Proper plant spacing is an important key to garden success. Following the recommended plant spacing requirements allows plants to develop fully and properly fill the area. Proper spacing also prevents the invasion of weeds and allows enough air movement between plants to prevent diseases.
Recommended plant spacings are listed on the back of seed packages or on plant identification tags. Reference materials like books and trusted websites can also provide recommended spacing for your plants.
Find the Area | Determine Number of Plants | More Information
Start by Finding the Area of the Planting Bed
To determine the correct number of plants needed for a particular area it is necessary to know the area or square footage of the planting bed.
Area of Rectangular Bed
A simple rectangular bed is one of the most straightforward bed shapes to determine planting area. Simply, multiply its length by its width.
Area = length × width
Area of Triangular Bed
To determine the planting area of a triangular-shaped planting bed, Measure the length of the base and then the height (the distance from the top point down to the base). Then, use the formula below to determine square footage.
Area = base × height × 0.5
Area of Circular Bed
For a round planting bed, multiply pi (π=3.14) by the radius squared. The radius equals the distance from the center of the circle to the edge.
Area = 3.14 × radius2
Area of a Semicircle Bed
For a semicircle (also called a half-moon or half-circle) bed, start by finding the length of the radius. For a semicircle, the radius equals the length of the flat/straight edge divided by two. Then, use the formula for the area of a circle and multiply it by one-half.
Area = 3.14 × radius2 × 0.5
Area of Oval (Elliptical) Bed
An oval bed (more accurately referred to as an ellipse) can be found after collecting two measurements. Measure from the center of the bed to the furthest edge point. This is called the major radius. Then, going back to the center, at a right angle to the major radius, measure from the center to the bed edge - this is the minor radius. Multiply those two numbers with pi (π=3.14) to get the area.
Area = 3.14 × major radius × minor radius
Area of an Irregular-Shaped Bed
Many garden beds have a more irregular shape. For beds comprising straight lines, simply break the bed apart into triangles, rectangles, and/or semicircles. Find the area of each piece and add them together.
For more complex irregular shapes, such as a bed shaped like a kidney bean, the bed area can be estimated with decent accuracy by first gathering several measurements. Find the length of the longest line within the shape - this is the length line. Along this length line, measure perpendicular width lines (at a 90° angle) to the length line. The distance between the width lines (called the segment width) must be equal along the entire length. For example, you might measure the width of the bed every 3 feet along that length line. The segment widths can be any number as long as they are equal to each other. The more width lines you measure, the more precise your area calculation will be. To find the area, add all of the width line lengths together and multiply it by the segment width.
Area = (sum of all width lines) × segment width
Multiply the Area by Plants Needed per Square Foot
Once the total area has been determined, the chart below can be used to determine how many plants are needed for the planting bed.
Multiply the square footage of the planting bed by the plants needed per square foot to determine the number of plants needed.
When using plants with different spacing requirements in the same area, break the planting bed into smaller shapes - one for each plant species. Find the area of each plant grouping and determine plant numbers using the chart below.
| Recommended Spacing | Number of Plants per Square Foot |
|---|---|
| 4 inches | 9 |
| 5 inches | 5.76 |
| 6 inches | 4 |
| 8 inches | 2.25 |
| 10 inches | 1.44 |
| 12 inches (1 foot) | 1 |
| 14 inches | 0.74 |
| 15 inches | 0.64 |
| 16 inches | 0.56 |
| 18 inches (1.5 feet) | 0.44 |
| 20 inches | 0.36 |
| 24 inches (2 feet) | 0.25 |
| 30 inches (2.5 feet) | 0.16 |
| 36 inches (3 feet) | 0.11 |
| 42 inches (3.5 feet) | 0.08 |
| 48 inches (4 feet) | 0.06 |
Example: You are planting daylilies 15 inches apart in a 28-square-foot planting area. This space would require 18 plants to fill it in properly. (28 × 0.67 = 17.92; rounded to 18)
More Information
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- How to Plant Perennials
- How to Plant Bare Root Plants
- Tips for Shopping and Selecting Quality Plants
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