10 herbaceous plants Carol Klein says to grow in your garden now — including beautiful asters

"This is just fabulous for the summer," delights Carol, smiling from ear to ear about this plant, which has the most beautiful lacy umbels.

"It's from the family Apiaceae – which used to be called Umbelliferae – and is a true perennial umbel because lots of them are short-lived annuals or biennials. It will go on, year after year."

Commonly known as Wallich Milk Parsley, it originates from the Himalayas and first emerges from the ground in the shape of a large doily.

"Come early summer, it throws up these huge stems, at least a metre tall, with lovely flat heads of tiny star-shaped white flowers," says Carol, "which the insects love."

If you have a soft spot for those white fluffy clouds of cow parsley growing along country roads in early summer, then you will be smitten by this.

"To see this plant from a distance," muses Carol, "you would think a mass of small butterflies had just landed on it. It has these elegant, long stems which produce small, white, delicate flowers that look like they are fluttering in the breeze."

It is also known as Bowman's Root and originates from the US, where it grows on the edge of woodland. So, while it does like the sun, it also doesn’t mind a bit of shade and is quite a tolerant perennial.

"It will flower for at least a month, if not six weeks," says Carol, "But come autumn, there is even more to see when its dainty green leaves turn the most gorgeous shades of russet, burnt orange and crimson."

No wonder it has the RHS’s Award of Garden Merit. A flower with wings to steal your heart.

"I think these plants are fabulous anywhere," declares Carol, "with their gorgeous, glowing, bright, yellow petals and what I like to call large dark brown ‘doorknobs’ at the centre. The Helenium is a member of the daisy family, which is the biggest flowering plant family in the world, and comes in every shade from buttery yellow, orange and crimson to reddish-brown and bronze."

It needs sun but is also frost-hardy and will bloom from July until late October.

"In the spring, it's also a great one to propagate," says Carol. "The plant comes in clumps, and, in March, you can dig one up and divide it into several pieces and just plant them individually."

The bumble bees will also love you when they see this one – and we do like to keep our bumble bees happy!

Commonly known as the Large Bellflower, who can resist the pretty purple bells of this native harebell that has been a favourite of British gardeners for years? Carol finds them irresistible.

"This is a smashing plant which grows about a metre tall," she says. "The bells are tubular-shaped, a couple of inches long and appear right the way up the stem. They can be white, as well as blue, but down here in Devon, where I live, we have an abundance of beautiful pale mauve ones, which have dark purple centres."

They self-seed and come in tubular, bell-shaped, and star-shaped varieties, too. "Just in case you're looking for another one to join it, I also love ‘lactiflora’, which has milky bell-shaped flowers and is much taller."

Why have one when you can have two of these pretty darlings?

Next on Carol's list is an award-winning member of the aster family, which is now called a Symphyotrichum.

Its common name is Michaelmas daisy because it starts to flower in late summer and continues to do so right through September and into October – the Feast of St Michael, otherwise known as Michaelmas, falls on September 29.

"The stems grow up to 3ft and from each one comes masses of vivid violet blue daisies with golden gem centres and toothed dark green leaves," explains Carol. "And, luckily, they don't need any support. In the autumn," she adds, "butterflies, such as the Brimstone, have a second hatch, so this beauty is an absolute treat for them, as well as us."

Whether you lean towards the English cottage-style garden or the wilder prairie planting trend, this violet treasure will come up trumps.

"This is one of my absolute go-to herbaceous plants," raves Carol, who has them all over her blue and yellow garden.

"It has oceans of sunshine yellow daisies with striking black centres. Not only do they catch your eye, but they are so easy-going to look after – the only exception being they don’t like the soil to be too dry."

Most of these late asters originated in the prairies and will spread out of their own, but as Carol hastens to add, "They are not invasive but equally are great to dig up and divide in the spring if you want to add them to another part of the garden. The other plus is that the seed heads are gorgeous, so birds and bees will love them."

Finally, they also make a great cut flower. A great way to bring colour to the darkest room in the house!

There's nothing like a tall ornamental grass to add height and texture to a garden and this one sits at the top of Carol's grass list. “This is my absolute favourite," she declares.

"It’s a bright green Japanese grass and although you can get a variegated version, I love this plain one because it just looks so elegant, in other words, what I would describe as having a beautiful deportment."

When you can look at a plant all year round, it’s got to be special. "I’ve only just cut them back," explains Carol, "because even in the winter, the leaves add so much interest to the garden, and by early spring, new shoots are coming up."

You don’t need to grow it in the ground. With a bit of sun, it will look just as wonderful in a pot, blowing in the wind on your balcony.

"Everyone knows them and everyone can grow them," says Carol, of the flower that comes in every shade you can think of, from ivory white, peach and coral to rose pink, blood red, lilac and mauve.

"No one can mistake their fancy feather-shaped stems, which can reach up to 85cm and are made up of hundreds of tiny flowers that, together with their fern-like foliage, love to sway in the wind, explains Carol. "They will happily fill your garden with colour from mid-June to late August when their jazzy colours will begin to mellow and turn into earthier tones to complement the rustic autumnal shades of its foliage."

It originates from China and Japan, but one of its more common names here is the rather unflattering False Goat's Beard. But like so many flowers, it has come to symbolise a virtue, and for Astilbe it is patience.

And of all the virtues a gardener might need, patience is definitely one of them.

Greatest Gardens with Diarmuid Gavin and Carol Klein is a new six-part gardening series on the hunt for the best garden in Northern Ireland.

The first five episodes are available to watch on BBC iPlayer after episode one airs on BBC One Northern Ireland on Monday 23 March. The grand finale will be broadcast on BBC One Northern Ireland and BBC iPlayer on Monday 27 April.