How to Plant Dahlia Plants

Dahlias are a gardener’s delight. These flowers have a rich history dating back to the Aztecs, who cultivated them for their medicinal properties. 

The tubers of dahlias were traditionally used to treat skin conditions and digestive issues, while the petals were believed to have anti-inflammatory effects.

Planting dahlias not only enhances the aesthetic appeal of your garden but also attracts pollinators like bees and butterflies. 

Whether you’re an experienced gardener or a novice, growing dahlias can provide a rewarding experience. 

Summary:

  • Plant dahlias after the last frost in well-drained, fertile soil with a pH of 6.2-6.8. Ensure six hours of direct sunlight daily.
  • Water deeply 2-3 times a week and support tall varieties with stakes or cages.
  • Use organic methods to control pests. Adjust light, nutrients, and watering to address common issues.
  • Cut flowers early or late in the day and store tubers properly for winter. 
Dahlia
Dahlia
Scientific Name Dahlia
Common Name Dahlia
Plant type Perennial
Height 30 cm to 2.4 meters
Flower Color red, pink, white, yellow, purple, etc.
Flower Shape Radial symmetry
Bloom Time Mid-summer to first frost
Sunlight Full sun
Soil Requirements Well-drained, fertile soil
Habitat Native to Mexico and Central America

 

Propagation

Seeds

In early spring, use a seed tray filled with fine, well-draining potting compost. Then sprinkle the dahlia seeds evenly across the surface and cover them lightly with a thin layer of compost.

Keeping the soil consistently moist and placing the tray in a warm, sunny spot encourages germination.

Germination usually takes about two weeks. Once the seedlings develop a couple of true leaves, I transplant them into individual pots to give them more room to grow. 

Seeds
Seeds

 

Dividing Clumps of Tubers

In the fall, once the foliage has blackened from the first frost, look for healthy, firm tubers with visible “eyes” or growth points then dig them up.

In early spring, place them indoors in a shallow tray of potting compost. When the shoots reach about 1 inch tall, lift the clump of tubers and divide it into several pieces with both roots and shoots.

Next, pot up each section into a separate container and grow them in a bright, frost-free place until late May or early June. 

Gradually acclimatize the plants to outdoor conditions by hardening them off, then plant them into their flowering positions. 

Dividing Clumps of Tubers
Dividing Clumps of Tubers

 

Cutting Stems

When seeing the first new shoots emerging from the tubers, choose stems that are about 3-4 inches tall.

Use a clean, sharp knife to make a cut just below a leaf node, ensure the cutting has at least two pairs of leaves.

Next, dip the cut end into the rooting hormone to encourage faster root development. I then plant the cutting into a pot filled with moist, well-draining potting compost.

Keeping the soil consistently moist and placing the pot in a bright, frost-free area. In my experience, stem cuttings can produce robust plants faster than growing from seeds.

Cutting Stems
Cutting Stems

 

Growing Dahlia

Preparation

Varieties of Dahlia

There are 42 species and hundreds of dahlia hybrids. I currently have about 20 dahlia plants. 

One of the most stunning varieties I grow is ‘Cafe au Lait,’ known for its large, creamy, almost blush-colored blooms that can reach up to 10 inches in diameter. 

Another favorite is the ‘Bishop of Llandaff,’ which features striking red flowers and dark, almost black foliage. This variety can attracts many bees and butterflies.

Gallery Art Deco’ is a choice for a compact variety. Growing to about 12-16 inches tall, it produces vibrant pink blooms ideal for containers or front borders.

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The ‘Kelvin Floodlight’ is another must-have, with its big, bright yellow blooms. Lastly, the ‘Arabian Night’ offers deep, velvety red flowers that are excellent for cutting gardens.

Varieties of Dahlia
Varieties of Dahlia

 

Looking for a Spot

Choose a location that receives at least six hours of direct sun each day. 

Before planting, you should test the soil pH and adjust it if necessary using lime to raise it or sulfur to lower it. 

Incorporating organic matter like compost or manure significantly improves soil structure and fertility, promoting healthier plants and more vibrant blooms.

 

How to Grow Dahlia In Containers

Medium- to dwarf-size dahlias thrive in containers that provide adequate drainage and space for mature growth, typically a 12×12-inch container. 

