Dahlias, also known as garden dahlias, and botanically classified under the genus Dahlia, are vibrant, tuberous perennials that bring a spectacular display of color and form to any garden. These captivating blooms, related to sunflowers, zinnias, and chrysanthemums, offer an incredible range of shapes, sizes, and hues, making them a favorite among gardeners and floral enthusiasts alike.
At Gardencenterpoint.com, we believe dahlias are more than just flowers; they’re a gateway to a more beautiful and fulfilling gardening experience. This comprehensive guide will delve into the fascinating world of dahlias, covering everything from planting and care to showcasing a diverse selection of varieties and even guiding you on where to purchase top-quality tubers. Continue reading to explore the optimal methods for nurturing these flowers, selecting the ideal dahlia varieties, and even sourcing dahlia tubers for your own garden.
What are Dahlias? An Overview
Dahlias are a genus of bushy, tuberous, herbaceous perennial plants native to Mexico and Central America. They belong to the Asteraceae (or Compositae) family, also known as the daisy family. A defining feature of dahlias is their incredible diversity. They come in a vast array of colors, sizes, and flower forms, ranging from tiny pompons to giant dinner-plate blooms. The flowers are borne on stems that can range from 12 inches to over 6 feet tall, depending on the variety. Dahlias are known for their long blooming season, typically starting in mid-summer and continuing until the first frost.
| Common name | Dahlia, Garden Dahlia |
| Botanical name | Dahlia (Genus) |
| Family | Asteraceae (Compositae) |
| Genus | Dahlia |
| Species | Varies greatly (thousands of cultivars) |
| Origin | Mexico, Central America |
| Native | No (Cultivated varieties globally) |
| Life cycle | Perennial (tender perennial in colder zones) |
| Plant type | Tuberous, Herbaceous |
| Hardiness zone | 8-11 (commonly grown as annuals in zones 3-7) |
| Sunlight | Full Sun (6-8 hours minimum) |
| Maintenance | Medium to High |
| Water | Moderate to High (consistent moisture) |
| Drainage | Well-Drained |
| Spacing | 1-3 ft. (depending on variety) |
| Flowering period | Summer to Fall (until first frost) |
| Height | 1 ft. to 6+ ft. (depending on variety) |
| Growth rate | Moderate to Fast |
| Flower color | Wide range (nearly all colors except true blue); includes bicolors, blends |
| Stem color | Green, sometimes reddish or purplish |
| Flower benefit | Long Bloom Season, Showy Blooms, Excellent Cut Flowers |
| Garden style | Cottage, Cutting Garden, Border, Container |
| Uses | Ornamental, Cut Flowers, Exhibition |
| Toxicity | Mildly toxic to pets if ingested(according to ASPCA) |
| Soil pH | Slightly Acidic to Neutral (6.5-7.0) |
| Fertilizer | Low-Nitrogen (e.g., 5-10-10 or 10-20-20) |
| Propagation | Tuber division, Stem cuttings (less common) |
| Pests | Aphids, Spider mites, Slugs, Snails, Earwigs, Thrips |
| Diseases | Powdery mildew, Gray mold (Botrytis), Dahlia smut, Viral diseases |
Dahlia Origins and History
The history of dahlias traces back to the Aztecs, who cultivated them for food, ceremonial, and medicinal purposes. The tubers were used as a food source, and the hollow stems were even used for water pipes. Spanish conquistadors encountered dahlias in the 16th century, and the first seeds and tubers were sent back to Europe in the late 18th century. The plant was named after Anders Dahl, a Swedish botanist. Initially, dahlias were primarily grown as a food crop, but their stunning flowers soon captured the attention of plant breeders. By the 19th century, extensive hybridization efforts were underway, resulting in the thousands of dahlia varieties we have today.
Dahlia Symbolism and Meaning
Dahlias carry a variety of symbolic meanings, often associated with inner strength, change, creativity, and dignity. In the Victorian language of flowers, dahlias represented a lasting bond and commitment between two people. Different colors also carry specific meanings. For example, red dahlias symbolize power and love, while white dahlias represent purity and innocence. Pink dahlias are often associated with kindness and grace.
How to Grow Dahlias
Growing dahlias can be a rewarding experience, even for beginner gardeners. With the right approach, you can enjoy a stunning display of blooms throughout the summer and fall.
