10 hardy annuals to plant in April for months of colour, including striking snapdragons

'With their carnival shades of orange, red, and yellow, these cheerful annuals will flower and flower and flower, keeping you company well into late autumn,' says Rosy. 'Again, there are so many varieties to choose from, but I've gone for a slightly more unusual one called ‘Jewel Cherry Rosy' which has this delicious crimson-pink colouring that looks so pretty crawling along a border or tumbling over the side of a large pot.'

They are more than happy in poor soil; in fact, the flowers prefer it, and every part of the plant is edible, from the seeds (otherwise known as capers and often added to salads) to the petals, which will steal the show on a summer sponge or lemon meringue.

'It always brings back memories of my childhood,' says Rosy. 'In the summer, I'd go round the garden biting off the long spurs in the middle of the flowers which contain the nectar – it was like drinking honey.

'This is one of my absolute favourites,' says Rosy of this enchanting pale blue flower with its tiny feathery green foliage. 'I always have it running through my gravel garden so that come the middle of the summer, it starts to look like a sea of blue. They come in various pastel shades, including a cream pink, and all of them have these distinctive long stamens in the middle.

'One that I find particularly exceptional,' continues Rosy, 'is Albion Black Pod, which has creamy white layered petals and dark green stamens. This is so named because when the flowers fade, its dramatic, burgundy-coloured seed pods really stand out.'

It may be small, but its exquisite architectural shapes are monumental.

'It's the foliage as much as the flower that wins this more unusual annual a place on my list. Gardeners are simply drawn to the gorgeous milky tones of its blue-grey leaves, which are often covered in silver speckles. From these, emerge arching purple bell-shaped flowers which are surrounded by dark purple bracts.'

It originates from the Mediterranean – you can still see it growing wild in Greece. The name Cerinthe comes from the Greek word keros, meaning ‘wax’ and Anthos, meaning ‘flower’, as it was thought that bees got the wax for their hives from this flower. They are indeed nectar-rich, so bees love these flowers to get their fill of nectar.

Before sowing the seeds, soak them overnight in warm water to soften their hard coats and help them germinate, then sow in a sunny sheltered spot – a stony area would be ideal. They will shine and shimmer for you.

'The summer wouldn't be the same without a few umbels – the wonderful group of annuals that always bring an ethereal touch to any garden,' says Rosy.

'And I just love this one because, as well as its delightful green feathery foliage, its large umbel flower heads turn from vivid lime green to refreshing apple white.'

The word umbel comes from the Latin word ‘umbella’, meaning ‘parasol, sunshade’, and, like many of them, this could look like a dainty parasol. Plant seeds now and they will reach a metre in height and flower from June until September.

'They are joyous, they lift your spirits,' says Rosy. 'And like many of the flowers on my list, they are a great cutting flower, whether it be for a summery display in the living room or an elegant outdoor wedding tablescape.'

So much splendour from one little seed.

'From crimson and lipstick pink to velvety purple and marshmallow white, this summer favourite has such a range of jazzy colours that it's hard to pick out a single one,' says Rosy. 'But if I'm pushed, I'd say it's hard to beat the mesmerising contrast of two shades – the peachy-apricots and the rich, dark burgundies.

'They also vary in height, and my preference is for the taller ones for that mid splash of colour in the borders, or on their own in a pot.' This is often referred to as a half-hardy annual, so many gardeners start them off in trays inside.

'The main thing is ensuring the frost has gone to give them their best chance, and to do several sowings,' says Rosy. The Romans loved them; the Victorians loved them. With their Bridgerton summer-ball charms, we do too.

'Every summer, this flower brings me so much joy,' says Rosy, clearly besotted by this wonderful white umbel, which loves to shimmer in the sun and sway in the breeze.

In recent years, many gardeners have embraced a more informal style to their summer planting; some have even opted to turn their entire garden over to long ornamental grasses and wildflowers. And the umbellifer family of flowers epitomises this style with glorious height and movement.

The question is: which of them is the prettiest of all? For Rosy, it has to be White Lace Flower (Orlaya grandiflora). Or is it Queen Anne’s Lace (Daucus carota)? It’s so hard to choose! In fact, the names alone make you want to grow them and see for yourself their gentle magnificence.

'This annual is commonly known as mountain spinach, or red orach,' says Rosy. 'It is still grown as a spinach-type vegetable, but such is the beauty of its deep purple foliage, that it has become a favourite ornamental in many gardens,' she adds. 'And of course, it also looks striking in a summer leaf salad.'

It prefers full sun, and when left to grow to its full size, which can reach 4-5ft, spikes of tiny magenta pink flowers emerge from tall slender red stalks.

'I've been growing this for years and would often include them in my Chelsea Flower Show displays where they would always get a huge amount of interest from visitors,' adds Rosy.

Not only that, but the flowers are followed by wonderful seed heads, which just prolong their presence well into the autumn. Spinach has never been so attractive!

'There is something rather magical about this sweet ornamental grass that I find so attractive,' says Rosy. With a bit of imagination, this grass does indeed look like a magic wand, even a sprinkler on Firework night.

'It has bright green broad leaves which often have a purple tint to them, and from its centre emerges these soft feathery flowerheads which look like mini silvery firework explosions. And although they always bring a gorgeous hazy feel to a garden border, I actually grow them in containers because I love the way it arches over the sides, showing off their elegance even more.'

If you are still dipping your toe into the world of ornamental grasses, this silver wand will enchant you all summer long.

You can watch Rosy Hardy's tutorials on her YouTube channel Rosy Hardy Gardening.