When planting, ensure the tubers are positioned with the eyes facing up and covered with a few inches of the soil.

If roots become exposed due to growth, add additional soil around the base of the plant.

How to Grow Dahlia In Containers
How to Grow Dahlia In Containers

 

How to Grow Dahlia Outdoors

Start after the last frost date when soil temperatures reach at least 60°F. Begin by digging a hole 6-8 inches deep in well-draining soil enriched with compost. 

Position the tubers with the eyes facing up, ensuring they’re spaced about 12-18 inches apart to allow for growth. 

Cover the tuber with 2 to 3 inches of soil and as the stem sprouts, fill in with soil until it is at ground level.

Remember that you have to wait until sprouts appear above the soil before watering again. Dahlias typically begin blooming about 8 weeks after planting.

How to Grow Dahlia Outdoors
How to Grow Dahlia Outdoors

Tips: Growing dahlia outdoor can deter deer due to their bitter taste and the texture of their foliage, making them less appealing to deer.

 

Care for Dahlia

Here are main requirements for growing dahlia:

  • Dahlias require full sun, ideally 6-8 hours daily.
  • Regularly prune dahlias to encourage bushier growth and more flowers.
  • Pinch off the top growth when plants reach about 12 inches tall.
  • Use bamboo stakes or cages to gently support tall varieties of dahlias.
  • Feed dahlias regularly with a balanced fertilizer to provide essential nutrients.
  • Water deeply after planting to settle the soil around the tubers. 
  • Space dahlia tubers 12-18 inches apart to allow for ample air circulation.

 

Light

Dahlias thrive in full sun, requiring at least 6-8 hours of direct sunlight daily to flourish. 

However, they can tolerate some light shade, especially in hotter climates where partial shade during the hottest part of the day can benefit the plants.

Adequate sunlight not only promotes photosynthesis and healthy foliage but also encourages the development of large, colorful flowers. 

Sunlight
Sunlight

 

Soil

I often mix in plenty of organic matter like compost or well-rotted manure to enhance soil structure and nutrient content for dahlia. 

Scientific studies back this up, showing that organic matter improves water retention and aeration, crucial for dahlia roots. 

Additionally, I ensure the soil pH stays between 6.2 and 6.8 by regularly testing and adjusting with lime or sulfur as needed. 

 

Water

Drip irrigation directs moisture right to the root zone while keeping the foliage dry, reducing the risk of fungal diseases. 

If you prefer hand-watering, like I often do, it’s best to water deeply once or twice a week to ensure that the roots get enough moisture. 

However, be cautious of overwatering; it can lead to root rot and other issues..

Watering
Watering

 

Temperature and Humidity

Dahlias prefer temperatures between 60°F and 70°F, making them ideal for USDA hardiness zones 8 to 10. 

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I plant mine after the last frost in spring and enjoy their blooms until the first frost in autumn. 

High humidity can lead to fungal issues like powdery mildew, so it’s crucial to maintain good air circulation around the plants. 

 

Fertilizer

In the early growth stages, I use a balanced fertilizer like 10-10-10 every four to six weeks to provide an even supply of essential nutrients. 

As the season progresses, you should switch to a low-nitrogen fertilizer, such as 5-10-10, which helps promote more flowers rather than just foliage. 

It’s important to avoid over-fertilization, which can harm the plants. I usually opt for granular fertilizer, sprinkling it around the base of the plants and gently working it into the soil. 

But you can also use liquid fertilizer during regular watering sessions. 

 

Staking and Supporting

Some dahlia varieties can reach up to six feet tall, and without proper support, they can easily bend or break under the weight of their blooms. 

To avoid this, I install sturdy wooden stakes and place them about a foot away from the tuber to avoid damaging it.

As the dahlias grow, I gently tie the stems to the stakes with soft garden twine, ensuring they have enough room to move slightly, which strengthens their stems.

Staking and Supporting
Staking and Supporting

 

Pruning and Deadheading

Early in the season, I pinch the tips of my dahlia plants when they are about 12 inches tall. 

I use my thumb and forefinger, or sharp scissors to remove the top 1-2 inches of the main stem to encourage bushier growth.

Throughout the blooming season, you need to deadhead or remove spent flowers. 

Besides regularly pruning my dahlias to maintain the desired shape and size, remember to remove weak or damaged stems.

