Roddy Milne, our Head Gardener , loves to share his passion for plants. Each week throughout the month we will add one of his favourites….

Impatiens tinctoria

Impatiens tinctoria

I find that there are certain plants which are worth growing – not because they are particularly beautiful, but because they have a specific asset, an alternative social use or perhaps only because they come from somewhere unusual. Impatiens tinctoria is one such plant.

Impatiens tinctoria is the largest growing Busy Lizzy you will ever encounter. The usual types you see, often in hanging baskets, only grow about 40cm tall, whereas this sort will, when happy, reach over 2 metres. The tall, leafy stems develop each year from a Dahlia-like tuber and from August onwards produce butterfly shaped, slightly orchid-like flowers near the top of the stem. They are night scented, being pollinated by moths, and have a heady tropical scent (if such a thing exists).

Impatiens tinctoria comes from central Africa – from the cool, higher elevations in Ethiopia and south to Tanzania. Here, a red dye is obtained from ground-up tubers and this is used as a beauty treatment, being applied to the palms of the hands and feet. It also controls fungal infections and toughens the skin.

Despite coming from central Africa it is relatively hardy in British gardens especially in the milder parts such as Pembrokeshire. It is worthwhile leaving the old frosted stems on the plant through the winter as this will protect the massive underground tuber from the worst of the cold. It will grow in full sun and enjoys plenty of moisture.

Impatiens tinctoria is a relative of the pernicious weed Himalayan Balsam and has the same type of highly entertaining exploding seed pods but will not spread endlessly like its counterpart. For me, despite its wonderful scented flowers. it is worth growing for the fun to be had in exploding the pods.

Hydrangea paniculata

Hydrangea paniculata

I think this year in particular, various colours of Hydrangea are putting on a fantastic floral display in virtually every garden throughout the County. They have a great density of flowers in every shade of pink and blue – the exact colour of which is dependent on the type of soil they are growing in.

There is one type of Hydrangea that is a little bit different from the types normally seen, even though it is widely available from garden centres and nurseries. It is Hydrangea paniculata and it has big ‘panicles’, up to a foot long, of white or creamy-white flowers. This loose, more open, flower structure is a welcome change from the rather solid looking form of the normal type of Hydrangea.

If left unpruned Hydrangea paniculata will grow to become a large shrub up to eight feet tall, but with an annual pruning the size can be maintained to the height suited to the location. It differs from other Hydrangeas (which, incidentally, will not flower if the height is reduced annually) in that pruning encourages the production of extra large flowers. What we do here at Picton is let them grow freely for a number of years until a suitable size is reached then each winter after that the annual growth is cut back, leaving just a couple of inches of the previous seasons growth. From this stub of wood will sprout new shoots that will bear a large flower at this time of year. This task of pruning is a very pleasurable gardening job.

Hydrangea paniculata is an easy plant to grow and will thrive in any garden position that is not too extreme. It will also flourish in shade where other Hydrangeas will not flower and in this location the wonderful white flowers look especially fresh and bright.

The Narrow Leaved Lacebark

Hoheria augustifolia

There are a large number of garden plants that originate from New Zealand. Some like the New Zealand Holly (Olearia macrodonta) are well known to gardeners, especially those next to the sea where its tolerance of salt spray make it very useful.

There are however some treasures of immense beauty that are rarely seen in British gardens. One such race is the New Zealand Lacebarks (Hoheria) which I think are among the most beautiful of all flowering shrubs. I called them shrubs, however all types of Hoheria have the capacity to grow to become smallish trees up to eight metres tall. They are especially valuable because the delicate, airy, white flowers of Hoheria are a welcome change from the rather dense and repetitive displays of Hydrangeas that are the trademark of this time of year.

If you have the room all Hoherias are worth growing, however, my favourite is Hoheria angustifolia, the Narrow Leaved Lacebark. It is the type that seems to grow best here in Pembrokeshire although I plan to continue experimenting with others. When young, The Narrow Leaved Lacebark grows quickly and with a vertical habit. Then, as it matures, it becomes more pendulous and displays masses of little white flowers right along its weeping branches. It has small pale-green, evergreen leaves.