Choosing the Right Location
Dahlias thrive in sunny locations that receive at least 6-8 hours of direct sunlight per day. Morning sun is particularly beneficial. They also prefer well-drained soil that is rich in organic matter. Avoid planting dahlias in areas with poor drainage or heavy clay soil, as this can lead to tuber rot. A slightly acidic to neutral soil pH (6.5-7.0) is ideal.
Preparing the Soil
Before planting, amend the soil with compost or well-rotted manure to improve drainage and fertility. This will provide the dahlias with the nutrients they need for healthy growth and abundant blooms. A soil test can help determine if any additional amendments are needed. Incorporate the organic matter into the soil to a depth of at least 12 inches.
Planting Dahlia Tubers
When to Plant:
The best time to plant dahlia tubers is after the last frost has passed and the soil has warmed up to at least 60°F (15°C). This typically occurs in late spring or early summer, depending on your climate. Planting too early in cold, wet soil can cause the tubers to rot.
Planting Depth and Spacing:
Plant dahlia tubers 4-6 inches deep, with the “eyes” (growth buds) facing upwards. Space the tubers 1-3 feet apart, depending on the mature size of the variety. Larger varieties will require more space.
Step-by-Step Planting Instructions:
- Dig a hole that is slightly larger than the tuber.
- Place the tuber in the hole with the eyes facing up.
- Backfill the hole with soil, gently firming it around the tuber.
- Water thoroughly after planting.
- Avoid over watering until the shoots emerge.
Watering Dahlias
Dahlias need consistent moisture, especially during dry periods. Water deeply once or twice a week, providing about 1 inch of water per week. Avoid overhead watering, as this can promote fungal diseases. Water at the base of the plant to keep the foliage dry. Using a soaker hose or drip irrigation system is an excellent way to provide consistent, even moisture.
Fertilizing Dahlias
Dahlias are heavy feeders and benefit from regular fertilization. Use a low-nitrogen fertilizer, such as a 5-10-10 or 10-20-20 formula. High-nitrogen fertilizers can promote excessive foliage growth at the expense of flowers. Apply the fertilizer according to the package directions, typically every 4-6 weeks during the growing season. A side-dressing of compost or well-rotted manure in mid-summer can also provide a nutrient boost.
Staking Dahlias
Many dahlia varieties, especially those with large flowers, require staking to prevent them from flopping over. Install stakes at planting time, or shortly after the shoots emerge. Use sturdy stakes, such as bamboo canes or metal stakes, and tie the stems loosely to the stakes with twine or soft plant ties. As the plants grow, continue to tie the stems to the stakes for support.
Pinching and Disbudding
Pinching and disbudding are techniques used to promote bushier growth and larger flowers. Pinching involves removing the growing tip of the main stem when the plant is about 12 inches tall. This encourages the plant to branch out, resulting in more flowers. Disbudding involves removing the side buds that form along the stem, leaving only the terminal bud. This directs the plant’s energy into producing a single, larger flower.
Pest and Disease Control
Dahlias are relatively pest and disease-free, but they can be susceptible to certain problems. Common pests include aphids, spider mites, slugs, and snails. Diseases can include powdery mildew, gray mold, and viral diseases. Regularly inspect your plants for signs of pests or diseases. Handpick pests, use insecticidal soap or horticultural oil for aphids and spider mites, and use slug and snail bait as needed. To prevent diseases, ensure good air circulation, avoid overhead watering, and remove any infected plant material promptly.
Overwintering Dahlias
In colder climates (zones 7 and below), dahlias are not hardy and need to be lifted and stored for the winter.
Lifting Tubers:
After the first frost has blackened the foliage, carefully dig up the tubers with a garden fork. Be careful not to damage the tubers. Cut the stems back to about 4-6 inches.
Cleaning and Storing Tubers:
Gently brush off any excess soil from the tubers. Allow the tubers to dry in a well-ventilated area for a few days. Once dry, store the tubers in a cool, dry, and dark place, such as a basement or garage, where the temperature remains between 40-50°F (4-10°C). Pack the tubers in a container filled with peat moss, vermiculite, or sawdust. Check the tubers periodically throughout the winter for signs of rot or shriveling. Discard any damaged tubers.
Dahlia Varieties: A World of Choice
One of the most exciting aspects of growing dahlias is the incredible variety of flower forms, sizes, and colors available. There are thousands of named cultivars, and new ones are introduced every year.
Classification of Dahlias
The American Dahlia Society (ADS) classifies dahlias into several groups based on flower form. Here are some of the main classifications:
- Single-flowered Dahlias: These dahlias have a single row of petals surrounding a central disc.
