Dahlia: Plant, Care, and Propagate Guide

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Dahlias are tuberous perennials that belong to the Asteraceae family. They are known for their large, showy blooms that come in a variety of colors, shapes, and sizes. Dahlias are characterized by their hollow stems, lush foliage, and the ability to produce flowers continuously from mid-summer to the first frost.

Dahlias became particularly popular during the Victorian era, symbolizing elegance and sophistication. They were a staple in many formal gardens of the time. In Mexico, dahlias are the national flower and hold cultural significance. They symbolize dignity and instability, reflecting the diverse and resilient nature of the country.

Botanical Name
Dahlia pinnata
Plant Type
Tuberous perennials
Family
Asteraceae
Height
Vary in height from 1 to 6 feet
Foliage
Typically green and can be either smooth or slightly serrated
Bloom Time
Mid-summer to the first frost
Climate
Thrive in temperate climates
Sun Exposure
Full sun to partial shade
Soil Requirements
Well-drained, fertile soil with a pH level between 6.0 and 7.5
Hardiness Zones
USDA zones 8-11
Flowering
Come in a wide range of colors, including red, pink, yellow, orange, purple, and white
Special Features
Attract pollinators such as bees and butterflies. They are also deer-resistant, making them a good choice for gardens in areas with deer populations
Toxicity
Considered non-toxic to humans and pets

How to Care for Dahlia?

Caring for dahlias goes beyond their aesthetic appeal. Proper care for dahlias is essential for their health, longevity, and the overall beauty they bring to any environment.

Water

Watering dahlias requires careful attention to timing, frequency, and amount. It is best to water dahlias in the early morning to allow the foliage to dry out during the day, reducing the risk of fungal diseases. Dahlias should be watered deeply 1-2 times a week, ensuring the soil is consistently moist but not waterlogged. Each watering session should deliver about 1-1.5 inches of water, enough to reach the roots deeply. As the season progresses and temperatures rise, especially in midsummer, you might need to increase watering frequency. However, as fall approaches and the plants start to go dormant, gradually reduce watering to allow the tubers to harden off in preparation for winter.

Sunlight

Dahlias thrive in full sun, requiring a minimum of six hours of direct sunlight each day to flourish. When selecting a planting site, prioritize locations with ample sunlight exposure, preferably with southern or western orientations. Insufficient light can lead to weak, leggy growth and diminished flower production.

In regions with intense summer heat, some dahlia varieties benefit from partial shade during the hottest part of the day to prevent sunburn on petals and foliage. For gardeners in cooler climates or those with limited access to full sun, consider utilizing techniques such as planting dahlias in containers that can be moved to sunnier spots throughout the day or supplementing natural light with artificial lighting, such as grow lights, to extend the growing season.

Fertilizer

Incorporating a balanced fertilizer into the soil before planting provides a solid foundation for the dahlias’ growth. A general-purpose fertilizer with equal parts nitrogen, phosphorus, and potassium (N-P-K) is suitable for dahlias.

As dahlias begin to grow and produce foliage, they benefit from regular fertilization throughout the growing season. Many gardeners adopt a schedule of applying fertilizer every four to six weeks, starting in early spring and continuing until late summer or early fall. However, it’s essential to adjust fertilization frequency and dosage based on
the specific needs of the dahlias and the soil’s nutrient content.

During the flowering stage, dahlias have increased nutrient demands to support blooming and maintain plant vigor. Therefore, it’s advisable to switch to a fertilizer higher in phosphorus, the nutrient responsible for promoting flowering and fruiting. A fertilizer with a higher middle number in its N-P-K ratio, such as a 5-10-5 or 10-20-10 formulation, can encourage abundant flower production and vibrant colors in dahlias.

Soil

Dahlias thrive in soil that drains well. A mixture of sand, silt, and clay, loamy soil is ideal. If your soil is too dense, you can improve its texture by adding sand, peat moss, or manure. Dahlias thrive in a neutral soil pH of around 6.5. Mixing compost into the soil can provide the necessary nutrients for dahlias.

Prune

When the dahlia plant reaches about 8 to 12 inches in height, Use clean, sharp scissors or pruners to cut off the top 3-4 inches. Regularly remove spent flowers by cutting the flower stem just above a leaf node or bud. If your dahlia plant becomes too congested, thin out the weaker stems to improve air circulation and overall plant health. Remove any spindly or overcrowded shoots. To get larger blooms, remove the smaller buds that develop behind the main, central bud. After the first frost going end-of-season pruning, cut back the stems to about 6 inches from the ground.

Temperature & Humidity

Dahlias prefer daytime temperatures between 70-85°F (21-29°C). Night temperatures should ideally be cooler, around 55-60°F (13-16°C). Dahlias are sensitive to frost. They should be planted after the danger of frost has passed and dug up or heavily mulched before the first frost in the fall if grown in colder climates. Dahlias do well in average humidity levels. They require a humidity level of approximately 90% during storage.

