Dahlia: Plant Care and Growing Guide

Choosing Dahlias

There are thousands of varieties of Dahlias (!!!), and they are all classified by the shape, size, and color of their flowers.

When choosing dahlias for your garden or landscape, there are a few things to consider:

Size: There are dwarf Dahlia varieties growing as low as 12 inches (30 cm): these are perfect for containers or the front of borders. Most Dahlias grow up to 4 feet (120 cm), and some varieties can easily reach 6 feet in height (180 cm). They will need staking for support.

Color: Dahlias come in a wide range of colors, from bright and bold to soft and subtle. Consider the color scheme of your garden or landscape and choose dahlias that will complement or enhance the overall look and feel.

Shape and texture: Dahlia flowers come in a wide range of shapes and textures, from single petals to multiple rows and smooth to ruffled. Consider the overall style and aesthetic of your garden or landscape when choosing the shape and texture of your dahlia plants.

Pollinators: If you wish to attract pollinators to your garden, select single-flowered or open-centered dahlia types.

Disease resistance: Some dahlia varieties are more resistant to diseases than others. When choosing dahlias, look for varieties that are known for their disease resistance, which will help to ensure that your plants stay healthy and productive throughout the growing season.

When to Plant Dahlia Flowers

The timing of planting dahlia flowers depends on your location and climate. In general, dahlias are planted after the last frost date in your area when the soil has warmed up and the weather is consistently warm. Ideally, soil temperatures should be at least 60°F (15.5°C) at planting time, and daytime temperatures should be consistently above 60°F (15.5°C) as well.

If you live in a warmer climate with mild winters, you can plant dahlias in the early spring for summer blooms. In cooler climates, wait until the danger of frost has passed in the late spring or early summer.

You can also start dahlias indoors 4-6 weeks before the last frost date in your area, then transplant them outdoors once the soil has warmed up and the danger of frost has passed.

How to Plant Dahlias

Choose a location: Select a sunny location with well-draining soil.

Prepare the soil: Amend the soil with compost or well-rotted manure to improve soil quality and drainage.

Dig a hole: Dig a hole that is twice the width of the dahlia tuber and about 6-8 inches deep (15-20 cm).

Plant the tuber: Place the dahlia tuber in the hole with the “eye” (the point where the stem will emerge) facing up. Cover the tuber with soil, leaving the eye exposed.

Spacing: Optimal spacing for dahlias is essential for healthy growth, providing adequate air circulation, minimizing disease risk, and allowing each plant to reach its full potential:

• Large Dahlias (like Dinner Plate varieties): Space 24-36 inches (60-90 cm) apart. These dahlias can grow up to 4-6 feet tall with large blooms, so they need ample room to expand and for good air circulation.

• Medium Dahlias: Space 18-24 inches (45-60 cm) apart. This spacing works well for medium-sized varieties, allowing sufficient room for growth without crowding.

• Compact or Dwarf Dahlias: Space 12-18 inches (30-45 cm) apart. Smaller varieties are perfect for borders, containers, or smaller garden spaces, and this spacing supports airflow while maximizing display impact.

Water: Wait until sprouts have emerged above the soil before watering.

Add support: Depending on the variety, dahlias may need staking or other support to prevent them from falling over. Add a support structure at planting time to avoid damaging the roots later on.

Where to Plant Dahlia Tubers

Hardiness: Dahlias are tender perennials and are hardy in USDA hardiness zones 8-11, where temperatures do not typically drop below 20°F (-6°C) in the winter. In cooler climates, dahlias are often grown as annuals or lifted and stored over the winter to protect them from freezing temperatures.

Light: Dahlias prefer full sun. When choosing a location to plant your dahlias, look for a spot that gets at least 6 hours of direct sunlight each day. The soil should be well-draining

Soil: Dahlias thrive in well-draining soil, as dahlias do not like to sit in wet soil. If your soil is heavy or poorly drained, consider planting your dahlias in raised beds or containers filled with well-draining soil.

Space: Dahlia plants can grow quite tall, so be sure to plant them in a location where they will have room to grow and will not shade out other plants in your garden or landscape.

Protection: In areas with high winds, consider planting dahlias near a fence or building for protection.

Landscaping with Dahlias

Dahlias are a versatile and beautiful addition to any landscape and can be used in a variety of ways to add color and interest. Here are a few ways to use dahlias in the landscape:

Garden beds: Plant dahlias in garden beds to add color and interest to your landscape. They pair well with a variety of companion plants.

Borders: Use dahlias to create borders along garden beds or walkways. Their tall, upright habit makes them a great choice for adding structure to your landscape.

Containers: Plant dahlias in containers to add color and interest to patios, decks, or other outdoor spaces. They are particularly well-suited for large containers that can accommodate their size.

Cut flowers: Dahlias are a popular choice for cut flowers and floral arrangements. Plant them in a cutting garden or incorporate them into your existing garden beds to have fresh blooms to cut and enjoy throughout the growing season.

Focal point: Use dahlias as a focal point in your landscape by planting them in a prominent location, such as the center of a garden bed or at the end of a walkway. Their large, showy blooms will draw the eye and add visual interest to your landscape.

Dahlia Care

Dahlias are relatively easy to care for but require regular attention to keep them healthy and produce beautiful blooms throughout the growing season. Here are some tips:

Water: Dahlias require regular watering to thrive, especially during hot and dry periods. Water deeply 2 or 3 times a week to keep the soil moist but not waterlogged.

