Plant Slots
160
Stones
168
Soil
17 ft³
Area
40 ft²
Typical: 4–8 ft
Typical: 2–4 ft
Plant Slots
160
6 ft diameter spiral
Stones
168
Soil
17
ft³
Area
40
ft²
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Inputs
Result
Slant height = sqrt(9+9) = 4.24. Area = pi × 3 × 4.24 = 40 ft². Plant slots at 6" spacing = 40/0.5 ≈ 80 (varies by calculation).
Inputs
Result
Slant height = sqrt(4+4) = 2.83. Area = pi × 2 × 2.83 = 17.8 ft². Soil = 0.6 × 1/3 × pi × 4 × 2 = 5.0 × 0.6 = 3.0 ft³.
A standard herb spiral is 5–6 ft in diameter and 3 ft tall at the center. This size fits 20–30 herbs in microclimates from hot/dry at the top to cool/moist at the base. A 4 ft diameter works for small spaces but holds only 10–15 plants.
A 6 ft diameter, 3 ft tall herb spiral with 6-inch stones needs approximately 200–400 stones depending on stone size and wall thickness. Flat fieldstone or broken concrete work well. Budget about 1 ton of stone for a standard 6 ft spiral.
Top (hot/dry): Mediterranean herbs like rosemary, thyme, oregano, and lavender. Middle: sage, cilantro, parsley, and chives. Bottom (cool/moist): mint, lemon balm, and chamomile. The spiral creates microclimates matching each herb's native conditions.
A 6 ft diameter, 3 ft tall herb spiral needs about 10–15 cu ft of soil mix (roughly 5–7 bags of potting soil). Use a 50/50 mix of compost and garden soil. Add gravel at the base for drainage, especially in clay soil areas.
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Last Updated: Mar 19, 2026
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