Springtime is probably the most exciting season at the Royal Botanic Garden Edinburgh as its famous rhododendrons burst into colour. From shrublets to trees, they crop up throughout the Garden and real miniatures among rhododendrons can be found in the Rock Garden.
Worth seeking out is the snowdrop (Halesia carolina) tree from the US which has twigs hung with white bells resembling snowdrops. Aromatic new leaves from the balsam poplars add to the season by filling the air with a delightful scent.
In late spring, the Garden's lilacs put on a magnificent display and the star of the show is Syringa tomentella from western China. Its delicate, scented flowers are produced in great abundance and give a two-tone effect, their deep lilac paler on the inside and fading with age.
In spring the Alpine House must surely be one of the highlights of a visit to the Garden, with colours rivalling those of summer bedding but coming instead from some of the world's most delicate flowers.
Every plant here is a gem. Botanical treasures include plants of the primrose family and small deciduous orchids with large flowers in purple, pink or white.
The woodland areas are ideal habitats for primulas, which enjoy damp shady conditions, as well as the garden's Himalayan poppies (Meconopsis) that start to flower in late spring.
The Garden is renowned for its collection of Meconopsis with 18 species and several hybrids.
Late spring is also the time to admire the beauty of the peonies which flower in abundance. In the Glasshouses the jade vine should not be missed. For those wet spring days the Glasshouses also offer a profusion of orchids and flowering Vireya rhododendrons.
In summer, visitors flock to see the Herbaceous Border which provides colour throughout the season. With ample feeding and the protection of one of Britain's most splendid beech hedges, the perennials such as lupins, campanulas, delphiniums and phlox thrive.
Even the Arboretum, though arguably at its best in spring, also provides some summer colour with Philadelphus and late-flowering Magnolia. However, the most spectacular flowering tree must be the handkerchief tree (Davidia involucrata), so called because of its huge white bracts that flutter in the breeze.
Colour on the Rock Garden flows seamlessly from spring into summer, with sheets of pastel dwarf phloxes (Phlox douglasii) contrasting with mounds of yellow potentillas (Potentilla neumanniana) and the brilliant pinks of Morina longifolia.
The ponds in the Glasshouses are at their best in summer with exotic sacred lotus (Nelumbo nucifera), tropical water lilies flowers like Nymphaea 'Pamela' and particularly the giant Victoria water lilies (Victoria cruziana), whose leaves reach 1.5m to 2m in diameter.
As autumn arrives, plant growth starts to slow down and the change in foliage of most deciduous trees provides drama — falling leaves make way for a spectacular display of berries.
For some plants, autumn is not an end but a beginning. Many from regions with a hot, dry season take their vacation from active growth during summer and then burst into bloom with the onset of cooler, wetter weather. Colour in this "season of mists and mellow fruitfulness'' is provided by bulbous plants such as Nerine, Crinum, Amaryllis and Colchicum which have become so popular that their flamboyant pinks are now as much a part of autumn colour in gardens as golden leaves and red fruits.
A walk through the Arboretum is also a must as rowans and whitebeams combine brightly coloured fruits with attractive leaves that turn various shades of red, yellow and gold.
In the Glasshouses the theme continues with the abundant fruit of the chilli peppers.
Autumn is a surprisingly colourful time of the year in the Peat and Rock Gardens as well as the Alpine House. The highlights of the season in all these areas are undoubtedly the gentians and colchicums. Close by, the Scottish Heath Garden also provides interest as summer-flowering heathers hang on into autumn.
In winter, the Garden takes on a new and different character as views open beyond the leafless trees. The dormant season's delights — such as interesting bark, late berries, frail winter blossom or the new shoots of bulbs — may be few and far between but are nonetheless rewarding. Even in harsh weather, when the most stoical give up on the great outdoors, there are always the Glasshouses, where our love of colour and warmth can be indulged.
Winter-flowering trees and shrubs such as Mahonia and the evergreen Christmas box are a joy to behold. Near to the Alpine House is a bank of winter-flowering viburnums and a lawn surrounded by witch hazels. The Chinese and Japanese witch hazels flower from about December to March.
Yews and conifers play a dominant role in the landscape of the Garden at this time of the year. As well as providing a focal point, they also give shelter to plants including other conifers.
The Alpine House and Rock Garden still provide some real gems at this time of year. Depending on the weather the Algerian iris makes a show on the Rock Garden and the first signs of life arrive in the Alpine House in January with early birds such as a rare Turkish crocus and an orchid from Nepal. Earliest of the hoop-petticoat daffodils is a Narcissus from the Atlas Mountains in Morocco.
Cyclamen of one kind or another also flower during the winter months. Bulbous irises make a valuable contribution to the Alpine House display at this time of year.
No matter how hard the winter, Edinburgh's Vireya rhododendrons bloom as if it were spring. Vireyas are an eye-opener which most visitors acknowledge as a highlight, not just in winter, but throughout the year.
The Glasshouses are a must for visitors during winter. Tropical orchids provide a constant succession of flowers and in the Tropical Palm House plants such as the Asian rattan and wine palm have to be seen.