Growing Dahlias: A Botanical & Practical Guide for Gardeners and Cut Flower Growers

Few flowers inspire the kind of devotion that dahlias do. These late-summer showstoppers reach their peak just as much of the garden begins to fade—and somehow manage to look even better for it. Add in their extraordinary diversity of form and color, plus the fact that they’re surprisingly easy to grow, and it’s no wonder dahlias have become indispensable in both home gardens and professional cutting fields.

This guide breaks dahlias down into clear types, explains how and when to grow them, and shares real-world strategies for short growing seasons, container growing, and maximizing blooms—especially if you’re growing for cutting.

By midsummer, your garden (and your kitchen table) can be overflowing with flowers that are rarely available outside florist-only markets—and often cost a small fortune per stem.

Why Grow Dahlias for Cutting?

Dahlias are one of the most coveted cut flowers in professional floral design. Many specialty varieties are only available through wholesale growers, and even then, they command premium prices.

When you grow your own, you gain:

• Access to hundreds of varieties unavailable at retail

• Stems cut at peak freshness

• Blooms that last longer in the vase

• The freedom to harvest generously and often

With minimal planning, you can be harvesting dahlias in 90–120 days, depending on bloom size.

Understanding Dahlia Timing (Especially in Short Seasons)

Dahlias are tender perennials grown as annuals in most climates.

• Days to bloom: 90–120 days

• Larger blooms = longer time to flower

• Frost sensitive (both spring and fall)

Here in Colorado, we average ~140 frost-free days, which means large “dinner plate” dahlias often just begin blooming before fall frost arrives.

The Solution: Pre-Sprouting & Container Growing

To stay ahead of the season:

• Start tubers in pots early

• Grow some (or all) dahlias in containers

• Move plants indoors or into a greenhouse when frost threatens

This approach dramatically extends harvest windows—sometimes by weeks.

Types of Dahlias (and Which Are Best for Cutting)

Dahlias are classified by flower form and size, not plant height alone. For cut flowers, stem length and bloom durability matter most.

🌸 Pompon & Ball Dahlias (Best for Cutting)

• Bloom size: 2–4"

• Form: Perfectly round, tightly packed petals

• Why growers love them:

  • Long, strong stems

  • Excellent vase life

  • Extremely productive

These are workhorses in bouquets and event work.Color often deepens or shifts as blooms age—adding visual interest.

🌼 Mid-Size Decorative Dahlias (Most Versatile)

• Bloom size: 5–8"

• Largest color range

• Includes solid colors, bicolors, streaked, and painterly varieties

These are ideal for:

• Mixed bouquets

• Market bunches

• Focal flowers without overwhelming arrangements

  
  

🌺 Dinner Plate Dahlias (Statement Flowers)

• Bloom size: 8–12"+

• Dramatic, romantic, and unforgettable

Favorites like Labyrinth and Café au Lait shine as focal blooms—but require:

• Longer seasons

• Strong support

• Early starts

Worth it? Absolutely—especially if you start them in pots.

🌱 Border & Carpet Dahlias (Primarily Landscape)

• Shorter stems

• Excellent garden plants

• Limited use as cut flowers

  
  

Where to Buy Dahlia Tubers

Reputable suppliers matter—healthy tubers equal healthy plants.

Highly recommended sources:

• Swan Island Dahlias – legendary selection, sells out earlyhttps://www.dahlias.com

• Arrow Head Dahlias – Colorado-grown and climate-adapted

• Breck’shttps://www.brecks.com

• Eden Brothershttps://www.edenbrothers.com

💡 Tip: Order early—many varieties sell out by late winter.

How to Grow Dahlias: Step-by-Step

1. Pre-Sprouting Tubers Indoors (Highly Recommended)

When your tubers arrive:

• Use a pot with drainage holes

• Fill with fresh potting mix

• Lay tuber horizontally, lightly covered

  
  

Critical rule:👉 Do not water heavily.Dahlias rot easily before growth begins.

Ideal conditions:

• Temperature above 60°F

• Bright room, indirect light

• Optional: light misting only

  
  

Once green shoots appear, roots have formed and regular watering can begin.

2. Hardening Off

When outdoor temps are consistently above 60°F:

• Move plants outside for a few hours a day

• Increase exposure over 3–4 days

• Protect from wind and direct sun initially

  
  

3. Planting: Ground vs Containers vs Grow Bags

All methods work—choose based on space and flexibility.

In-ground

• Traditional and productive

• Requires lifting tubers in fall

Containers

• Easier frost protection

• Ideal for patios and small gardens

• Minimum size: 12–15 gallons

Grow bags

• Excellent drainage

• Easy to move

• Simplifies fall tuber lifting

For dahlias, 15-gallon grow bags work beautifully.

4. Support Early (Before It’s Needed)

Dahlias get heavy fast.

• Install tomato cages or stakes at planting

• Prevents breakage and wind damage

• Becomes invisible once plants fill in

  
  

5. Pinching for More Blooms

When plants reach ~8" tall:

• Cut back to ~4"

• Cut just above a leaf node

This encourages:

• Branching

• More stems

• Stronger plants

• Double the blooms

Yes, it’s hard—but it works.

Harvesting & What Comes Next

Once blooming begins:

• Cut often to encourage more flowers

• Harvest in early morning or evening

• Condition stems in cool water immediately

In fall:

• Lift tubers after frost

• Store and divide for next year

👉 See our follow-up post on overwintering and splitting dahlias to double your stock annually.

Additional Trusted Resources

• American Dahlia Society: https://www.dahlia.org

• Floret Flower Farm Dahlia Guides: https://www.floretflowers.com