- Anemone-flowered Dahlias: These dahlias have a central cluster of tubular florets surrounded by one or more rows of flat ray florets.
- Collerette Dahlias: These dahlias have a single row of outer petals, a ring of smaller “collar” petals, and a central disc.
- Waterlily Dahlias: These dahlias have broad, flat petals that resemble water lilies.
- Decorative Dahlias: These dahlias have fully double flowers with broad, flat petals that are often recurved.
- Ball Dahlias: These dahlias have fully double, ball-shaped flowers with petals that are rounded and involute.
- Pompon Dahlias: These dahlias are similar to ball dahlias but are smaller and more tightly formed.
- Cactus Dahlias: These dahlias have fully double flowers with narrow, pointed petals that are rolled outwards.
- Semi-cactus Dahlias: These dahlias have a combination of cactus and decorative characteristics.
- Miscellaneous Dahlias: This category includes dahlias that don’t fit neatly into the other classifications, such as orchid dahlias and peony dahlias.
Popular Dahlia Varieties
Here are some popular dahlia varieties that are widely available:
- ‘Cafe au Lait’: A stunning decorative dahlia with large, creamy blush-pink flowers.
- ‘Bishop of Llandaff’: A striking peony-flowered dahlia with dark red foliage and bright red flowers.
- ‘Karma Choc’: A unique decorative dahlia with dark chocolate-burgundy flowers.
- ‘Thomas A. Edison’: A classic decorative dahlia with large, deep purple flowers.
- ‘Labyrinth’: An eye-catching decorative dahlia, celebrated for its unique and intricate flower form. The petals of ‘Labyrinth’ exhibit a fascinating blend of colors, typically featuring a mix of coral, pink, and peach hues.
These are just a few examples of the many beautiful dahlia varieties available. Experiment with different types to find your favorites.
Best Dahlias for Cutting
Dahlias make excellent cut flowers, adding a touch of elegance and vibrancy to any arrangement.
Characteristics of Good Cut Flower Dahlias
- Long, strong stems: Look for varieties with stems that are at least 18 inches long.
- Good vase life: Choose varieties that are known to last for at least 5-7 days in a vase.
- Tight flower heads: Select flowers that are fully open but still firm to the touch.
- Minimal petal drop: Avoid varieties that are prone to dropping their petals quickly.
Top Dahlia Varieties for Cutting
- ‘Cafe au Lait’
- ‘Karma Choc’
- ‘Thomas A. Edison’
- ‘Labyrinth’
- ‘Cornel Bronze’
- ‘Penhill Watermelon’
- ‘Jowey Winnie’
- ‘Linda’s Baby’
Tips for Harvesting and Conditioning Dahlia Flowers
- Cut dahlias in the early morning or late evening when the temperatures are cool.
- Use sharp, clean clippers or a knife.
- Cut the stems at an angle.
- Remove any leaves that will be below the waterline in the vase.
- Place the cut stems in a bucket of cool water immediately.
- Recut the stems under water before arranging them in a vase.
- Add flower food to the vase water to prolong the life of the flowers.
- Change the water every day or two.
Buy Dahlia Tubers
Finding healthy, high-quality dahlia tubers is essential for successful growing.
Where to Buy Dahlia Tubers
- Local Nurseries and Garden Centers: These are a good option for finding locally adapted varieties.
- Online Retailers: Many online retailers specialize in dahlias and offer a wide selection of varieties.
- Specialty Dahlia Growers: These growers often have rare and unusual varieties that are not available elsewhere. Check the American Dahlia Society website for a list of suppliers.
What to Look for When Buying Dahlia Tubers
- Firm, plump tubers: Avoid tubers that are soft, shriveled, or moldy.
- Visible eyes: Make sure the tubers have at least one or two visible eyes (growth buds).
- No signs of damage: Check for any cuts, bruises, or other damage.
- Variety labeling: Ensure the tubers are clearly labeled with the variety name.
Dahlia Society and Resources American Dahlia Society (ADS)
The American Dahlia Society (ADS) is a non-profit organization dedicated to promoting the cultivation and appreciation of dahlias. The ADS website (dahlia.org) is an excellent resource for information on dahlia varieties, growing tips, shows, and events. It also provides a directory of local dahlia societies and suppliers. Gardencenterpoint recommends joining the ADS to connect with other dahlia enthusiasts and expand your knowledge.
Other Dahlia Societies and Organizations
Many regional and local dahlia societies exist throughout the United States and other countries.
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