The new Piet Oudolf borders at RHS Wisley are a real lesson in planting design.
And whether you have a large space or just a small yard, there are ideas and plant combinations for home gardeners as well as professionals.
(Strictly speaking, the area is called the ‘Oudolf Landscape’ but I’m mainly calling them ‘borders’ here.)
The Oudolf Landscape is a hill stretching gently up from the magnificent glasshouses. As you approach, a notice will tell you that the planting is in Oudolf’s ‘signature mix of block and matrix planting.’
Visit RHS Wisley in Surrey to immerse yourself in the re-vamped Piet Oudolf borders.
This is often referred to as ‘naturalistic planting’.
It’s certainly a quick way of creating a brilliant border. I visited the Oudolf Landscape at RHS Wisley just six months after it was planted up from bare soil. And although there were gaps where the ornamental grasses have yet to mature, the borders looked stunning even in their first year. They will go on getting better as they fill out.
They replaced twenty-year old ‘naturalistic’ Oudolf borders – so what has changed in that time?
Lesson 1: What is Piet Oudolf’s naturalistic planting style?
Firstly, what is naturalistic planting?
It is described as an ‘artistically stylised version of natural habitats’. Noel Kingsbury and Piet Oudolf define it in their classic book on naturalistic planting in ‘Planting – A New Perspective’. (Please note: links to Amazon are affililate, see disclosure)
It means you combine plants that grow well naturally in your area. And then you plant them in patterns that reflect -somewhat – how they would grow in nature.
Choose plants that need similar conditions and are appropriate to the soil and climate. So they won’t need the kind of intensive gardening care – the individual pruning and fertilising of certain plants – that some traditional herbaceous borders need.
Naturalistic or natural?
Many keen gardeners say that seeing plants in the wild helps them understand how they behave in the garden.
If you’re thinking of doing naturalistic planting in your own garden, visit gardens that showcase the style. This includes RHS Wisley, Hauser & Wirth in Somerset and many public landscapes, such as the High Line in New York.
And also look at how plants grow in natural landscapes near you.
Often when a friend and I walk around the local marshes with their drifts of wild grasses, we say ‘it’s all looking very Piet Oudolf today.’
And my sister-in-law in Vermont has allowed her field to be taken over completely by wild New England asters (Symphyotrichum novae-angliae), Showy Goldenrod (Solidago speciosa) and Joe Pye Weed (Eupatorium). It looks very ‘Oudolf’!
Seeing this meadow was a revelation. In some places you could almost imagine it had been planted up.
Piet Oudolf borders with asters and hylotelephium at RHS Wisley (top) and a field of wild asters and eupatorium in Vermont (above). The Vermont field is completely wild – totally created by nature, while the Oudolf borders above it are deliberately designed and planted with a mix of ‘block planting and matrix planting’.
Naturalistic planting isn’t the same as re-wilding (see Discover the Magic of A Re-Wilded Garden).
And, although naturalistic planting, such as the Piet Oudolf Landscape at RHS Wisley, is very sustainable and wildlife-friendly, you can be sustainable and wildlife-friendly without necessarily restricting yourself to naturalistic planting.
But it is an effective and dramatic style of planting.
Lesson 2: What’s the difference between block planting and matrix planting?
To understand the principles behind naturalistic planting, think about block planting and matrix planting.
Piet Oudolf defines ‘block planting’ as a traditional planting concept. It is a big block of one kind of plant. He considers that there are advantages and disadvantages to block planting.
The main advantages are that it is easy to plant and maintain, which is why you often see big blocks of identical flowers in parks. Any weed will instantly be noticeable, which means that even non-experts can weed it out.
And any other treatment, such as cutting down or cutting back, can be done clump by clump, rather than plant by plant.
Hylotelephium (formerly Sedum) ‘Matrona’ in block planting in the Piet Oudolf borders at RHS Wisley. The block adds a big punch of colour, repeated elsewhere in the borders. And you can see the more informal ‘matrix planting’ weaving together the other plants.
Ian Trought, an RHS horticulturalist on the Oudolf Landscape, says that in a large landscape, block planting creates the necessary pops of colour. If you have a big space, you need big chunks of colour.
Block planting doesn’t work as well in smaller gardens though, he says. You’d have one big pop of colour for a few weeks, then not much to enjoy after that.
And Noel Kingsbury writes that block planting is also somewhat old-fashioned (think of those geometric blocks of bedding plants in municipal parks!)
