Dahlia Spacing: How Far Apart to Plant Dahlias for Healthy Growth and Stunning Blooms

Introduction

When planting dahlias, it’s tempting to fit in as many tubers as possible to maximise colour. But resist the urge! Getting the spacing right is one of the most important factors in growing strong, healthy, and flower-packed dahlias.

Spacing impacts airflow, disease prevention, root development, and ease of maintenance — and if you plant too closely, you’ll risk overcrowding, reduced flowering, and leggy growth.

In this complete guide, you’ll learn exactly how far apart to plant dahlias, whether you’re growing in beds, borders, containers, or allotments in the UK.

Quick Answer: How Far Apart to Plant Dahlias?

Spacing depends on mature size, habit, and purpose (display vs. cutting).

Why Dahlia Spacing Matters

Correct spacing:

✅ Promotes stronger, bushier growth
✅ Allows airflow between plants, preventing powdery mildew and fungal issues
✅ Gives roots and tubers space to expand
✅ Makes it easier to weed, feed, water, and stake
✅ Prevents flowers and stems from competing for light

Poor spacing leads to crowded, leggy plants, fewer blooms, and greater risk of disease.

Factors That Affect Dahlia Spacing

1. Dahlia Variety

Different types grow to different widths and heights. Spacing should reflect this.

2. Purpose: Display vs. Cutting

• Display beds: Wider spacing = more impressive individual plants
• Cutting gardens: Slightly closer spacing boosts yield per square metre

3. Growing Method

4. Height and Support Needs

• Taller varieties need more room to allow for staking
• Wider spacing prevents staked dahlias from shading others

Dahlia Spacing by Plant Size

🌱 Dwarf and Bedding Dahlias

• Spacing: 20–30 cm (8–12 inches)
• Ideal for: Edges, containers, and front of borders
• Compact habit — don’t need much room to flourish

🌸 Medium-Height Dahlias

• Spacing: 40–50 cm (16–20 inches)
• Ideal for: Mixed borders, informal garden displays
• Allow enough space for airflow and access

🌺 Large and Dinner Plate Dahlias

• Spacing: 60–75 cm (24–30 inches)
• Ideal for: Centre of borders, standalone specimens, or cutting beds
• Big blooms need room to show off!

How to Measure and Mark Dahlia Spacing

1. Use a measuring tape or long stick marked with increments
2. For rows, use garden twine stretched between two stakes
3. Use a dibber or trowel to mark each planting spot
4. Consider spacing in a triangle layout for better density and airflow in beds

💡 Tip: Stick plant labels in first to visualise layout before digging.

What Happens If You Plant Dahlias Too Close?

🚫 Reduced airflow = increased risk of mildew
🚫 Stems grow tall and leggy, searching for light
🚫 Fewer flowers due to overcrowding
🚫 Difficult to weed, feed, or stake plants properly
🚫 More likely to flop or snap in wind or rain

Dahlia Spacing for Cutting Gardens

If you’re growing for cut flowers:

• Plant closer: 30–45 cm apart
• Space rows 60 cm apart to allow walking and access
• Stake plants individually or with a netting grid for upright stems
• Prioritise yield and accessibility over display

Grow in blocks by colour or type for easier harvesting.

Dahlia Spacing in Containers

• Use one tuber per 30–40 cm pot
• For very large pots (50–60 cm), two medium dahlias max
• Too many in one container = poor airflow, low blooming
• Add grit for drainage and slow-release fertiliser

Great option for patios, balconies, and small gardens.

Companion Planting Considerations

✅ Give all plants space — don’t overcrowd with neighbours
✅ Use low-growing, non-invasive companions like:

Avoid planting too close to large shrubs or fast-growing annuals.

Tips for Optimising Dahlia Layout

🪻 Borders

• Place tallest dahlias at the back
• Gradually reduce height towards the front
• Space to allow light to reach all plants

🌿 Beds

• Space for a grid pattern layout — easier to water and maintain
• Add paths or stepping access if planting a dense bed

🌱 Allotments

• Plant in long rows for easy harvesting
• Mulch between rows to suppress weeds

Conclusion

Proper spacing is the foundation for healthy, productive, and show-stopping dahlias. By giving each plant the room it needs, you’ll enjoy bigger blooms, better airflow, easier care, and a stronger garden overall.

Whether you’re growing for display or cutting, in borders or allotments, following spacing guidelines tailored to your variety will ensure your dahlias reach their full floral potential.

Top 10 FAQs About Dahlia Spacing

1. How far apart should I plant dahlias in the ground?

Between 30 and 75 cm, depending on variety and size.

2. Can I plant dahlias close together for more flowers?

Yes — in cutting gardens, but maintain airflow and stake well.

3. What happens if I plant dahlias too close?

You risk mildew, fewer blooms, and flopping stems.

4. What’s the best spacing for dwarf dahlias?

20–30 cm apart is perfect for compact varieties.

5. How far apart should I space dinner plate dahlias?

Give them at least 60–75 cm — they’re big and need support.

6. What spacing should I use for dahlias in rows?

30–45 cm between plants, 60 cm between rows is ideal.

7. Can I grow multiple dahlias in one pot?

Only in large pots (50–60 cm) — limit to 1–2 tubers max.

8. How do I know if I spaced my dahlias correctly?

If you can walk between plants without brushing them, you’re on track.

9. Do taller dahlias need more space?

Yes — taller varieties need more room for light and staking.

10. What’s the best layout for a dahlia cutting patch?

Use tight spacing (30–40 cm) in rows, with paths for access and harvest.