Container

Different materials can be used for containers, such as terra cotta, plastic, cement, and untreated wood. Choose a container that is at least 12-18 inches deep and 12-18 inches in diameter. This allows ample space for the root system and tubers to develop. A container with a volume of at least 5 gallons is ideal. Ensure the container has proper drainage holes to prevent water from standing, which can lead to root rot and fungal diseases.

Type of Dahlias

  • Dahlia ‘Yellow Hammer’ is a single-flowered Dahlias. These have a single row of petals surrounding a central disc.
  • Dahlia ‘Mambo’ is anemone-flowered Dahlias. These have one or more rows of flat petals with a dense central group of elongated tubular florets.
  • Dahlia ‘Honka’ belongs to Orchid-flowered Dahlias. These have open centers and petals that curl inward or backward.
  • Dahlia ‘Karma Corona’ is a variety of Cactus Dahlias. These have narrow, pointed petals that roll back and form a spiky appearance.
  • Pompon Dahlias are similar to ball dahlias but smaller, with more tightly packed petals, such as Dahlia ‘Rocco’.
  • Dahlia ‘Gerrie Hoek’ is a waterlily dahlia with broad, flat petals resembling water lilies.
  • Dinnerplate Dahlias ‘Café au Lait’ is a decorative dahlia known for its exceptionally large flowers.

When and how to plant the Dahlias

Planting dahlias offers a kaleidoscope of colors and shapes to adorn the landscape. These resilient flowers thrive in well-drained soil and plenty of sunlight, rewarding attentive caretakers with prolific blooms throughout the summer and into the fall. From dwarf varieties perfect for borders to towering dinner plate dahlias that steal the show, there’s a dahlia for every garden size and style.

Plant dahlias after all danger of frost has passed and the soil temperature is consistently at or above 60°F (16°C). In most areas, this will be in the spring, typically from April to June.

  1. Choose a sunny spot with at least 6 to 8 hours of direct sunlight, preferably morning sun.
  2. Ensure the soil is rich and well-draining. Amend heavy clay soil with organic matter like compost.
  3. Plant the tubers with the growing points, or “eyes,” facing up, about 6 to 8 inches deep.
  4. Provide ample space between plants, about 18 to 24 inches apart, depending on the variety.

How to Propagate Dahlia

Propagating dahlias can be done through stem cuttings, tuber division, or seeds. Each method has its advantages. Stem cuttings and tuber division produce plants identical to the parent, while seeds can result in new and unique varieties.

Stem Cuttings

  1. Prepare the Tubers: Plant the tuber in moist soil to wake it up. This will encourage the growth of shoots.
  2. Take Cuttings: Once the shoots are about 3-4 inches long, cut them off just above the tuber.
  3. Plant the Cuttings: Insert the cuttings into a pot with regular potting soil up to where the first leaves are.
  4. Care for the Cuttings: Keep the soil moist and warm. Mist the cuttings daily or cover them with a plastic bag to maintain humidity.
  5. Root Development: In about three weeks, the cuttings will have formed roots. You can then pot each cutting individually.

Tuber Division

  1. Dig Up the Tubers: After the first frost, dig up the dahlia tubers.
  2. Divide the Tubers: Carefully separate the tubers, ensuring each division has at least one “eye” (growing point).
  3. Store the Tubers: Store the divided tubers in a cool, dry place over the winter.
  4. Plant in Spring: Plant the tubers in the ground or pots in the spring after the last frost.

Seeds

  1. Collect Seeds: Harvest seeds from the dahlia flowers at the end of the growing season.
  2. Sow Seeds: Sow the seeds indoors in early spring.
  3. Transplant Seedlings: Once the seedlings are large enough to handle, transplant them into individual pots.
  4. Plant Outdoors: Plant the seedlings outdoors after the last frost.

Common Pests & Plant Diseases

Dahlias are susceptible to various diseases and pests that can affect their growth and blooming. Common diseases include bacterial wilt and soft rot, which can cause wilting, yellowing, and rotting of the plants. To prevent these diseases, ensure proper drainage, avoid overwatering, and remove infected plants promptly.

Pests such as aphids, slugs, and snails can also damage dahlias by feeding on their leaves and flowers. Preventive measures include using physical barriers like copper tape or eggshells, maintaining a tidy garden, and applying organic insecticides if necessary.

FAQs

What Do Dahlias Symbolize?

Dahlias symbolize elegance, inner strength, creativity, and dignity. They are often associated with commitment and a lasting bond.

What is Special About Dahlias?

Dahlias are special due to their incredible diversity in color, form, and size. They offer a long blooming period and are excellent for cut flowers and garden displays.

Why are Dahlias So Expensive?

Dahlias can be expensive due to the extensive breeding and cultivation required to produce unique varieties. The labor-intensive process of propagating and maintaining healthy plants also contributes to the cost.

Do Dahlias Smell Nice?

Dahlias typically do not have a strong fragrance. Their appeal lies more in their vibrant colors and striking forms rather than their scent.

Do Dahlias Last Long?

Dahlia flowers can last up to a week as cut flowers if kept in fresh water. In the garden, they continue to bloom from midsummer until the first frost, providing continuous color.

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