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Dahlia Plant Spacing Calculator
Dahlia spp.
Start with the source-backed 12-inch spacing default, then enter your bed length and width to calculate an approximate plant count, seeds or starts needed, and the spacing used. Defaults are editable so your variety and growing system can take priority.
Quick spacing answer
How far apart should you plant dahlia?
Start with 12 inches between plants using a two rows per bed layout. The source-backed range in this dataset is 12–18 inches.
At a glance
- Recommended spacing
- 12″
- Supported range 12–18″
- Planting pattern
- Two rows per bed
- Time to first production
- Varies by variety
- Enter your supplier's maturity value to estimate
- Succession planting
- Not typical
- Start indoors
- Direct sow / not typical
- Production pattern
- Cut-and-come-again
- Pinch
How many dahlia plants do I need?
Enter your bed length and width below. The shared calculator is prefilled with Dahlia's sourced spacing and shows the approximate plant count, spacing used, and seeds, starts, or planting material to prepare where appropriate.
Your plan
- Spacing used
- 12″
- Tubers to buy (10% buffer)
- 111
Dahlia is typically grown from tubers, not seed trays, so tray counts are hidden.
Dahlia spacing chart
These values come from the existing crop record. The density column is derived planning math and does not add a new horticultural recommendation.
| Context | Spacing | Geometric plants/sq ft |
|---|---|---|
| Dataset default | 12″ | 1.00 |
| Source-supported range | 12–18″ | Varies with selected spacing |
Plants per square foot is transparent square-grid planning math (144 ÷ spacing²), not an extension-service recommendation or a guarantee of field performance.
Dahlia in raised beds
Enter the raised bed's actual length and width in the calculator. It applies the selected spacing and two rows per bed model to estimate how many planting positions fit; it does not assume a crop-specific raised-bed recommendation that is absent from the source data.
Dahlia per square foot
At 12″ spacing, square-grid geometry equals approximately 1.00 plants per square foot. This is a geometric planning estimate based on the displayed spacing—not an agronomic guarantee. The calculator may use a different documented model for two rows per bed layouts.
Why dahlia spacing changes
Variety, production system, support, and planting layout can change usable spacing. Plantometry keeps the sourced default editable and shows a range only when the crop record supports one.
How many dahlia plants fit in my bed?
Use the calculator above with your bed dimensions. The result shows the approximate plant count, the spacing used, and seeds or planting material to prepare where appropriate.
More Dahlia planning
Planning notes
- Corralling
- Pinching
Cut-and-come-again. A planting keeps producing new stems over a relatively long harvest period when it is picked regularly, so successive plantings are usually spaced farther apart.
- Pinching is commonly used in this production system.
- Corralling for structural support is commonly used.
- First-production timing varies by cultivar and growing system, so enter the maturity value from your seed supplier to estimate production.