Dutch master: the garden design genius of Piet Oudolf The High Line in New York has become a firm tourist favourite A developing style Cut to 2010 and the planting on the High Line, the raised linear park on the lower west side of New York. The character is startlingly different, to such an extent that it seems almost like the work of a different hand. Here, the planting is intermingled, less obviously painterly, and much more like a miraculous slice of nature than an artful arrangement of plants. To heighten the quality of nature in the city, the composition is almost entirely of American natives, planted in ecological groupings and associations that create an arresting contrast to the smart steel and concrete detailing of the park and the urban grit that surrounds you. The volume of grass is up, the flowers down, and the content and spatial character is constantly shifting like a linear narrative as you walk by. There are woodland bits, open bits and everything in between. A new book entitled Planting: A New Perspective (see below), written by Noel Kingsbury, but prepared in collaboration with Oudolf, charts the progression of his work between these two extremes of style and rightly places him as the pivotal planting designer of the last quarter century. The most riveting part of the book shows planting plans varying from the Pensthorpe type of project of blocky planting, which seemed so naturalistic at the time, to the more recent work such as the High Line, characterised by much greater interweaving of plants and a close mimicry of plant associations and patterns found in nature. Oudolf's early work was a great influence throughout the temperate world because it was bold and delicate at the same time. He looked at the way plants behaved throughout their growth cycle and was as interested in how they looked when they were dying as much as when they were in flower. This in itself is as revolutionary as it gets in the world of planting design, but it is perhaps fair to say that the style was more painterly than it was ecologically inspired. Over the past 10 years this has changed, and while much of this has to do with his regular trips to see plants in the wild, particularly in the US and eastern Europe, Oudolf would highlight the influence of several key practitioners working in the intermingled style. Perhaps foremost among these would be Cassian Schmidt, the curator of the garden at Hermanshoff in Weinheim, Germany. In this remarkable garden near Frankfurt, Schmidt has developed a number of plantings based on a repetitive grid of plants where each species in the grid is selected as much for the ecological niche it fulfils as much as for its decorative impact. This type of "matrix" planting is now the rage in Europe and, as with many things systematic, Germany is at the forefront of developments. It is now possible to purchase a perennial plant mix for almost any soil type or aspect, that has been extensively trialled and tested in government-funded research. Perhaps the most well known is the Silbersommer (Silver Summer) mix developed in 1990, which is a matrix of 20 fairly drought-tolerant, light-demanding and low-growing plants such as Salvia, Achillea, Phlomis russeliana, grasses and Geranium. You simply order the amount of plants you need and roll out the carpet. I have seen it in full flower at Weinheim and it is impressively natural-seeming, even if the concept is a little frightening Oudolf's early work at Pensthrope, in Norfolk, was very influential on British designers Dan Pearson (whose show at the Garden Museum opens on May 23), is one of the foremost British planting designers and perhaps the closest in style to Oudolf in the UK, has also recently been experimenting with matrix planting in a large Japanese project. But perhaps the extreme practitioner of the planting matrix approach is James Hitchmough at Sheffield University, who uses complex seed mixes rather than plants to create astonishing exotic meadows. While these are mesmerising on the big scale, and in the high season (from May to October) they don't have the appeal of an Oudolf planting in winter and don't work so well on a more intimate scale. For Oudolf, planting has always been about creating moods and eliciting emotions. But the recent, more ecologically informed work, gains an extra weight by connecting us to how plants grow in the wild. The design becomes much more about creating a plant community rather than a collection of individuals. To take one section of planting on the High Line, the plan shows a loose matrix of grass species planted throughout; in this case a mix of Panicum virgatum 'Heiliger Hain" and Calamagrostis brachytricha spaced about 1-1.5m apart with about 20 other varieties of perennial flower spread through in different-sized groups, from one plant used just singly to another planted in generous groups. The flowers therefore are always seen within a matrix of grasses, just as they might be in nature. These more recent plans, identifying the position of each and every plant, are of fabulous complexity. Oudolf told me recently how he works for months on these over the winter, in almost solitary confinement, and I am struck by the parallel between these drawings and the musical scores of some great orchestral colourist such as Debussy, where the complexity of the music can barely be contained on the page. The composer knows exactly the impact on the orchestral texture, for example, of introducing a few notes on the bassoon here, just as Oudolf knows the effect of adding another plant. The difference being that a composer can to some extent try out ideas on the piano, whereas the plantsman has only his memory and his sense of composition. It is hard to think of another creative arena where so much knowledge and understanding is abstracted and codified to such an extent; in the case of a planting plan, to be translated as a seemingly effortless expression of natural beauty in four dimensions. I walked the High Line this January on an icy grey morning. Everything was shades of brown, but there was a delicacy of line and a legibility to all the dead plants, which made it beautiful, even at that bleak time of the year. One can easily imagine the planting here translating to the most domestic and private of gardens. A repeat matrix is all very well for a big open space, but for finely nuanced spaces you need a master of detail. In Oudolf you have someone who thinks by the centimetre at the same time as by the hectare. Planting: A New Perspective" by Piet Oudolf and Noel Kingsbury (Timber Press, RRP £30) is available from Telegraph Books at £26 + £1.35p&p.