To grow well, all Hoheria should be planted in a sheltered location in soil that does not dry out severely. They are worth planting somewhere where the intricacy of their five petaled flowers and their delicate scent can be easily appreciated.

Three Jolly Bishops

Dahlia Bishop of Llandaff

Dahlia Bishop of Llandaff

Dahlias are not for everybody. They have a reputation for producing massive, oversized, multi-coloured flowers of an infinitely complex form. Many types are big, almost coarse, leafy green plants that are hard to mix subtly with other garden plants. They are also best lifted from your garden each year, stored and replanted in spring in order to avoid the cold winter months. Slugs also love them, so it is little wonder most gardeners avoid them.

There are however three lovely varieties that can be hard to resist. I call them the Bishops. All three are moderately sized plants with dark-purple leaves; each variety is a slightly different shade from the other. They have single flowers about four inches across, each a dramatically different colour from the other varieties.

Dahlia Bishop of York

Dahlia Bishop of York

The variety ‘Bishop of Llandaff’ with vivid scarlet flowers is by far the most popular and widely grown. The ‘Bishop of Canterbury’ has a bright purple flower that unfortunately bleach a bit in the sunshine and I find its rather artificial colouring hard to place sympathetically in the garden. My favourite is the ‘Bishop of York’ with its simple yellow flowers which look lovely against the dark purple, slightly matt, foliage. Its cheerful flowers mix easily with other orange, pink or blue flowers. All these varieties start flowering in June and will continue until the first frosts of winter. After this it is wise to dig up the tubers, cut of the tops of the plant that has grown that year and store the tubers in a dry, frost free place. In the spring the tubers can be potted up and watered. Soon growing tips will appear and then once the frosts have finished the potted plant can be planted in your garden where it will grow rapidly and soon start flowering. Slugs usually have to be controlled and it is also worth removing spent flowers to encourage the production of new ones.

Beautiful Bergamot

Monard Squaw_Beautiful Bergamot

Monarda didyma, better known as beebalm or bergamot, is a very attractive garden plant with aromatic leaves which have an odour similar to that used to flavour Earl Grey tea. I was delighted to find out last week that the British National Collection of Monarda is located at Glyn Bach Garden, right here in Pembrokeshire, and that the Garden was open under the National Garden Scheme that weekend. A visit to this inspiring and beautiful garden renewed my fascination for these wonderful plants.

One plant that was particularly thriving was the red flowered Monarda Squaw, which also grows well with us here at Picton Castle. It is a tall, strong growing variety with intricate tubular flowers arranged in a terminal whorl, typical of Monarda. Monarda are herbaceous perennials, so the flowering stems grow and then die back to the roots annually. They come from eastern North America where they grow in woodlands or woodland fringes. As garden plants they require moist soil throughout the summer months and do not enjoy hot dry conditions.

There are many different varieties of Monarda and in a good range of colours including vibrant red, pink and purple. It is worth choosing varieties that are less affected by mildew fungus which can disfigure the leaves and cause them to drop off, leaving a rather naked looking plant – a problem that is much alleviated by growing them in moist soils. There is more information about Monarda and some nice pictures too, on the Glyn Bach Garden website.

Belladonna Lily

Belladonna Lily

Many of you will be familiar with the large bulbs of ‘amaryllis’ that are often given as Christmas presents and which, when potted and watered, produce a massive lily-like flower. These plants are in fact Hipperestrums which originally come from South-America. Closely related is Amaryllis belladonna from Cape Province in South Africa which can be grown outdoors in our gardens. This plant is commonly known as ‘Belladonna Lily’ which is perhaps a reference to the poisonous qualities of all its parts – the name being borrowed from the Latin name for ‘deadly nightshade’. It is also known as ‘naked-ladies’ which comes from the plant’s habit of flowering before any foliage appears.

The green leaves are produced early in the spring and have completely died away by August when a flower stem emerges from the ground. This grows to around eighty centimetres tall and then large pink flowers emerge on the end. The absence of leaves makes this quite a curious sight. Each individual bulb can keep flowering for at least fifty years. ‘Belladonna Lilies’ like growing in hot sunny places and the ideal place is right at the base of a south facing wall where they will be quite dry and baked during the summer months. Once they are established they are best left undisturbed indefinitely. The clump we have at Picton growing right against the castle is at least fifty years old and produces about twenty-five flower stems each year.

