Learn How to Grow and Care for Dinner Plate Dahlia Like a Pro

When you want show-stopping plants with big flowers, nothing beats dinner plate dahlias. These tall, colorful, long-blooming plants feature flowerheads that can grow to more than 12 inches wide.

The term dinner plate dahlias is used for varieties and cultivars with especially large blooms—that's any dahlia with flowers reaching 8 inches in width or more.

These tender perennials generally put on a show from midsummer until the first fall frosts, but they aren't the most low-maintenance plants. Pick a sunny spot with rich, well-drained soil and water and fertilize frequently to see them thrive.

You'll also want to regularly stake, disbud, and deadhead to enable the blooms to reach their best potential. Factor in digging up and dividing your dahlias to store their tuberous roots overwinter in cold countries if you aren’t treating the plants as annuals.

Keep dinner plate dahlias away from curious pets that like to nibble because this plant is toxic to dogs and cats.

Dinner Plate Dahlia Care

Dinner plate dahlias can be grown as perennials where the climate is mild year-round, or you can appreciate them as annuals. Here are the main care requirements for dinner plate dahlias:

• Plant tubers in the spring after the last frosts.
• Position in full sunlight.
• Plant in a rich, well-drained soil.
• Water the plants weekly to twice weekly during the growing season (depending on how dry conditions are).
• Stake these tall plants to prevent drooping and breaking stalks.
• Disbud to leave one bud per flower cluster.
• Deadhead spent blooms.
• Dig up and store the tubers (enlarged roots) overwinter in cold regions.

Light

Dinner plate dahlias are sun worshippers. Plant them in a full sun position where they get at least six to eight hours of direct sun daily.

They will survive in partial shade, but the blooms won’t be so impressive, and the plants can look leggy.

Soil

Pick a rich, loamy, well-draining soil for best blooming and amend generously with organic matter, such as manure, pine bark, or decomposed leaves.

This helps achieve the loose, crumbly, aerated conditions that dinner plate dahlias need to promote a healthy root system.

Always loosen dense, clay soils before planting tubers, and add some sand or peat moss to help promote better drainage.

If you have acidic soil, adding a cup of lime can restore the pH to the neutral levels the plants prefer.

Water

Established dinner plate dahlias are thirsty plants that need ample water during their growing season.

Aim to keep the soil moist but not soggy. If there isn't lots of rainfall, water deeply two or three times a week—sometimes more during very hot, dry spells. Mulching helps the plants conserve water.

However, don't water tubers immediately on planting as this can lead to rotting. Wait until you see them sprouting green growth.

Temperature and Humidity

Dinner plate dahlias aren't fans of extreme temperatures or sudden fluctuations and are cold-sensitive. They do best in temperatures ranging from around 60 to 80 degrees Fahrenheit.

Always wait until spring soil temperatures reach 60 degrees Fahrenheit before planting tubers. High humidity can result in heat stress and a poor bloom season.

Fertilizer

Dinner plate dahlias can produce big, healthy blooms without fertilizer if they are in a rich soil with plenty of organic matter added.

However, these heavy feeders generally appreciate monthly fertilization during their growing season to help encourage the most impressive flowering. 

A water-soluble or low-nitrogen fertilizer with a balance of 5-10-10 or 10-10-20 usually works well.

Many dahlia enthusiasts start the season with a slightly higher nitrogen content formula to promote a strong stem before swapping to a lower nitrogen and higher phosphorus content at the end of the season to focus on those big blooms.

Types of Dinner Plate Dahlias

You're spoilt for choice when it comes to dinner plate dahlia cultivars. Sometimes they will be named by color in big box garden centers, but selecting named varieties helps ensure you provide the kind of care they need.

Some popular dinner plate dahlia types include:

• 'American Dream': The pink double flowers feature striking raspberry stripes and can be up to 11 inches wide.
• 'Cafe au lait': This award-winner features creamy peach petals on long-blooming double flowers that can reach 10 inches wide. 
• 'Emory Paul': This whopper features rosy-purple, wavy-petalled double blooms that can reach up to 14 inches wide.
• ‘Happet Blue Eyes’: These bicolor, double flowers reach 8 inches wide and have eye-catching white blooms with lilac tips. It’s also known for having solid stems.
• 'Tartan': Sure to catch the eye with blooms that are a mix of white and deep burgundy, these double flowers reach 8 inches wide.

