The Simple Rule of Three Makes Gardening Easier and Gardens More Interesting
In the world of garden design, the “Rule of Three” is a foundational principle that enhances visual interest and balance. By planting in odd numbers—especially in groups of three—you can create more visual pleasing plant arrangements.
Quite simply, using plants in groups of three, five, or seven looks better than symmetrical, even-numbered groupings. This technique works well in beds, borders, and containers, and is easy for both beginner and experienced gardeners to apply.
Odd-numbered groupings, particularly trios, create focal points and draw the eye in a dynamic way. Below, we explore five popular plants that are especially effective when used in groups of three. We have also included growing tips and reasons to love these plants!
Coneflowers (Echinacea purpurea) and the Rule of Three in Gardening
USDA Zones: 3–9
Mature Size: 2–4 feet tall, 1–2 feet wide.
Light Needs: Full sun
Soil: Well-drained, moderately rich.
Ease of Growth: Very easy; drought-tolerant once established.
Coneflowers are classic prairie perennials known for their large, daisy-like flowers with raised central cones. Planting three coneflowers together in a triangle pattern enhances their bold, daisy-like blooms and provides structure to perennial beds.
The beautiful flowers attract bees, butterflies, and birds, and bloom from early summer into fall. Their long-lasting blooms also make excellent cut flowers.
Ornamental Grasses (Pennisetum alopecuroides, Miscanthus sinensis)
USDA Zones: 5–9 (varies slightly by species)
Mature Size: 2–6 feet tall and wide.
Light Needs: Full sun
Soil: Well-drained, adaptable to poor soils.
Ease of Growth: Low-maintenance; drought-tolerant
These grasses offer movement, texture, and seasonal interest. Their arching blades and feathery plumes sway beautifully in the breeze. Grouping them in threes provides a soft, natural look that’s great for borders or as a backdrop to flowering plants.
Lavender (Lavandula angustifolia)
USDA Zones: 5–9
Mature Size: 1–3 feet tall and wide.
Light Needs: Full sun
Soil: Well-drained, slightly alkaline, sandy or loamy.
Ease of Growth: Easy if soil drains well; dislikes wet roots.
Lavender’s fragrant purple flowers and silvery foliage bring sensory delight. It’s a pollinator magnet, resists deer and rabbits, and is widely used in herbal and ornamental gardens.
When planted using the rule of three in gardening, lavender often forms a fragrant mound. Lavender is also perfect for edging paths or framing other plantings.
Hostas and the Rule of Three in Gardening
USDA Zones: 3–9
Mature Size: Varies greatly (6 inches to 3 feet tall and wide depending on variety).
Light Needs: Partial to full shade.
Soil: Moist, rich, well-drained.
Ease of Growth: Very easy; shade-tolerant.
Hostas are treasured for their bold foliage in a range of colors, from deep green to blue to variegated patterns. They are great for filling shaded areas and look lush and full when planted in trios. Some varieties also produce delicate flowers that attract hummingbirds.
Boxwoods (Buxus sempervirens)
USDA Zones: 5–9.
Mature Size: 2–6 feet tall and wide (depending on variety and pruning).
Light Needs: Full sun to part shade.
Soil: Well-drained, fertile soil.
Ease of Growth: Moderate; regular pruning improves appearance.
Boxwoods are evergreen shrubs used widely in formal and informal gardens. Their dense foliage can be pruned into neat shapes, making them perfect for structure and year-round greenery. When planted using the rule of three in gardening, boxwoods create elegant groupings in containers, entryways, or along pathways.
Final Thoughts on the Rule of Three in Gardening as a Design Element
Using the Rule of Three in your garden doesn’t require advanced design skills. But it does encourage a thoughtful approach to grouping and spacing. Plants like coneflowers, ornamental grasses, lavender, hostas, and boxwoods, you gain beauty and variety and also reliability and structure.
These plants are versatile, easy to care for, and visually striking when arranged in trios. That’s why they are ideal for gardeners who want simple design with maximum impact.
Keep in mind that the rule of threes in gardening can work with many different kinds of plants!
Here’s another great story you might enjoy:
How to Plant an Apple Tree
Planting an apple tree involves a combination of art and science. It begins with understanding your local conditions and ends with ongoing tree care. In this story, we will provide step-by-step instructions and photos showing the mechanics of how to plant an apple tree. Container-grown trees can be planted in the spring or fall. Bare root trees can be planted in the spring or fall when the trees are dormant.
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