Here's Why You Should Pay Attention to the "Rules of Three" In Gardening

Designing a gorgeous, natural-looking garden or container can be as easy as 1, 2, 3 when you use the "rules of three" planting trick, also commonly used in interior design. By happenstance, there are several other important rules of three in gardening. Read on to learn all of them, and how to use them in your own garden.

What Is the "Rule of Three" for Planting?

When you're decorating your living space, the "rule of three" is a helpful design trick you can use to pull everything together for a balanced, cohesive look. You might group three of the same things, like pieces of art, or different items like a stack of books and two vases. The goal is something that feels layered and organic, rather than perfectly matched or styled. It works because our eyes are not only drawn to symmetrical arrangements, but also to asymmetrical groups and variations in patterns.

The gardening rule of three means planting in odd-numbered groups, so think in terms of 3 plants, 5 plants, 7 plants and so on.

How to Use the Planting "Rule of Three"

• Use the same kind of plants together: You'll make it easier for visiting pollinators like hummingbirds or bees to save their energy and flit around to collect nectar or pollen.
• Layer different heights, textures, colors and sizes: Nature does this all the time, so your garden design will seem casual and relaxed. Plus, growing different kinds of plants in a group may interrupt the spread of insect pests or diseases, if the pest or disease affects only one of the species. Try grouping a groundcover or low-growing hosta with a medium-tall coneflower or daisy and a taller ornamental grass or shrubby boxwood. Annuals, perennials and even vegetable plants can work, whether you grow them in the ground, a garden bed, or containers. Mingle textures with wind-blown grasses, large-leaved hydrangeas, broad elephant ears or fine-cut ferns.
• Play with planting shapes: You can use the rule of three design to plant in lines, triangle shapes, blocks or clusters, although odd-numbered groups usually look better in loose, unstructured arrangements. You can always repeat your groups of three (or 5 or another odd-number) throughout your garden area, if you want some repetition. Eventually, your plants may even spread enough to merge.
• Keep companion planting in mind: Companion planting is also part of the gardening rule of three. It refers to grouping plants that need the same basic amounts of sun, water and fertilizer together, so you don’t inadvertently drown your drought-tolerant yucca when you're growing it beside your thirsty Japanese iris.
• Get decor involved: Don’t want any plants at all? Use the rule of three to add rocks, sculptures or other hardscaping elements to your garden.

What Is the "Rule of Three" for Perennials?

There’s a handy saying to remember how perennials will grow: The first year they sleep (that is, they develop good roots), the next year they creep (they put out more foliage and flowers, but they grow slowly) and the third year they leap (they grow and bloom or fruit vigorously).

How to Use the Perennials "Rule of Three"

Write down the date when you plant your perennials, so you’ll know what to expect from them, and so you can plan to add annuals or other fast-growing plants to keep your garden colorful, lush and full when they slow down or stop. Remembering when you planted will also help you know when your perennials are mature enough to divide and replant.

What Is the "Rule of Three" for Nutrients?

Different plants need different kinds and amounts of nutrients, but nitrogen, potassium and phosphorus are three big essentials. Nitrogen (N) encourages leafy growth, phosphorus (P) helps promote strong roots, flowers and fruits and potassium (K) works to help plants resist disease and stay healthy. You’ll see them shown in this order, NPK, on fertilizer bags or boxes.

In general, give new plants a fertilizer with a higher middle number, P, to boost their roots. Flowers and fruits need higher amounts of the second and third elements, P and K. Leafy greens and lawns benefit from more nitrogen, N.

How to Use the Nutrients "Rule of Three"

Before you fertilize, check your soil with a home soil analysis test kit or send a sample to your local extension service and tell them what you want to grow, so you’ll know what to add, and in what amounts. Soil amended with plenty of good compost usually needs fewer additives.

What Is the "Rule of Three" for Temperatures?

Try to avoid working in your garden between the hours of 11 a.m. and 2 p.m. in the hot months. That’s when the sun’s UV rays are the most intense and temperatures are the highest. You don’t want to risk overheating or getting dehydrated or sunburned. If you must go out at those times, wear a hat and sunscreen, keep plenty of water handy and try to work in the shade.

How to Use the Temperatures "Rule of Three"

Your plants get stressed during these hours, too, as water evaporates from their roots, and their stomata (leaf pores) close. It’s better to pick your flowers or harvest your vegetables during the cooler hours, so the blooms last longer in vases and the veggies store better.