How Tall Do Dahlias Grow? A Guide to Dahlia Plant Heights

Dahlias are cherished for their showy, colorful blooms that energize gardens from midsummer through fall. But did you know there’s great variety when it comes to dahlia plant heights? Some cute little border dahlias max out around 1 foot tall, while giant dinnerplate types can tower over your head at 6 feet or more!

So if you’re wondering, “How tall do dahlias get?” the answer is It depends! Read on to learn about the factors that determine dahlia height, plus tips for selecting the perfect size dahlia for your space.

What Determines Dahlia Plant Height?

Several key factors impact how tall a dahlia will grow

Dahlia Type

There are over 20 types of dahlias, and some naturally grow much taller than others. Large-flowered cactus, semi-cactus and dinnerplate dahlias often reach 4-6 feet. Meanwhile, charming border dahlias max out around 1-2 feet tall.

Genetics

Even within the same dahlia type, genetics play a role. For example, the “Bishop of Llandaff” dinnerplate dahlia grows 3-4 feet tall. But the cultivar “Cafe au Lait” typically only reaches 2-3 feet, despite both being dinnerplate types.

Growing Conditions

The amount of sun, soil quality, water and fertilizer impacts size. Dahlias grown in rich soil with plenty of TLC can achieve maximum height. Those in poor, dry soil may stay much more compact.

Pruning and Disbudding

Pruning and disbudding (removing side buds to get fewer, larger blooms) keeps plants shorter and more compact compared to leaving them unpruned.

Dahlia Height Categories

To make it easier to select the right size for your space, dahlias are often grouped into height categories:

Dwarf dahlias – under 2 feet tall
Border or bedding dahlias – 2-3 feet tall
Medium dahlias – 3-4 feet tall

Tall dahlias – over 4 feet tall

Here’s an overview of average sizes for different dahlia types:

Dwarf Dahlias

Pompon: Up to 24 inches tall
Single: Up to 24 inches tall
Ball: 12-18 inches tall

Miniature Ball: 12-18 inches tall

Dwarf varieties are ideal for containers, edging beds, and small spaces.

Border/Bedding Dahlias

Border: 15-24 inches tall

Small Decorative: Up to 36 inches tall
Small Cactus: Up to 36 inches tall
Waterlily: 24-36 inches tall

These compact dahlias are perfect for beds, borders, and mid-sized containers. Popular series include Gallery and Melody.

Medium Dahlias

Large Decorative: 36-48 inches tall
Large Cactus: 36-48 inches tall

Semi-Cactus: 36-48 inches tall

Medium dahlias add bold color to beds and mixed borders. They may need light staking.

Tall Dahlias

Giant/Novelty: Over 48 inches tall

Dinnerplate: Over 48 inches tall

Massive dinnerplate blooms atop 6 foot stems make an unforgettable statement. Require staking.

Selecting Dahlias by Height

Here are tips for choosing dahlias based on their mature height:

For Containers

Opt for dwarf pompon, ball and mini varieties under 24 inches tall. Border dahlias up to 36 inches work for larger pots.

For Edging Beds and Walkways

Dwarf to border dahlias from 15-24 inches tall add charm along edges but won’t overwhelm pathways.

For Mixed Borders and Beds

Choose border or medium dahlias in the 24-48 inch range to blend with other mid-sized perennials,annuals and roses.

For Cutting Gardens

Tall dahlias over 4 feet have the longest stems for cutting. Plant en masse for an abundant harvest.

For Small Spaces

Compact border or dwarf dahlias under 2-3 feet are ideal for tiny yards, courtyards, and urban balconies.

For Grand Displays

Giant dinnerplate and novelty dahlias make jaw-dropping focal points in large gardens. Be sure to stake them!

Tips for Managing Dahlia Height

If a variety starts growing taller than expected, you can take steps to keep it in check:

Pinch out the central stem to promote bushier growth
Remove lower buds and leaves to hide “leggy” stems

Stake tall plants to support top-heavy blooms
Disbud regularly to get fewer, larger flowers
Cut back extra-tall stems partway to reduce height

Proper pinching and disbudding will help restrain the length of even very tall dahlias. For smaller border dahlias, little intervention is needed to maintain a compact shape.

Discover the Right Dahlias for Your Garden

One of the joys of dahlia gardening is selecting from the incredibly diverse range of flower types, colors, and plant habits. By understanding the factors that determine dahlia height, you’ll be able to confidently choose varieties that will thrive at the scale you need – whether it’s petite pompons for pots, medium border types for beds, or towering dinnerplate blooms to anchor a landscape.

Let your space, style and purpose guide you as you explore the vibrant world of dahlias. With so many sizes to suit any garden, you’re sure to find your perfect plant partners!

Planting, Growing, and Caring for Dahlias

Dahlias are breathtakingly gorgeous flowers that come in every color of the rainbow. The tubers are planted in late spring. Learn more about planting, growing, and caring for dazzling dahlia flowers.

It’s like going through a button box to choose your favorite dahlia. The flowers come in all shapes and sizes, from tiny 2-inch pompoms that look like lollipops to huge 15-inch “dinner plates.” ” Most varieties grow 4 to 5 feet tall. Dahlias can be white, yellow, orange, pink, dark pink, red, dark red, lavender, purple, black, light blend, bronze, flame, dark blend, variegated, or bicolor.

Dahlia is a genus of tuberous plants that are members of the Asteraceae family. Plant the tubers in the ground in late spring, around May. They usually flower from July until the first frost in the fall. Dahlias are perfect for a border garden and make lovely cut flowers. Growing vegetables? Put a row of dahlias on the border, where they will not shade your edibles.

Are Dahlias Perennials or Annuals?

Dahlias are tender perennials in their native warm climate of Mexico. In the U. S. , they are considered perennials in hardiness zones 8 and higher. See the USDA hardiness zone page.

However, in colder regions (zones 7 and lower), dahlias are treated as annuals. That said, some gardeners have had luck keeping the dahlias in the ground in zones 6 and 7.

If you live in a cold area, you can also just dig up the tubers after the first frost and keep them in your garage until spring. Learn how to dig up dahlias in the guide below. Read Next.

Dahlias do best with 6 to 8 hours of direct sunlight, preferably in the morning. They also do better when they are out of the wind. Consider their size at maturity when planting. They grow best in rich, well-draining soil with a pH of 6. 0 to 7. 5. Old manure or compost can be added to heavy clay soil to make it lighter and more porous so that water can drain better.

How to Grow Dahlias – From Tubers to Gorgeous Blooms – A Complete Guide // Northlawn Flower Farm

FAQ

Do dahlias like full sun or shade?

Dahlias love to be in a sunny location— an area that receives at least 6-8 hours of direct sunlight is preferred. Dahlias will also grow in shady areas but generally will be taller and require more staking and care. Dahlias love to be in the dirt. The dirt is a friend to Dahlia Tubers.

Do dahlias need a lot of room?

How much space do dahlias need? Here’s the short answer: dahlias require 1 to 1.75 square feet per plant. If you’re used to thinking in planting distances, that means planting each tuber 12 to 16 inches apart. A row 20′ long x 4′ wide (80 square feet) can grow up to 80 plants.

How many times a year do dahlias bloom?

Dahlias, grown for their beautiful flowers, come in all colors except the elusive blue. They bloom nonstop from summer until frost in a variety of shapes and sizes.

Do dahlias grow better in pots or the ground?

Dahlias grow well in pots, though you need to be very careful not to let them repeatedly dry out. 1 They also will need to be regularly fertilized during the growing season, and many will need to be staked so they don’t fall over.