Dahlias are absolutely stunning flowers that come in a rainbow of colors and range dramatically in size and form. But what exactly does a dahlia plant look like as it grows and blooms through the seasons? This complete visual guide will walk you through the dahlia’s life cycle so you know exactly what to expect if you plant these gorgeous flowers in your own garden.
Dahlia Tubers
A dahlia plant starts its life as a tuber, which is a swollen underground stem that stores nutrients and energy for the plant. Dahlia tubers look a bit like small sweet potatoes. They are typically between 2 to 6 inches long and 1 to 2 inches wide. The tubers are brown or tan in color with noticeable “eyes” or growth buds from which the stems and leaves emerge. The eyes appear as small pinkish bumps on the crown of the tuber.
When selecting dahlia tubers to plant, look for ones that are firm and free of mold, wrinkles, or soft spots. Avoid any that appear damaged or rotten. The tubers can be purchased individually or in clumps still attached to a portion of the previous year’s stem. Both tuber types will grow equally well as long as they have eyes.
Emerging Shoots
Once planted in the garden, dahlia tubers send up new shoots within 1-3 weeks. Initially a single green stem pokes up through the soil’s surface and grows rapidly, reaching 6 inches within a few days. Soon the first set of divided leaves unfurls at the top of the stem in a clasp shape. More stems emerge from the eyes on the tuber and branch out as the plant establishes itself.
The emerging dahlia shoots are green and smooth. They look almost like asparagus spears poking up from the ground. The stems are hollow and succulent at first but gradually thicken and strengthen as they grow taller. Expect your dahlia sprouts to reach 12-18 inches high within the first 4-6 weeks after planting.
Leaves and Foliage
One of the great things about dahlias is the wide variety of leaf shapes and colors different cultivars display. The most common dahlia foliage is green, but hues can range from dark burgundy through various shades of purple, red, and bronze. The lacy, divided leaves have pointy oval-shaped leaflets arranged in opposite pairs along the length of the stem. Leaf shapes vary as well, with options like spiky, fern-like, rounded, and oak-leaf styles.
In most cases, the leaves are darkest when they first emerge, then lighten as they mature. Variegated varieties have leaves edged or speckled in white or yellow. As dahlias grow, the leaves get progressively smaller and may be just an inch or two long at the top of 4-6 foot tall plants. Expect each established plant to have 40 or more leaves by midsummer.
Flower Buds
About 6-8 weeks after planting dahlia tubers, the plants will start forming their first flower buds. The buds appear at the ends of the multiple branching stems They are round or oblong in shape and closed tightly at first
Some dahlia varieties produce lots of smaller buds less than an inch wide. Giant dinnerplate dahlias have huge flower buds up to 4-5 inches across! Buds are typically green or purple at first, then lighten to a yellowish-green as they mature. It takes 7-10 days for the buds to swell to full size and finally open into glorious blooms.
Flowers
When it comes to the actual dahlia blooms, the possibilities are endless! Flowers come in every color except true blue and range in size from 2 inch diameter pompoms to massive 15 inch dinner plates
There are 18 official dahlia flower forms, but some of the most popular types include:
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Cactus dahlias have long, pointed, slightly curved petals that create a spiky, starburst effect. These blooms range from 2-8 inches across
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Decorative dahlias have broad petals that curve gently back from the center. Blooms are 4-12 inches wide.
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Ball dahlias produce round, densely packed, button-like flowers about 2-6 inches across.
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Pompon dahlias have small, ball-shaped flowers with tightly clustered petals. They are usually under 3 inches wide.
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Anemone dahlias have a dense central disc surrounded by one or more outer rows of petals for a unique look. Blooms range from 3-6 inches wide.
The number of petals varies both between dahlia types and individual cultivars. You’ll find flowers with just a few dozen petals or varieties boasting hundreds of long, thin, tightly packed petals when fully open.
Expect each established dahlia plant to produce 20 or more blooms at a time, with flowers lasting up to a week in vases or on the plant before browning and fading. Deadheading spent blooms encourages more flower production.
Height and Form
Dahlias vary as much in terms of mature size and shape as they do in bloom characteristics. Plant heights range from petite 6-12 inches up to towering 8 foot nonstop beauties.