Pruning and Deadheading
Pruning and Deadheading

 

Pests and Diseases

Dahlias can face aphids, slugs, and spider mites. I’ve found that aphids often cluster on the new growth, sucking the sap and weakening the plant. 

Slugs, on the other hand, tend to munch on the leaves, especially at night. Spider mites leave tiny webs and cause speckled, discolored foliage. 

To combat these pests organically, I use insecticidal soap or neem oil, both of which are effective and environmentally friendly.

Pests on Dahlia
Pests on Dahlia

In addition, powdery mildew and bacterial wilt are the most common in dahlias. 

Powdery mildew appears as a white, powdery coating on the leaves, while bacterial wilt causes sudden wilting and collapse of the plant. 

Good air circulation is crucial to prevent these issues, so I make sure to space my plants adequately and avoid overhead watering. 

Diseases on Dahlias
Diseases on Dahlias

 

Common Problems

Poor Blooming

Poor blooming usually stems from insufficient sunlight or a lack of nutrients. 

Dahlias require at least six hours of direct sunlight daily. If your plants aren’t getting enough light, try relocating them to a sunnier spot. 

Besides, try the ratio of fertilizer as I have suggested above to encourage more blooms. Note that over-fertilizing with nitrogen can lead to lush foliage but few flowers.

 

Slow Growth

Inadequate watering or poor soil quality can cause slow growth of dahlias. Ensure you’re watering deeply 2-3 times a week without overwatering.

Additionally, you should add compost and regularly check for and address any infestations or infections. 

 

Rotting Tubers 

Rotting tubers are often caused by overwatering or poor soil drainage. Remember to plant dahlias in well-draining soil and avoid overwatering. 

If you notice rotting tubers, carefully dig them up and inspect. Remove the affected areas with a clean, sharp knife, and dust the healthy parts with fungicide before replanting. 

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Harvest 

The best time to cut flowers is either early in the morning or during cool evenings when the plants are well-hydrated and temperatures are lower. 

Using sharp, clean tools, I make diagonal cuts on the stems to increase the surface area for water uptake, so the flowers stay fresh longer.

To prolong the vase life of your dahlias, you should place the freshly cut stems in a bucket of lukewarm water for a few hours. Adding flower preservatives to the water if needed.

 

Preservation

As winter approaches, I start by cutting back the foliage to about 4-6 inches above the ground to help the plant’s energy focus on the tubers. 

Next, I carefully dig up the tubers and brush off the excess soil, then let them air dry for a few days in a cool, dry place. 

I layer the tubers in a box, ensuring they are completely covered and not touching each other to prevent rot.

Before replanting in the spring, check and discard any tubes that are soft or discolored.

Preservation
Preservation

 

FAQs

Is dahlia easy to grow? 

Yes, dahlias are relatively easy to grow if you provide the right conditions, such as well-draining soil, ample sunlight, and regular watering. They can thrive in a variety of climates and are quite resilient.

 

What are the dahlia growth stages? 

Dahlia growth stages include planting the tuber, sprouting, vegetative growth, budding, flowering, and dormancy. Proper care during each stage ensures healthy growth and abundant blooms.

 

What are dahlia eyes? 

Dahlia eyes are the small, bud-like growth points on the tuber from which new shoots emerge. Each eye has the potential to grow into a new plant.

 

What is a dahlia tuber? 

A dahlia tuber is a swollen part of the plant’s root system used for storing nutrients. Tubers have buds, or “eyes,” that can sprout into new plants.

 

What are dahlia roots? 

Dahlia roots are the fibrous structures that grow from the tuber. They absorb water and nutrients from the soil, supporting the plant’s growth.

 

What are dahlia leaves like? 

Dahlia leaves are typically green, broad, and serrated. They grow in pairs along the stem and help the plant photosynthesize.

 

How large do dahlias grow? 

Dahlia size can vary widely depending on the variety. Some dwarf varieties grow to about 12-16 inches tall, while others can reach up to 6 feet.

 

Do dahlias come back every year? 

Yes. Dahlias are perennial in USDA hardiness zones 8-10. In colder climates, the tubers need to be dug up and stored over winter, then replanted in the spring.

 

How to Plant Dahlia Plants
How to Plant Dahlia Plants

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