Pinching: Pinch back new growth when the dahlia is a foot high (30 cm) to promote a compact, bushy growth

Fertilize: Dahlias benefit from regular fertilization to support healthy growth and blooming. Feed monthly from mid-summer until early fall with bloom-type fertilizer to ensure full bloom.

Deadhead: Remove spent blooms regularly to promote continued blooming and prevent the plant from diverting energy to seed production.

Stake: Depending on the variety, dahlias may need staking or other support to prevent them from falling over.

Overwintering Dahlia Tubers

In cooler climates, dahlias are often lifted and stored over the winter to protect them from freezing temperatures. Here are the steps to overwinter dahlias:

Wait for the foliage to die back: Wait to dig up dahlia tubers until the top growth dies back or is killed by the first hard frost.

Dig up the tubers: Use a garden fork to gently lift the dahlia tubers from the soil, taking care not to damage them.

Trim the foliage: Cut the stems back to about 6 inches (15 cm) and remove any remaining leaves or debris.

Clean and dry: Clean off any excess soil and allow the tubers to dry in a warm, dry location for a few days.

Store in a cool, dry place: Once the tubers are dry, store them in a cool, dry place for the winter. You can place them in a box or a paper bag filled with dry peat moss or vermiculite. Store them at a temperature between 40 and 50°F (4.5 to 10°C) to prevent them from drying out or freezing.

Check periodically: Check on your stored tubers periodically throughout the winter to make sure they are still healthy and firm. Discard any tubers that have become soft or rotten.

Plant in the spring: In the spring, after the danger of frost has passed, you can plant your stored tubers in the garden and enjoy beautiful dahlias once again.

How to Propagate Dahlia

There are several ways to propagate dahlias, including dividing tubers, taking stem cuttings, and sowing seeds. Here are the steps for each method:

Dividing tubers: In the spring, when new shoots appear on the tubers, you can divide them into smaller pieces using a sharp knife or garden shears. Each division should have at least one eye or growing point. Plant the divisions in well-draining soil and water them regularly until they establish.

Taking stem cuttings: In mid-summer, when the dahlia plants are in full growth, you can take stem cuttings from the tips of the plants. Cut a stem that is 4-6 inches (10-15 cm) long and remove the leaves from the bottom half. Dip the cut end in rooting hormone and plant it in a pot filled with moist potting soil. Keep the soil moist and provide bright, indirect light until the cutting roots and new growth appears.

Sowing seeds: In the spring, you can sow dahlia seeds indoors or outdoors, depending on your climate. Sow the seeds in well-draining soil and keep the soil moist. When the seedlings are large enough to handle, transplant them into larger containers or into the garden.

Pests and Diseases

Dahlias are generally relatively disease and pest-resistant, but there are a few common issues to watch out for:

Aphids: These tiny insects can infest the leaves and buds of dahlias, causing yellowing and distorted growth. Use insecticidal soap or neem oil to control them.

Botrytis blight: This fungal disease can cause gray or brown fuzzy mold on the leaves, flowers, and stems and can lead to stem rot and plant death. You can prevent botrytis blight by ensuring good air circulation, avoiding overhead watering, and applying a fungicide.

Earwigs: Earwigs feed on the petals and can cause damage to the blooms. Use traps, cultural controls, natural predators, or organic pesticides.

Powdery mildew: This fungal disease can affect the leaves and stems of dahlias, causing a white powdery coating. Improve air circulation and use a fungicide to control it.

Slugs and Snails: These pests can damage young dahlia shoots and leaves. Use slug bait or copper tape around the base of the plants to deter them.

Spider mites: These pests can also infest dahlias, causing webbing and yellowing leaves. Use insecticidal soap or neem oil to control them.

Thrips: They feed on the petals and can cause damage to the blooms. Use cultural controls, natural predators, or organic pesticides.

Learn about pests and diseases that could harm your dahlias and tips for prevention and treatment.

To prevent these issues, it’s important to maintain healthy plants by providing adequate water, nutrition, and air circulation, as well as removing any damaged or diseased foliage promptly. With proper care and attention, your dahlias should remain healthy and beautiful throughout the growing season.

Companion Plants for Dahlias

Dahlias have a wide range of companion plants that can complement their beauty, including perennials and ornamental grasses.

Frequently Asked Questions

Are dahlias perennial?

Yes, dahlias can be perennial plants depending on the climate and growing conditions. In warmer regions, such as USDA hardiness zones 8-11, dahlias can overwinter and regrow from their underground tubers for multiple seasons.

Do dahlias come back every year?

Dahlias can come back every year if they are grown in regions with mild winters or if they are properly overwintered in colder regions.

Why are dahlias poisonous?

Dahlias are not considered poisonous to humans, but their tubers and leaves can be toxic to pets and livestock if ingested in large quantities. The toxic component in dahlias is hydrocyanic acid, which can cause symptoms such as vomiting, diarrhea, and abdominal pain in animals.

Where is the best place to plant dahlias?

The best place to plant dahlias is in a location that receives full sun for at least 6 hours a day and has well-draining soil. Dahlias are heat-loving plants that thrive in warm, sunny locations, and they need good drainage to prevent the tubers from rotting.

What does a dahlia symbolize?

Dahlias have a variety of symbolic meanings depending on the color and context: gratitude and appreciation, inner strength and creativity, commitment, and partnership, or luxury and elegance.