Lesson 3: Oudolf borders – matrix planting is like a fruit cake…
‘There are a lot of different answers to the question ‘what is matrix planting’,’ says Noel Kingsbury in ‘Planting – A New Perspective’. However he and Piet Oudolf describes it as being ‘like a fruit cake’.
You plant an initial matrix of one plant repeated. This is often an ornamental grass, which is like the ‘cake mix’ of a fruit cake. For example, grasses such as Carex, Deschampsia cepitosa or smaller Molinias are often used as ‘matrix plants’. These establish a background, then you can thread other plants through them.
Ian Trought also describes it as a planting of ornamental grasses with perennials dotted in through them. The grasses will grow and spread to create a permanent background.
Then the colourful salvias, yarrow and asters are planted in groups amongst them. These create splashes of colour – like the fruit and nuts of a fruit cake, according to Kingsbury.
It’s not the only use of ornamental grasses in this border, however. Every so often a single grass, such as a Pennisetum or a Festuca, stands at the front of a border to break up colourful blocks of flowers.
Dense ‘matrix and block planting’ discourages weeds and has a natural-looking relaxed feel. As the borders grow and develop, different plants will dominate at different seasons.
Matrix planting also combines plants with similar or complementary needs. For example, shallow-rooted grasses and deeper rooted perennials can grow well together even when they’re densely planted because they’re not occupying exactly the same layer of soil.
So naturalistic planting is easier to look after, too. The ideal is to create a natural-looking border which is so full of plants you want that it excludes weeds.
So plant the grasses first
If you’re starting from scratch with naturalistic borders, then plant the grasses first.
And even if you’re not necessarily doing naturalistic planting, then the ‘grasses first’ philosophy works well. Paul Seaborne of Pelham Plants says that he always positions the individual ornamental grasses first in a border, then works the rest of the planting around it.
Lesson 4: new ideas for a slope from the Oudolf borders
The new Oudolf borders have one major design change which fundamentally alters the relationship of the visitor to the garden.
The borders of twenty years ago lined a wide, straight path, going up the hill. You could view the borders on either the side as you walked up the hill. And you could look down on them when you reached the top.
Piet Oudolf borders at Wisley from 2001-2024. This previous scheme had one central path going from the top to the bottom of the slope, with naturalistic borders on either side. Photos: Top by Neil Hepworth. Above by Adam Alexander. Photos reproduced by permission RHS.
Now there is a broad curving path snaking up the hill, going from one side to the other.
You are immersed in the border from both sides, with a different view every time you turn the corner. It’s also more wheelchair/wheelbarrow-friendly, as the slope is less steep when it zig-zags from side to side.
The curving zig-zag path is designed to slow you down and immerse you in the planting. There are benches on every level, so you can sit and enjoy the view down to the glasshouses.
And when you see people coming down the path, it looks as if they’re walking through the middle of the planting. Oudolf describes this as a way of slowing you down and allowing you enjoy the borders more.
If you’re thinking of steps or terracing for a sloping garden, consider whether this type of zig-zag path would be be easier to live with and offer more views of the garden.
Ian Trought says that you have to consider drainage on a slope. Not only does that mean the way you plant on a slope, but also how water flowing downhill may affect the paths. The previous wide grass path got too muddy with people tramping over it and rainwater going down hill. The new lateral paths have drainage built into them.
The Oudolf borders also showcase the value of a slope for showing off border plants. Because the traditional ‘big plants at the back, smaller ones at the front’ is not part of this type of design, a slope gives you a good view of the whole border.
See here for more design and planting ideas for gardening on a slope.
Each slope level has a friendly bench. You can pause to enjoy the planting stretching out below you.
Lesson 5: Repetition and contrast in Oudolf borders
These Oudolf borders are a lesson in repetition and contrast. The big blocks of colour are repeated across the landscape. All the individual flower and grass species are repeated all the way up the hill. There are 155 species of plant in all, which is not very much when you consider the size of the hill.
Then the contrast comes from the differences in the plant shapes, colour and structure.
Here you can see both repetition and contrast. The daisy flowers of Aster ‘New Jersey Skies’ contrasts with the rounded clumps of Hylotelephium ‘Matrona’. The naturalistic planting contrasts with the sharp edging of the path. And the spiky stems of Atlas Fescue grass contrast with thicker fleshy leaves of the hylotelephium.
There is more contrast between the way the plants are interweaved together, yet the path is sharply delineated with edging. Soft planting. Hard edged path. Spiky plant. Rounded plant.
It all works together to give your eye plenty to look at.
