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Units

Zinnia Spacing Calculator

How far apart to plant zinnias, and how many fit your bed, row or area.

Units
In the row
9 to 12 in
In a bed, each way
9 to 12 in
in

Published for Zinnia: 9 to 12 in.

Where you plant
Pattern
ft
ft
More optionsEdge margin
Space at the edge

Half a spacing keeps each plant inside the bed, so neighbours in the next bed are still a full spacing away. Plant on the edge when the plants may spread past it, such as the first and last post of a hedge line.

Zinnias that fit

36plants

About 1.31 per sq ft of ground.

Triangular (staggered) spacing would fit 43 here.

Top view, 8 × 4 ft. Each circle is the space one plant gets.
Plants per sq ft
1.31
Plants per acre
56,894
Plants per hectare
140,589
Ground per plant
0.77sq ft
Ground covered
32sq ft

Common raised beds at this spacing

BedAt 10.5 in, square
4 x 4 ft16
4 x 8 ft36
3 x 6 ft18
4 x 12 ft52

How these numbers are worked out

In a square pattern the rows are one spacing apart, so each plant takes spacing × spacing of ground.

10.5 in × 10.5 in = 0.7656 sq ft per plant

43,560 sq ft per acre ÷ 0.7656 sq ft = 56,895 plants per acre

Per-area figures ignore the edges. The count for a bed, row or circle places each one, so it is usually a little lower. One acre is 43,560 sq ft; one hectare is 10,000 m².

Growing in pots? .

How far apart to plant zinnias

Utah State University Extension's zinnia cut flower guide grows zinnias on a 9 by 9 inch or a 12 by 12 inch grid: 9 inches for the smaller types such as Zinderella, Queen and Mexican zinnias, and 12 inches for large cut-flower types such as Benary's Giant, California and dahlia-flowered zinnias.

The calculator starts at 10.5 inches each way, the middle of that range. Pick "Smaller types" or "Large types" in the variety menu to switch to 9 or 12 inches.

How many zinnias fit a bed

BedSmall types, 9 inDefault, 10.5 inLarge types, 12 in
4 × 4 ft251616
4 × 8 ft503632
3 × 6 ft321818
4 × 12 ft805248

Each count keeps half a spacing clear along the bed edges, the way the calculator counts. In a 4 ft wide bed, 9 inches gives five rows across and 10.5 or 12 inches gives four, which is why the small types fit so many more. Along a fence or path, a 25 ft row takes 33 small or 25 large zinnias.

Small or large zinnias?

  • Small types (Zinderella, Queen, Mexican) take the 9 inch grid, so a 4 × 8 ft bed holds 50 plants.
  • Large types (Benary's Giant, California, dahlia-flowered) need the 12 inch grid, 32 plants in the same bed. Utah State reserves the wider spacing for them.

NC State's plant toolbox lists common zinnias from 6 inches to 3 feet tall and 8 to 12 inches wide, and notes they are prone to powdery mildew, leaf spots and other fungal problems. Good air circulation, full sun and good drainage help prevent fungal leaf diseases, so resist planting closer than the grid for your type.

Seeds, depth and timing

Utah State sows 1 to 2 seeds per cell or hole. Zinnias are frost sensitive: start seeds indoors 4 weeks before the last frost, or sow directly in the garden once the last frost has passed, as NC State also advises. At a soil temperature of 80 to 85 °F they sprout in 3 to 5 days. Your own dates by ZIP code are on when to start zinnia seeds.

If both seeds in a spot come up, keep the stronger one so each grid point holds a single plant.

Using the calculator

Choose a bed, a row or an area. Square spaces plants evenly both ways, which matches Utah State's grid; Triangular (staggered) offsets every second row and fits a few more plants on large areas. Switch to centimetres with the unit toggle: 9 inches is about 23 cm and 12 inches about 30 cm.

To work out seed packets for a large cutting garden, use the seed calculator. To grow zinnias beside vegetables, lay out the bed in the raised bed planner.