Most commonly, you’ll find dahlias reach 3-6 feet tall at maturity. Dwarf bedding dahlias and patio/balcony container types max out at around 18-24 inches tall. Giant dahlias soar to 6-8 feet high!
The overall plant shape is loosely pyramidal or vase-shaped in singles but becomes bushy and dense when multiple tubers are planted together in rows or clumps. Be sure to stake and tie tall varieties to prevent toppling in wind and heavy rains.
Changing Color
One of the remarkable things about dahlias is how their bloom colors change as the flowers age. Many varieties display different hues between the time they open and when they eventually fade. For example, you may have a red dahlia that starts off a bright crimson and mellows to a deeper burgundy-red. Other varieties might show yellow throats when newly opened that gradually expand to become a larger percentage of the petal as the bloom matures. This intriguing color-shift gives each flower added depth and visual interest.
Peak Bloom Season
Depending on your climate and the variety grown, expect dahlia flowers to reach peak bloom about 8-12 weeks after tubers are planted in late spring. Most dahlias start blooming in July and flower abundantly from August through the first frost in autumn. During peak flowering, each plant will have multiple flowers open at once, creating a spectacular display of color. Dahlias really hit their stride in September when many other garden plants are winding down. Their breathtaking blooms keep gardens vibrant into the fall season.
Post-Frost Decline
Dahlias are tender perennials that thrive in summer and fall but cannot tolerate freezing temperatures. When the first light frost hits in autumn, the foliage quickly turns dark brown or black and the blooms shrivel. The plants look scorched and brittle overnight. After a hard freeze, the stems collapse as the chilled tubers below ground go dormant. The spent plants can be cut down to 1-2 inches above soil level once growth stops.
In zones 8 and warmer, tubers can be left in the ground and mulched to overwinter. Anywhere colder, they must be dug and stored in a frost-free place until replanting in spring to get them through winter. Either way, dahlias will resprout the following season from the tubers.
Off-Season Storage
For gardeners who lift and store dahlia tubers over winter, it’s important to check on them periodically while dormant. Keep the tubers at 35-50 degrees Fahrenheit. They are often packed in slightly moist sawdust, wood shavings, vermiculite, peat moss, or sand then stored in cool basement spaces.
Look for any decaying tubers and remove them to prevent rot spreading. Healthy tubers remain firm and plump, never shriveled. By late winter, some new pink growth may be visible at the eyes. This is a great sign of viability. Come spring, viable tubers are ready to be replanted for another season of beauty.
Where Can You Grow Dahlias?
Dahlias can be grown in all zones in the United States. Dahlias are perennial, growing back from the same tuberous root system year after year. However, they are only cold hardy in zones 8-11, and are generally only left in the ground to overwinter in climates where there is no winter freeze. In cooler zones, they can be grown as annuals, or the tubers can be dug and stored for winter and re-planted in spring.
Choose a location with good light. Dahlias require full sun, with 6 or more hours of sunlight daily. Less sun will result in decreased flowering. They need rich, but well-drained soil. They perform best in temperate climates, and in the hottest climates, they should be grown in areas where they can get relief from the hottest afternoon sun.
To learn more about how to plant Dahlia tubers, see our guide: How To Grow Dahlias
Where Do Dahlias Come From?
Dahlias are native to Mexico and South America, and they have a long and intriguing history of capturing the heart of people around the world. Indigenous people grew Dahlia tubers as a source of food and medicine.
Dahlias, or acoctili as they were originally known, were documented by the Spanish in the 1500s, and eventually traveled to Europe by the 1700s. In time, they even charmed Marie Antoinette and became known as a symbol of commitment, dignity, and elegance.
Over the centuries, plant breeders have developed thousands of variations of these beautiful blooms.
5 dahlia growing tips in 5 minutes
FAQ
Do dahlias come back every year?
The tubers that grow beneath the ground are unharmed and can live to perform again year after year given a little care from you. Some lift dahlia tubers and store them over winter, then replant the following spring. Others in milder areas leave them in the ground.
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.
What does a single dahlia plant look like?
Unlike the typically dense clusters of petals that most Dahlias feature, Single Dahlia flowers have a daisy-like form, with broad petals surrounding a central disc.
Are dahlias better in pots or the ground?
Do dahlias grow better in pots or in the ground? Dahlias grow well in pots and in the ground, but bear in mind that it’s easier to move potted dahlias undercover over winter, than it is to lift tubers.