All gardens have their own shape or form which can be enhanced by beautiful shrubs. These can give an extra dimension of height, and if evergreen can add interest in the winter time.
Rhododendrons are of great value in laying out the skeleton of a garden, coming in so many sizes and foliage types, and all flowering profusely in spring.
There are four basic sizes of rhododendron, large, medium (yakushimanum hybrids), low-growing and alpine.
The large hybrids are familiar to most people and reach about 2 metres after 12 years. They shouldn’t be confused with the common rhododendron ponticum which is a weed. There are many flower colours ranging from white, to pink, red, yellow and orange, and look wonderful when planted around the edges of medium to large gardens.
Yakushimanum hybrids grow to medium size, around one metre after twelve years. They arose following the discovery of an exciting new species of rhododendron in 1934 on the remote Japanese island of Yakushima. The plants were found growing on the rain-drenched and wind-swept slopes of the island’s mountain peaks. This new species was hybridised with many of our large-growing rhododendrons to produce the extensive range of compact plants that we have available.
In the 1950s and 1960s breeding programs were carried out by Percy Wiseman and Gerald Pinkney at Waterer's Nurseries to produce many good plants including my favourite Rhododendron Percy Wiseman. At Hydon Nurseries A George produced the seven dwarfs series, many of which we list today. Hachmann in Germany has produced some stunning varieties such as Rhododendron Fantastica.
As well as lovely flowers in many different colours, the foliage provides interest as some varieties and especially the species has leaves coated underneath with a luxurious furry indumentum. The species also has this present on the top of the leaves, like the bloom on a freshly picked plum.
The yakushimanums provide the opportunity to have fabulous rhododendron flowers in today’s smaller gardens. Pleas follow this link for details of the RHS trial on these shrubs: www.rhs.org.uk/Plants/RHS-Publications/Plant-bulletins/Rhododendron-yakushimanum-Bulletin
Low-growing rhododendrons are smaller, growing to about 60 cms and are useful near the front of the shrub border.
The alpine varieties generally grow to no more than 30 cms and can be used in places such as the front of the border or on the rock garden. They‘re covered with a mass of flowers in early spring, starting in April, before the main rhododendrons.
All rhododendrons need an acid soil. If you are in any doubt about your soil, check your neighbour’s gardens to see if they can grow rhododendrons, azaleas or pieris. Alternatively a simple pH testing kit can be bought from a garden centre. If your soil is alkaline you can still grow rhododendrons in containers around the patio. Be sure to use an ericaceous compost. The yakushimanum hybrids as well as the low-growing and alpines will all do well in planters. For neutral soils it is beneficial to feed the plants twice yearly with sequestered iron, available form you local garden centre.
Rhododendrons can be planted at any time of year, though if in spring or summer they will need watering during dry spells until the roots are fully established in the ground. They benefit from the addition of bark or peat in the planting hole, and a little bone-meal helps. Do not use fresh farmyard manure as it can burn the roots. If there is any yellowing of the leaves then a fertiliser rich in iron can be used (eg ‘Sequestrene’ or seaweed fertiliser with added iron for ericaceous plants).
All our rhododendron are very hardy and this winter have sailed through temperatures of minus sixteen with no damage, smiling at us through the snow.
Azaleas like similar growing conditions to rhododendrons. if planting in containers then the evergreen azaleas are particularly suitable, growing only to about 60 cms in height. They look stunning in the garden when planted in a drift, to give a bed of vibrant colour in spring.
The azaleas are divided into two types ; evergreen or Japanese and deciduous. The evergreen azaleas grow to about 2 - 3 feet, and some are very low growing e.g. Azalea Mount Seven Stars which can be grown as an alpine. The North Tisbury Hybrids are a special group bred by Polly Hill at Martha's Vineyard, Massachusetts in the 1960s. These flowers a month later than the mainstream, starting in June, and thus they prolong the season. They are also mostly very low growing, e.g. azalea Pink Pancake which reaches only 10".
Deciduous azaleas often have rich autumn leaf colours giving an extra season of interest. Some varieties are scented, notably the delicious azalea luteum with yellow flowers. These plants grow to about 1.8 metres after 12 years so are suitable for planting towards the back of the shrub border. They have a beautiful soft appearance and give two seasons of interest so are invaluable in the garden.
Herbaceous Perennials These form the beautiful tapestry of the garden flowing between shrub plantings, or forming beds of mixed or themed colours (for example a blue and yellow garden at Clare College, Cambridge). There is nothing quite so spectacular as herbaceous borders in late spring, summer and early autumn. There is a huge range of colours, textures, heights to choose from and these plants can be used like paints on an artist’s palette to truly create an original garden. On a more modest scale individual plants can be used to brighten up corners or patio planters when the form and colour of the flowers can be enjoyed close-up.
Tall plants like delphiniums, lobelias and digitalis can be used at the back of a planting, whilst low-growing plants such as erodiums, phlox subulata, anacyclis, small geraniums etc can go at the front and phlox paniculata, anthemis, echinaceas etc in-between. Some taller varieties may need staking with twiggy supports pushed into the soil early in the season, but we try to grow varieties that are strong enough to stand up on their own.
Many early flowering varieties will give a second flush of flowers if cut back just after flowering in June or early July.
Plants can be made to bush out and give more flowers if cut back to about 20 cms in spring, though the same effect can often be obtained by lightly trimming the tops of the shoots.
After plants have been growing for a few years they can be lifted and divided to provide new plants to give to your friends or plant in other places. If some well-rotted manure is dug in before replanting this will invigorate the plants.
We are raising some lovely varieties, carefully selected to perform well and be resistant to disease. We also have many exciting plants in the pipeline which will be ready for sale in the next year or two.
Finally, perennials always look better planted in groups, at least three of each. This can be done when lifting and dividing to provide drifts of each variety.
Hydrangeas are a puzzle when it comes to pruning as many people find that the following year there are no flowers. The rule is that for paniculata types pruning can be hard in late winter and they will still flower the same year. This group includes Hydrangea Unique, Kyushu, and Pink Diamond. Hydrangea Annabelle can be treated the same way although it is an arborescens variety.
Mophead and Lacecap varieties usually skip the next year’s flowering if pruned after July. Note that rmoving dead flower-heads is OK and not the same thing as hard pruning.
There is a wonderful report by the RHS on the wonderful paniculata hydrangeas: www.rhs.org.uk/Plants/RHS-Publications/Plant-bulletins/Hydrangea-paniculata
Magnolias These lovely shrubs grow in neutral or acid soil. Some of them will flower a a very young age, especially the stellata types. The white flowered varieties look stunning when planted against a dark background such as a yew hedge of dark fence or wall.
The soulangeana varieties also flower young and have tulip-shaped blooms.
Alpines These plants normally grow in rocky well drained places and this gives a clue as to how to grow them. Incorporate plenty of drainage material such as gravel or grit in the compost. Some plants with rosette formation in the leaves, such as lewisia, grow best on their side in a wall.
Rhodohypoxis do well in a raised bed or sink garden where the soil is relatively dry. Both these varieties are borderline hardy. However they have both survived -16 degrees this winter in an unheated polytunnel, proving that being over-wet is more dangerous for them than being too cold.