How to Grow Dahlias

Dahlias are stunning, vibrant flowers that bring color and texture to any garden. With blooms ranging from small pompoms to dinner-plate-sized blossoms, these versatile plants are a favorite among flower enthusiasts. Whether you’re planting in containers, flower beds, or borders, learning how to grow dahlias can be a rewarding experience — especially for beginner gardeners.

In this comprehensive guide, we’ll walk you through everything you need to know about growing dahlias successfully, from choosing the right variety to harvesting beautiful blooms.

Why Grow Dahlias?

Brilliant colors: Dahlias come in a rainbow of hues, from soft pastels to fiery reds and deep purples.
Long flowering season: They bloom from midsummer well into autumn.
Versatile use: Perfect for garden borders, containers, and cut flowers.
Variety: From dwarf types suitable for pots to towering giants that command attention.

If you’re interested in other colorful blooms, check out our guide to growing lavender for more inspiration.

Choosing the Right Location for Your Dahlias

Sunlight and Shelter

Dahlias thrive in full sun, requiring at least 6 hours of direct sunlight daily. A south or west-facing border is ideal.
Choose a sheltered spot protected from strong winds to prevent stems from breaking.

Soil Requirements

Dahlias prefer fertile, moist but well-drained soil.
Enrich your soil with organic matter like well-rotted manure or compost.
For heavy clay soils, improve drainage by mixing in horticultural grit or sand.
If planting in containers, use a high-quality, peat-free multipurpose compost mixed with organic matter.

If you’re unsure about your soil, our step-by-step soil testing guide will help you get started.

Getting Started: Planting Dahlia Tubers

When to Plant

Plant dahlias after the last frost when the soil has warmed, typically from mid to late May.
In milder climates, tubers can be planted in early April if the soil is not frozen.

Preparing Tubers

Purchase top-quality dahlia tubers from garden centers or online starting in February.
Before planting outdoors, you can start tubers indoors in early April:
Place tubers in pots filled with moist, peat-free compost.
Keep them in a light, frost-free place like a greenhouse or sunny windowsill.
Shoots should appear in about 5 weeks.

Planting Technique

Dig a hole about 4 to 6 inches (10-15 cm) deep.
Place the tuber on its side with the growing eye or shoot facing upward.
Cover with soil so the tuber is about 1-2 inches below the surface.
Space plants about 45-60 cm (18-24 inches) apart to allow room for growth.
Water well after planting but avoid overwatering before shoots emerge to prevent rot.

Hardening Off

Before planting outdoors, harden off your young plants by gradually exposing them to outdoor conditions over 7-10 days.

Caring for Your Dahlias

Watering

Dahlias need a consistent supply of water, especially during dry spells.
Water deeply once or twice a week, aiming moisture at the roots rather than the foliage.
Drip irrigation or soaker hoses are ideal to keep foliage dry and reduce disease risk.

Feeding

Once plants reach about 20 cm (8 inches), feed fortnightly with a high-potash fertilizer (such as tomato feed) to encourage abundant flowering.
Incorporate slow-release fertilizer or organic amendments into the soil at planting.

Pinching and Staking

When dahlias are about 12 inches (30 cm) tall, pinch out the main growing tip just above the highest set of leaves. This encourages bushier growth and more flowers.
Tall varieties require staking or support to prevent flopping:
Use bamboo canes or sturdy stakes placed at planting time.
Tie stems loosely every couple of weeks as the plant grows.

Deadheading

Remove spent flowers regularly to encourage continuous blooming.
Identify spent blooms by their pointed shape (buds are round).
Cut the entire flowering stem back to a pair of leaves.

Common Dahlia Problems and How to Solve Them

Pests

Slugs and snails can damage young shoots—use organic slug bait or barriers.
Watch for aphids, earwigs, and caterpillars and treat with insecticidal soap or natural predators.
Red spider mites may appear in hot, dry conditions—regular watering and misting can help.

Diseases

Avoid overwatering to prevent tuber rot.
Powdery mildew can affect foliage—ensure good air circulation and avoid overhead watering.
Remove and destroy any infected plant parts promptly.

Overwintering Your Dahlias

In colder climates, dahlias do not survive frost and must be lifted after the first frost blackens foliage.
Cut stems back to about 12 cm (5 inches).
Gently lift tubers with a fork, brush off excess soil, and dry in a cool, dry place for 1-2 weeks.
Store tubers in a frost-free, dark location like a garage or shed in dry compost or sand.
Do not water during storage.
In mild climates, tubers can be left in the ground with a thick mulch of straw or mushroom compost for frost protection.

If you’re interested in other ways to extend your growing season, check out our DIY raised bed guide for tips on protecting and organizing your garden.

Growing Dahlias in Containers

Choose pots at least 30 cm (12 inches) wide and deep.
Use a high-quality potting mix enriched with organic matter.
Plant tubers at the same depth as in nursery pots.
Provide stakes or supports as needed.
Water and feed regularly, as container plants dry out faster.

For more container gardening inspiration, see our top 20 plants for pots and containers and our tips for growing tomatoes in containers.

Practical Tips for Beginner Gardeners

Plan your garden space carefully to accommodate the size of your chosen dahlia varieties.
Start with easier, smaller varieties if you’re new to dahlias.
Keep a garden journal to track planting dates, varieties, and care routines.
Use mulch to retain moisture and suppress weeds.
Share extra tubers with friends or neighbors to expand your dahlia collection.

If you’re looking to improve your overall gardening skills, our beginner’s guide to building a garden shed can help you organize your tools and supplies.

Conclusion

Growing dahlias is a rewarding experience that adds spectacular color and life to any garden. By choosing the right location, planting tubers correctly, providing consistent care, and protecting your plants from pests and frost, you can enjoy a stunning display of blooms from summer through fall. Whether in garden beds or containers, dahlias are a fantastic choice for beginner gardeners eager to cultivate beautiful flowers with relatively simple care.

Start your dahlia journey today and watch your garden flourish with these radiant blooms!

Why Grow Dahlias?