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Dahlias Spacing For Healthy Growth: Ultimate Planting Guide

Did you know Dahlias can grow well over five feet, requiring significant ground spacing to span horizontally?

Growing Dahlias in a garden requires one to three feet of spacing to receive sufficient sunlight, air circulation, and nutrients. Potted Dahlias are better grown with one plant per pot to avoid crowding.

When grown in the right conditions, these bloomers will quickly increase and burst into colorful flowers.

Read to find out how much space to allow between different Dahlia varieties.

Can You Plant Dahlias Too Close Together?

Dahlias are abundantly flowering plants that begin blooming within 12-16 weeks of planting and grow about 12-24 inches each growing season.

Therefore, you should be wary about spacing these bloomers to ensure the bushes get sunlight and air circulation for healthy blooming.

Although not recommended, you can plant Dahlias close together if necessary, but yields may differ as the plants will compete for resources.

dahlias' tubers spacing
Place dahlia tubers individually or separately rather than in groups to allow for proper spacing and individual growth.

A large Dahlia can reach four to six feet in height, while medium-low Dahlias will reach about 3-foot tall, and dwarf varieties will hardly reach a foot.

Here is an overview of the plant’s sizes, growth, and flower production.

Miniature Dahlia1 to 2 feet (30-60 cm)
Pompon Dahlia1 to 3 feet (30-90 cm)
Medium Dahlia3 to 4 feet (90-120 cm)
Large Dahlia4 to 6 feet (120-180 cm)
Flowers Per Bush
(Single Season)
- Large variety has 10-20 blooms per plant
- Smaller variety has 12 or more blooms per plant
Growth Per Year1-2 feet (30-60 cm)
Max. Tuber SizeCorrelates to the plant's height

Hence, grouping Dahlia tubers together, especially when growing in a container, may be harmful. The plant will hardly reach the optimal height, and most tubers will fail to reproduce due to dwindling resources.

As for the depth of planting Dahlia tubers, the general guideline is to place them about 4-6 inches (10-15 cm) deep into the ground.

In colder climates (USDA 8 or below), planting the Dahlias slightly deeper, around 6-8 inches (15-20 cm), will protect the tubers from frost.

How Much Spacing To Keep for Planting Dahlia?

It may be more than essential to provide adequate spacing between two Dahlias for proper growth, airflow, and access to sunlight.

Generally, you should keep at least 1 foot and up to 3 feet distance between the two Dahlia plants.

However, the recommended Dahlia spacing in rows can vary depending on the variety and size at maturity.

Common varieties (Miss Rose Fletcher and Jersey’s Beauty) are often planted 12-18 inches apart. But standard varieties (Bishop of Llandaff, Kidd’s Climax, and Bonne Esperance) are usually planted 2 feet apart.

dahlia tuber growth
Growers Tip: For overgrown Dahlia tuber peeking out of the ground, add more soil over it to cover it.

You can plant a tuber within a foot for a compact bush and small flowers.

Follow this guideline to plant your Dahlias.

Plantation and Spacing

  • Before planting, refer to the specific variety’s information to determine its expected maturity size to estimate the required spacing.
  • Arrange the marked spots to provide enough spaces between Dahlia plants in all directions, depending on the variety you wish to grow.
  • Dahlias are cold-sensitive, so avoid planting tubers until the soil temperature reaches above 60°F (15°C).
  • Dig individual planting holes for each Dahlia tuber, ensuring each hole is wide enough for the tuber.
  • Place each tuber in the hole with the ‘eye’ (growing point) facing upwards.
  • The top of the tuber sits about 2-3 inches below the soil surface. Remember not to break or cut individual Dahlia tubers.
  • Cover the Dahlia tuber with 2 to 3 inches of soil to support stem growth.
  • Amend the soil bed with 2-4 inches (5-10 cm) of high-quality compost or well-rotted manure, such as bone meal or organic fertilizer.

Aftercare For Dahlias

  • Do not water the tubers right away. Instead, wait for it to sprout young green stems.
  • Once the stem reaches a foot tall, hard pinch by snipping out 3-4 inches (7-10 cm) of the growing center to encourage dense branching for increased flower production.
  • It may be a good idea to provide staking to tall varieties by mid-summer to check the plant’s growing structure.
  • If they appear crowded or begin to encroach on neighboring plants, consider thinning the bushes to maintain the desired spacing and air circulation.
  • Use liquid fertilizer such as 3-5-3 or 2-4-4 every 3-4 weeks throughout spring and summer.

When growing Dahlias in a container, use a 12×12-inch container and insert only one plant to ensure sufficient Dahlia spacing in pots.

Use a soilless mix and co-polymer moisture-retaining crystals. Change the soil every year if the roots start crowding.

From Editorial Team

The more you cut Dahlias, the better they bloom!

Therefore, harvest the flowers when they are in full bloom to make way for new flower buds and collect seeds.

Remember to cut back in autumn and leave the tubers in the ground, covered with several inches of dry mulch throughout winter. Or dig up tubers to store indoors instead.