Silphium perfoliatum with tiger swallowtail butterfly
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Gardening is underpinned by plant finding, the essential impetus to a new design or a new arrangement of colour. When the basic bible, The Plant Finder, was first in preparation, I remember making fun of the idea. Why ever would we need an oppressive dictionary in small print listing every plant available in Britain? Surely we had enough of a struggle to cope with what we knew and grew already.

Maybe we are often scathing, with minimal acquaintance, about what we then go on to love. The Plant Finder volume is now in its 28th year. It is nowadays the RHS Plant Finder and it is everything that I once said it could never be. It has taken me to new nurseries, to new varieties of long-known plants, often much better than the old friends, and to new families of which I knew nothing. If you see a keen young gardener who has not yet consulted it, give her a copy and transform her horizons.

I am spending this August in England, poised for plant finding in new havens. It has to be better than sweating in sun cream. I am also looking out on the results of my random plant finding in recent years. It has brought me some August winners and transformed the range of particular families which I grew before the guide appeared.

Without the Finder, would I ever have come across Silphium perfoliatum, now listed with 14 suppliers, but in 1999, only deserving a single line in the book? It was 6ft high when I first saw it in a Gloucestershire nursery, covered in rounded single yellow flowers, and exactly the height which I need in later summer. I had no idea at that time that Silphiums are almost weeds in the US. There is nothing weedy about this excellent tall plant which needs no staking and looks elegant even when its fresh green seed heads survive the last of the flowers for the rest of this month. It is so easy to split up and usually drops a seedling or two nearby which can be transplanted elsewhere. One plant was enough of a buy. Once found, it suggested a transformation of a big border which needed backbone and more height at the centre from which either side could slope down. Silphiums are much tidier and longer-lasting than rusty hollyhocks, tied on their big canes. I had found a keynote and round it, an entire composition has developed.

Members of Plant Finder families multiply as editions of the book go forward. My candidates as the fastest-growers are the Crocosmias, still known to some of you as montbretias but far more rewarding than the basic old montbretia with its rushy green leaves and a few small orange-red flowers. I remember the excitement of a fiery scarlet Crocosmia, Crocosmia Lucifer, and its arching stems of flowers when they first appeared on general sale in the early 1960s. They will probably die in the frost, we all thought, but they did nothing of the sort. Lucifer is still a winner, a mainstay for a summer border, so far from dying it has been joined by dozens more. Some are new hybrids and selections. Others have simply come out of hiding, due to Plant Finder listings. The book drops on old varieties lurking in a modest nursery and brings them to our notice. If they are excellent, they then spread to other sources.

Crocosmia Emberglow

My pleasures at the moment are a dark red Crocosmia called Emberglow, a free-flowering red Fire King and two varieties named after the great Irish garden Rowallane, Rowallane Orange and Rowallane Yellow. I think of Ireland as the last home of forgotten crocosmias, lingering on in the good soil and damp climate since the days of prewar country house planting. What about Rowallane Apricot, listed as available from IBlr, which turns out to be Gary Dunlop at Ballyrogan Nurseries in County Down ( Without a Finder I would never know it exists.

Crocosmias are having a great year. The winter was wet, not cold and their corms have had a summer of intermittent sunshine, never so prolonged that they scorch. The Plant Finder now lists more than 200 varieties, an incredible profusion. Maybe you know the dark smouldering Emberglow, but what about Sir Mathew Wilson, Mephistopheles or even Tangerine Dream, named long before the rival tabloids gave the name to editor Rebekah Brooks? Crocosmias are members of the botanical iris family and grow from a cluster of small corms, best bought when growing in pots. They like to be in well drained soil but to have plenty of water passing through. My Emberglows glow best in a bed which is made more of fine grit than of soil. Few of the 200-plus from the Plant Finder have yet made it into expatriate Mediterranean gardens, but in a bit of shade, within reach of the irrigation system, I think they ought to be fine.

Crocosmia masoniorum ‘Rowallane Yellow’

In a week it will be time for my plant-found sort of hollyhock, one with leaves which reminded its first namer of the cannabis plant. The only addictive aspect of Althea cannabina is its cloud of pink flowers, held on slender stems to a height of 6ft. As t he stems are so graceful, you can see through and round the plant, allowing it to be used for sudden height and contrast in plantings whose centre of gravity lies at a lower level. It never blocks out the view or looks a leafy mess. It almost never needs staking and it always strikes a new note in dusty August. As its roots are long taproots, it ought to be in its element in hotter gardens abroad, but it seldom appears there, perhaps because local planters do not read our Plant Finder so closely.

This month I am on the trail of Campanula Lynchmere which I killed three years ago by a misplaced attempt to divide it. I want to refind a pink called Jane Austen now that I have the beds of gritty soil which dianthuses like her enjoy. I am sure I will hit on utterly unknown plants during the hunt, the silphiums of my future. There is so much out there, so excitingly.

Here is the crux. If you love the Plant Finder as I do, are you “just” a plantsman but never a “designer”? Garden designers are the people who like to say so, in self-defence, and I believe so firmly they are wrong. Careful plant finding does not have to end up as spotty collecting. A new plant, an extra-tall inula or a clear-coloured monarda, is like a new building block or paint tube in an artist’s care. It can suggest entirely new compositions or “designs”. Professional garden-designers are naturally wary about risking plant-found experiments which may well fail. However, good experiments then suggest others. A garden is not a paper drawing. It grows up over the years in dialogue with itself. One idea leads to another, but it is a difficult route for a “designer” to take as clients tend not to keep asking designers back every month. Meanwhile the designing career is one of new “projects”, not gardens as they evolve.

People like to ask what is “new” about gardens or “modern”. They hope to be told about brutally-brushed concrete or ornamental grass. I passionately believe that we are gardening at a great time of innovation, but the innovations are coming to us at the level of our paint tubes and components, the plants themselves. I will be following their impact in particular gardens during August, hoping to inspire you to Plant Finder on your return, to think, watch and innovate. You are the other partner in the well-planted garden’s duet.

Photographs: Tom Uhlman/Alamy; RM Floral/Alamy; GAP

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