosing a sunny spot, waiting for warm soil, and providing sturdy support—you can grow spectacular flowers that will be the envy of the neighborhood. At Longfield Gardens, we take pride in helping you bring these garden giants to life. Remember that gardening is a journey, and every season brings new opportunities to learn and grow. We stand behind the quality of our tubers and are here to support you as you create a more beautiful yard.
"The secret to giant dahlias isn't a miracle product; it is simply getting the timing right and giving the plant the space and support it needs to thrive."
Now that you know how to plant and care for these magnificent flowers, the next step is to choose your favorite colors and get ready for a summer of breathtaking blooms. We invite you to explore our Dinnerplate Dahlias and start planning your most beautiful garden yet.
FAQ
How deep should I plant my dinner plate dahlia tubers?
You should plant the tubers about 4 to 6 inches deep in a hole that is 6 to 8 inches deep. Lay the tuber horizontally at the bottom of the hole. If you see a small sprout or "eye," point it toward the sky, but if not, laying it flat will work perfectly well as the plant will naturally find its way to the surface. For a fuller walkthrough, see How Deep Should Dahlia Bulbs Be Planted?.
Do I need to water my dahlia tubers right after planting?
No, you should avoid watering your tubers immediately after planting unless the soil is exceptionally dry. The tuber contains enough moisture to begin its growth process. Watering too early, especially in cool spring soil, is a common cause of tuber rot. Wait until you see the first green shoots appearing above the soil before starting a regular watering routine.
Why is my dinner plate dahlia not producing giant flowers?
The most common reasons for smaller flowers are a lack of sunlight, too much nitrogen fertilizer, or failing to "disbud." Ensure your plant gets at least 6 to 8 hours of sun and use a fertilizer high in phosphorus. To get the largest possible blooms, remove the two smaller side buds in each cluster, allowing the plant to focus all its energy on the single central flower.
Can I grow dinner plate dahlias in containers?
Yes, you can grow these large dahlias in containers, provided the pots are big enough. Use a container that holds at least 5 gallons of soil (about 12 to 15 inches in diameter). Keep in mind that container-grown dahlias dry out faster than those in the ground and will require more frequent watering and a consistent fertilizing schedule to produce those signature large blooms. For more tips, see Can You Grow Dinner Plate Dahlias in Pots?.