Short answer
The 70/30 rule in gardening is a rough planting guideline: about 70 percent of a bed is made up of reliable “structure” plants that look good for most of the year, and about 30 percent is made up of seasonal or experimental plants that provide short-lived colour and change. It is a rule of thumb, not a law, and the name is used for more than one idea.
Where the 70/30 rule comes from
Country Living attributes the method to the garden designer Piet Oudolf. In that telling, roughly 70 percent of plants provide structure, meaning clear visual interest through autumn if not longer. The other 30 percent are “fillers” that contribute colour from flowers or foliage until midsummer, when they may look untidy or fade.
Designers have since broadened it. The common modern version is to build a bed around dependable, long-performing plants, then add seasonal accents on top. Our guide to landscaping with ornamental grasses applies the same thinking. One designer quoted by Country Living describes it as striking a balance between structure and spontaneity.
Other things people mean by 70/30
Because the rule is informal, you may see it used in other ways:
- Perennials vs. annuals: about 70 percent perennials, shrubs and trees (which come back every year) and 30 percent annuals or experimental plants. This also helps with budgeting, since only the smaller share needs replacing each season.
- Native vs. non-native: about 70 percent native plants and 30 percent non-native.
- Other uses: the same numbers sometimes show up in lawn, vegetable or planting-time advice.
If you read a gardening article that mentions 70/30, check which of these it means.
How to choose your 70 percent
These are the backbone plants, so choose them carefully.
- Start with the site. Check light, soil and water. Plants that suit your conditions will outperform ones that need constant care.
- Look for multi-season interest. Think about shape, structure and foliage as well as flowers. See year-round ornamental grasses for four-season interest.
- Consider mature size. Some plants look good young and become woody or scraggly with age.
- Use grasses and sedges. Ornamental grasses are classic structure plants because they keep their form into winter. Designers quoted by Country Living cite pink muhly grass and American beach grass among their favourites for this role.
How to choose your 30 percent
This is where you can experiment: annuals, short-lived perennials, bold colours or a theme that changes each year. Country Living’s experts suggest starting with natives that are easy to grow and good for pollinators, such as purple coneflower, black-eyed Susan, bee balm, milkweed and yarrow (see perennials to plant with ornamental grasses), and sticking to a theme for each season to keep the bed cohesive. Because these plants are expected to look rough for part of the year, the rule gives you permission for some of the bed to be less than perfect.
Whatever you pick, layer by height (low plants near paths and tall ones behind) and repeat colours, textures or forms so the eye can move through the bed.
Applying the rule in a wet or rain garden bed
The same idea works in a soggy or rain garden planting, as long as the plants suit the wet conditions. For the 70 percent, think of reliable water-tolerant grasses and sedges such as switchgrass, tussock sedge and palm sedge, which hold their shape through winter. For the 30 percent, use seasonal flowers that enjoy damp soil, such as cardinal flower, swamp milkweed or turtlehead (all mentioned by The Plant Native as wet-zone plants).
For plant lists by wetness, see ornamental grasses for wet areas and soggy soil and best grasses for rain gardens.
Does the rule have to be exact?
No. Treat 70/30 as a prompt to ask whether your bed has a solid foundation and enough room for change, rather than counting plants. Beds that are heavy on short-lived colour can look patchy by late summer, while those with only structure plants can feel flat. Adjust the ratio to your site and how much maintenance you want to do.