I don’t think this style of planting would work in very small gardens. You’d need a middle-sized or larger garden to create this effect. But I do think it’s worth thinking about what the structure or architecture of a plant contributes to a border in any size garden.
How can I create a small-scale version of Piet Oudolf’s style?
Ian says that you can repeat the same combinations of plants on a smaller scale. Use the same plants, but fewer of them.
Choose a background grass, then add some perennials into the planting. This means you won’t have gaps if some fail.
Some of the matrix plants in the Oudolf borders at RHS Wisley are quite delicate grasses, such as Prairie Dropseed (Sporobolus heterolepsis), Tufted Hair Grass (Deschampsia cespitosa) and Molinia ‘Poul Peterson.’
And Noel Kingsley & Piet Oudolf recommend that you think more about the structure and architecture of the plant than you do about its flowers.
Structure will give you long term impact. You won’t have to rely entirely on flower colour to make your border beautiful.
Contrast the architecture or structure of the planting. Here you can see how the rounded mounds of aster and solid blocks of hylotelephium contrast with the thin grassy spikes of Festuca.
And Ian also recommends ‘Planting – A New Perspective’ for plant choice because it has a chart at the back, listing the plants that Oudolf uses often, with their height, season of interest, the shape of their foliage, their structural interest and how many you plant per metre. ‘It’s like a recipe for planting.’
You don’t have to buy the biggest plants
He also says that you don’t have to spend lots of money on plants. ‘We planted the entire Oudolf Landscape with plants in 9cm pots, so you don’t have to buy the more expensive 2L pots. And if you do, you can often split them into two or more plants.’
The Oudolf borders at RHS Wisley are only around 6 months old. The 9cm plants have already filled most of the space. ‘Although we’ve been lucky that there’s been plenty of rain this summer,’ says Ian. There are just a few gaps, mainly the grasses matrix, but those gaps will be filled by the growing grasses by next summer.
The RHS Wisley Oudolf Landscape features hylotelephium (fomerly Sedum), echinacea, hardy geraniums, asters, heleniums, rudbeckia and stachys. These are all plants typically used in Oudolf borders. And they all work equally well in smaller gardens.
Achillea (yarrow) ‘Moonshine’ and Echinacea pallida ‘Hula Dancer’ with Aster ‘New Jersey Skies’ in the Piet Oudolf landscape at RHS Wisley. All these plants work well in smaller gardens. You can see the yarrow flower heads ‘going over’, but they are left until late February to benefit wildlife.
How do you maintain a Piet Oudolf inspired garden?
You won’t have to do the traditional border jobs of dead-heading, cutting back or replacing plants that have gone over with annuals. And there’s very little watering, too.
When plants go over in this naturalistic planting, their seedheads remain until they collapse. There are a lot of ornamental grasses in matrix planting. Most maintain their structure throughout winter. So instead of clearing away, you can enjoy the structural beauty of plants that are ‘over.’ ‘We leave the plants in these borders standing until late February,’ says Ian Trough.
These borders are ‘left standing’ until late February. By the time they are cleared away, they will have started to disintegrate, but they have offered shelter and seedheads to wildlife over winter.
However, naturalistic planting is not re-wilding and you do have some control. Weed out self-seeders (unless you want to keep them.) And most grasses need cutting down once a year in the spring.
Perennials, too, will need an annual clearing away, according to their various requirements. But, as Steve Edney and Lou Dowle point out in Brilliant Border Maintenance, leaving plants over winter often means there’s very little to clear away in spring. The collapsing vegetation will already have started to break down.
Naturalistic planting also focusses on plants that won’t need too much watering, too. Individual pampering of plants is out! Look at how to make a dry garden and 10 beautiful but tough perennials for suggestions of drought-resistant plants. And also see 15 drought tolerant plants that will also be happy if it rains.
When you choose your plants, make a note of their care requirements. Try to place plants that need similar care – such as cutting back – at the same time of year. So that makes maintaining the borders a much easier job.
What about wildlife and biodiversity in Piet Oudolf borders?
This naturalistic style is also good for nature. The plants are typically good for pollinators. And you leave the borders over winter, so you’re leaving the seedheads for the birds.
You use less fertiliser and you water less, so you’re using fewer resources.
The emphasis on big blocks of planting means that you create a high density of plants. Large borders with paths running through them have lots of plants per square metre. More plants is always good for wildlife and biodiversity.
See gardening for biodiversity here and a garden that looks gorgeous and supports wildlife for more about how you can support wildlife and biodiversity, regardless of your garden style.