Scottish Thistle

The Scottish Thistle or Cotton Thistle (Onopordum acanthium) is a thistle of giant proportions. It is a biennial plant, meaning it lives for just two years: the first being spent as an attractive leafy rosette of large silver leaves, and the second growing into a towering silvery flower stem that can reach up to three metres tall. On top of this are the fiercely armoured purple thistles that are much loved by a huge range of nectar loving insects including many species of bees, which love to loll around amongst the mass of filaments that make up the complex flower. After the flowering is complete the whole plant sets loads of seeds and then dies, emerging the following year as a mass of seedlings.

When in flower they are spectacular and dramatic and provide a strong seasonal structure to a border. Like most ornamental thistles they are very drought tolerant and actually relish growing in poorly fed soils. The Scottish Thistle is native to arid parts of Mediterranean Europe and has somehow managed to become the national emblem of Scotland since at least the 15th century.

Rice-paper Plant

I really like big, leafy plants. Perhaps this is because I work in a big, leafy garden where big leaves are easy to accommodate. ‘Rice-paper Plant’ or Tetrapanax papyrifer is definitely grown for its large, pale green, slightly felty leaves that can be up to sixty centimetres across. These are held in neat rotation around a stout stem which grows to about three metres tall, and in mild winter the plant remains evergreen. In cold winters the whole shrub can be killed back to ground level however it nearly always sprouts again from the base or from suckers produced from the roots. When happy and in a sheltered place, Tetrapanax will form a thicket of individual stems that are easily dug out should they stray too far from where intended.

Tetrapanax is endemic to Taiwan and is widely cultivated in Eastern Asia and other tropical areas. When rice-paper was first introduced to Europe around two hundred years ago it was assumed that it was derived from rice, and the name rice-paper came into use. Rice paper is in fact made from the pith from Tetrapanax stems which are cut and boiled, then have the bark removed after which the remaining pith is rolled out to form ivory-white paper. The plant is also used in Chinese medicine.

Growing a ‘Rice-paper Plant’ in your garden will certainly add a dramatic, almost tropical statement. Even a recently planted small plant will be of spectacular proportions by the end of its first summer.

Canna ‘Wyoming’


Canna Lilies have been used by gardeners for a great many years to add an exotic touch to planting schemes. They were used widely during Edwardian times in immaculately planted and maintained formal bedding borders and many town councils still use them as ‘dot’ plants to provide contrast and height within parks and, where money permits, on roundabout planting. Cannas also grow widely in the tropics and, being very rich in starch, are grown for human and livestock consumption. In Thailand they are the traditional Fathers Day gift.

Gardeners have bred a great many varieties with large bright flowers and handsome foliage. There are small varieties suitable for pots and monsters growing over three metres in one year. My favourite is one called ‘Wyoming’ that has dusky purple leaves and contrasting orange flowers. When happy it grows to about two metres tall and the purple leaves provide a lift to the abundant green summer foliage of other plants. All Cannas love sunshine, water and plenty of  food so they are currently having a good year!

In mild winters Cannas will survive fine outdoors, but watch out for slugs in early spring. If you suspect a cold winter it is wise to lift the rhizomes and store them in a dry, frost free place.

A Special Hydrangea


Everyone must be familiar with the great pink or blue ‘Mop-Head’ flowers of the Hydrangea, a fantastic summer flowering shrub. Much as love their flamboyance and the quite subtle changing of colour as the flowers age, there are many other less gregarious types to grow. Some varieties, such as Hydrangea involucrata, need to grow in sheltered woodland conditions whilst others such as Hydrangea paniculata, can grow to become a small, attractive tree.

Hydrangea serrata ‘Grayswood’ is an excellent and easily accommodated garden plant. It has smaller leaves than the ‘Mop-Head’ type and only grows to just over a metre in height, making it ideal for most gardens. During July it has delicate looking blue flowers,sometimes tinged red, and it will flower reliably every year. Very little maintenance is required except for possibly cutting out some of the oldest wood about once every three years. It will grow happily in full sun or part shade and, like all Hydrangeas, likes moist but not waterlogged soil.