Soul and spirit of every garden; They bring colour, character and charm, so sniff out some of these perfect herbaceous perennials and wait for their moment to shine in your plot.
PEOPLE are always asking what my favourite plant is. I find it impossible to answer. Quite apart from the fact you'd be offending all the others if you chose just one, different plants steal the limelight at different times.
Herbaceous perennials are the basis of our garden. Yes, shrubs and trees provide structure throughout, but the real soul and spirit, its essence, emanates from these wondrous perennials.
With rich crimson pin cushions all summer long, Knautia macedonica is indispensable. It is just one of the perennials I couldn't be without.
Pollinating insects gorge on it and its seedheads are useful for birds.
We never deadhead it, both for the birds' sake and because they are so pretty. It makes a shrubby plant about 2ft both ways.
My mum gave us a white phlox that we've increased year on year.
It hasn't got a name apart from Jeannie's phlox.
There are countless varieties of Phlox paniculata, varying in colour from almost red, such as "Prince of Orange", to the mysteriously lilac "Eventide".
|Sometimes phlox develop mildew but forms of Phlox maculata seem impervious to it.
They have a more graceful form, with flowers loosely arranged around the top half of the stems.
And they are not at all fussy about soil as long as they are well fed.
Eryngium The daisy family is the most populous flowering family in the world. Daisies of all kinds make gardeners smile.
There are at least a dozen suitable for every place, though the majority prefer sun.
One of the best - and a plant I make no apologies for using over and over again - is Aster "Little Carlow", with clouds of blue flowers on strong stems. It seldom needs staking.
I have a soft spot for umbels of every kind - plants from the family apiaceae.
Most have white flowers in the manner of cow parsley, in others such as fennel they're yellow.
Unexpectedly, astrantias and eryngiums belong to the same clan.
If I had to choose only one it would be Selinum wallichianum.
Each flower head becomes a plateau composed of tens of smaller florets, which in turn are made up of myriad tiny flowers.
The flower heads are impeccably fashioned, their plates perfect circles composed of smaller circles.
How could I leave out sea hollies? Eryngiums are in vogue - but were they ever out of it? Their spiky flower heads fit into any naturalistic planting and, as long as they have reasonable drainage and a sunny position, they will live for many years.
| Knautia macedonica, above and Aster 'Little Carlow' All the species can be grown from seed and this year we're trying Eryngium alpinum "Blue Star".
It looks as prickly as can be but in fact feels soft.
Heleniums are stalwarts of the herbaceous border - an American family that crossed the Atlantic almost three centuries ago and have dwelt in our gardens ever since.
During the past few decades, several plant breeders, especially in Germany and Holland, have produced remarkable new hybrids.
Though I've always liked them, it wasn't until I saw "El Dorado" the year before last that I really sat up and took notice.
It is like pure sunshine - large, bold flowers of pure yellow and a pleasant deportment make it an exceptionally good plant.
Most of the plants chosen so far are great mixers and give a good account of themselves for months.
Peonies, too, have lots to offer, with pretty, often pink, foliage in the spring and glossy foliage that can turn crimson in the autumn.
Their flowers, though, are short-lived, lasting only a week or so.
But while they are at their peak, there is nothing more voluptuous in the plant world.
I could go on - we've hardly scratched the surface and shade-lovers haven't had a mention.
The choice is yours, of course, and there are endless possibilities.
As long as we choose straightforward plants that nonetheless offer us beauty, longevity and character, our gardens will be happy places.
| Selinum wallichianum | Peony
"There are countless varieties, varying from almost red to mysteriously lilac" - Carol Klein
| Super fan.... Carol admiring the phlox at Glebe Cottage PICTURES: Jonathan Buckley/Getty