Pruning

To maximize the bloom size on your dinner plate dahlias, always remove the two small buds next to the central one in flower clusters on the stem when they are around the size of a pea.

Each plant won't produce as many flowerheads, but the ones that do will be more impressive and well-formed.

If you like bushy, leafy specimens, pinch off a few inches of the central stem once the dahlias are at least a foot high.

And don't forget to stake these tall plants to prevent drooping or snapping stalks. Pick a stake that's at least 6 feet tall.

Tie the lower part of the stem first, once they are around a foot tall, and, as it gets taller, usually monthly, stake higher up, focusing on securing any heavy bloom-bearing branches. A less high-maintenance approach is to invest in a supportive tomato cage.

Overwintering

If you don't want to treat your plants as annuals in colder regions (below USDA hardiness zone 7), overwintering dahlias is the most time-consuming part of their care.

To see these tender perennials bloom again next season rather than suffering from root rot, the key is to dig up the tubers after the first hard frost and store them before planting out again in spring after the danger of frost has passed. Follow the steps below:

1. Before digging up the tubers, cut the stems to around six inches from the ground when the plants blacken after the first hard fall frost. The tubers should produce more eyes to create new plants by doing this. 
2. Cover the hollow cut stems with aluminum foil to stop root rot from occurring if it is rainy.
3. After around a week, the eyes should be big enough to allow you to dig up the tubers carefully.
4. Wash and cut the tuberous root clumps into sections using a sharp, sterile knife. Each section must have at least one eye (a point where the tuber joins a stalk on the previous season's growth). Trim off any rotten parts. Neglecting to divide the tuber means too many stems will appear the following season, and your plants will be less vigorous.
5. Turn the sections upside down to remove any remaining moisture and leave them for a few days to cure. 
6. Put them in a cardboard container and cover with wood chips or lightly moistened peat moss. 
7. Store them in a cool spot where temperatures remain between 32 and 50 degrees Fahrenheit. If they get too hot, the tubers will start sprouting too early.
8. In the spring, once the danger of frost has passed and your soil is at least 60 degrees Fahrenheit, you can replant the tubers. 
9. Space the tubers around 3 to 4 feet apart in holes around 5 inches deep with the eyes facing upwards.

Common Pests & Plant Diseases

To prevent the beautiful blooms of your dinner plate dahlias from being rapidly wiped out. Some pests and diseases to be vigilant for include:

• Leafhoppers: They can cause an infectious disease called asters yellow that impacts bloom growth.
• Bacterial stem rot: Look out for blackened, softening stems emitting a foul odor. Always discard infected plants immediately to prevent spread.
• Powdery mildew: You can treat this dry, white fungal foliage growth with a fungicide to control it.
• Verticillium wilt: This fungal disease can lead to wilting and death. Help prevent it by making sure your soil is well-draining.

How to Get Dinner Plate Dahlias to Bloom

Learn more about the big blooms on dinner plate dahlias to make the most of them.

Bloom Months

Bloom times vary depending on the dinner plate dahlia cultivar and planting time, but they typically start flowering around mid-July to early August.

You can appreciate the blooms for as long as eight to 10 weeks during the summer if you provide the right care and conditions.

What Do Dinner Plate Dahlia Flowers Look and Smell Like?

The appearance of dinner plate dahlias varies depending on the variety you select. Blooms can be single or double, and the shape of the petals ranges from flat to spiral to elongated cups.

They come in a wide range of colors, including white, yellow, orange, pink, red, purple, and even black.

It's all about the big blooms appearance with these flowers, as dinner plate dahlias are more commonly fragrance-free.

How to Encourage More Big Blooms

Alongside providing enough sun, water, and fertilizer, deadheading spent flowers on your dinner plate dahlias are another way to extend the bloom season.

And, as mentioned, debudding all but the central bud in a flower cluster promotes the biggest, most impressive blooms.