Iwan helps Natalie and Richard to add flowers that suit the period and character of their house in Rhiwbeina.

Delphiniums are one of the classic flowers of the traditional summer garden.

Their tall upright spikes laden with intensely-coloured flowers are a feature of herbaceous borders, where they are best grown near the back to add height and drama.

The plants look best grown in a group with several other varieties in shades of blue and cream.

Rosemary is a bushy shrub with a dense, leafy habit, to 2m x 2m but variable in size.

Linear dark green leaves and its flowers are usually a pale violet-blue and white.

Flowering starts in spring but is often repeated at differing times of year.

This is a version of the popular lavender named after Laurence Johnston's Arts and Crafts garden.

It produces highly fragrant violet flowers during the summer. It's possible that this is the best lavender for pathway edges and borders since the fragrance lifts as you walk past.

It's a favourite for bees and other nectar lovers!

Cut the stems back after the flowers have faded.

Cut back carefully in April making sure you don't cut into the old wood.

S. byzantina is a carpeting, evergreen perennial, with thick, soft, oblong-elliptic leaves and stems densely white-woolly.

Basal leaves are to 10cm long, in rosettes, flowering stems erect to 50cm in height.

Flowers are purplish or pink, sometimes appearing striped, arranged in many-flowered whorls in an interrupted spike in summer.

Several selections with varying leaf and flower colour are available. A valuable foliage plant

Herbaceous peonies differ from woody-stemmed tree peonies in that they die back to ground level every winter.

Unjustly, peonies are often considered difficult to grow, but with some basic care they can provide colour and enjoyment for many years.

• Ideally plant in full sun, though a few will tolerate light shade
• Most prefer neutral to slightly alkaline soils; some such as P. anomala are best planted in slightly acid soil
• Good drainage is essential
• Feed with a balanced general, fertiliser such as Growmore in the spring.
• The flower stems may not be strong enough to keep the often heavy flamboyant flowers upright and staking is often required
• It is generally best to cut the foliage to ground level as it dies back in the autumn to reduce risk of peony wilt

No garden should be without this beautiful and useful perennial. It has scalloped, bright green leaves which catch droplets of water that look like quicksilver and from June to September, it produces a frothy haze of tiny, chartreuse yellow flowers. It's ideal planted en-masse for groundcover or edging paths. Alchemilla mollis takes its name from the Arabic, meaning little magical one, as in the middle ages the water collected from its leaves after a morning dew was said to have healing properties.

Cut back the faded flower heads and foliage in August and the plant will often produce a second flush of flowers. Alchemilla has a tendency to self-seedfreely, so to minimise the spread of the plant remove the seedheads carefully after flowering.

Related to catnip, but much showier, catmints (Nepeta) are easy to grow perennials that not only have flowers in shades of purple-blue, pink and white, but gray-green foliage that remains attractive throughout the growing season as well.

Bergenias are indeed one of the season's most valuable plants.

Most bergenias are evergreen perennials with leathery rounded leaves up to 30cm (12in) across that rise from a stout, iris-like rootstock. Some make tight clumps while others develop a more open habit.

Bergenias are undemanding, growing happily in shade or sun as long as the soil is not too dry. Colour is often better in less fertile soil while spring foliage and flower is more impressive in richer conditions.

The Foxglove (Digitalis purpurea) is a biennial or short-lived perennial, freely self-sowing, with a rosette of softly hairy, oval leaves and tall, one-sided spires of pendant, tubular, bright rosy-purple flowers 6cm long.

Growing nicotiana in the ornamental flower bed adds a variety of color and form. Excellent as a bedding plant, smaller cultivars of the nicotiana plant reach only a few inches, while others may grow as tall as 5 feet. Various sizes of the nicotiana flower can be used at the front or back of a border and provide a sweetly fragrant experience on calm days and especially in the evening. Flowers of nicotiana, flowering tobacco (Nicotiana alata), are tubular shaped and grow moderately to quickly. Too much fertilization when growing nicotiana can lead to excessive growth of the petite plants causing them to get leggy and cease flowering or flop.

Origanum vulgare is a bushy, woody-based perennial with small, aromatic, ovate leaves and panicle-like clusters of small pink flowers in summer and early autumn

Cosmos atrosanguineus is a spreading tuberous perennial, with pinnately divided leaves and bowl-shaped, chocolate-scented, maroon-crimson flower-heads in late summer.

The Clematis montana species of clematis are very vigorous growers, and are great for growing up through trees, along hedges, over garages, up houses (anywhere that they have room to grow freely) they flower in abundance in May and June, available in pinks and whites and doubles and singles.

This fantastic plant flowers for about nine months of the year and gently Self-sows into all the nooks and crannies. A brilliant value plant which no garden should be without.

Will self-seed and spread with it's roots making it perfect for walls and paths. Deadhead to encourage flowering.