Rhododendrons are one of the most impressive flowering shrubs in the garden at this time of the year.
This year rhododendrons are flowering better than ever due to the high rainfall we had last summer. Rhododendrons are shrubs that can reach tree-like proportions. They form great profusion of colour as branches become obscure by the beautiful flowers. They are found growing all over the world. The different species range from enormous trees that reach up to 100 feet tall through to alpine shrubs a few inches high. Rhododendrons are now available in a range of flower colours that cover the whole spectrum of visible colours, some of them are strongly scented.
Rhododendrons need an acid soil with a pH of 5 or less. If the soil pH is higher, around pH6, it is possible to grow rhododendrons in the open ground, provided they are treated with an appropriate acidifier to help prevent the leaves turning yellow and sick looking. In limy soils it is best to grow rhododendrons in raised beds or containers. Plastic sheeting should be placed under the raised bed to prevent seepage of limy ground water into the bed. Fill the bed with a lime free compost enriched with well rotted compost and some conifer pine needles. Rhododendrons are shallow rooted, so it is important to plant them at the depth as they were growing in the pot. Do not hoe or dig around the plant to avoid disturbing the roots. Once planted, rhododendrons need very little attention and if grown under ideal conditions will not require feeding or pruning. To control weeds and to keep the roots cool and moist apply a layer of wood bark around the plants. Do not fertilise because it will stimulate fast growth that produces long weak stems and few flowers. Deadheading after flowering will improve growth and direct all the plant’s energy into the formation of new flower buds. Keep rhododendrons well watered, especially during the summer when the following year’s flower buds are forming. It is best to use rainwater, as tap water can have a high pH level. Rhododendrons will grow in dapple shade with some protection from cold winds.
Rhododendrons are easy to transplant due to their compact fibrous root-ball. They can be transplanted any time but autumn is the best. Rhododendrons are difficult to propagate and it takes time to produce a good size plant so they are expensive plants to buy. If you have limy soil in your garden you can still grow these beautiful plants in a raised bed or containers.
Rhododendron ‘Blue Tit’ is a compact dwarf shrub that grows 3 feet tall and produces blue flowers. Rhododendron ‘Fragrantissimum’ grows 6 feet tall, producing white flowers with a strong scent. Rhododendron ‘St Breward’ grows 3 feet tall with red flowers. Rhododendron ‘Goldkrone’ grows 5 feet tall and produces golden yellow flowers.
At present the uncontrolled spread of Rhododendrons has led to it being considered an invasive pest which can have a very negative impact on woodlands and rivers. If kept under control within a small garden it can add colour but beware that unchecked it can become quite large.
Azaleas are closely related to rhododendrons. Azaleas are grouped under the general title of rhododendron, but most gardeners look on them as a separate plant. Japanese azaleas are small evergreen and free-flowering. They will grow to about 3 feet tall and like a sunny position. Deciduous azaleas are larger shrubs that produce a profusion of funnel shaped flowers in a range of colours, some of the flowers are scented. Azaleas require the same growing conditions as rhododendrons. Rhododendron mollis is a deciduous azalea that produces orange-red flowers.
Jobs for the week
If you haven’t already now is a good time to tidy up the spring flower dead heads such as daffodils that might have been providing nice colour back in April but are now looking unsightly. Ideally if the green leaves are still healthy leave them for another few weeks to soak up energy for next years growth, it is still too early to divide and replant but with flower heads removed and spot of high potash fertiliser the bulbs will continue to absorb nutrients during the coming months improving chances of more flowers next Spring.
Boyce’s Garden at Mountrenchard, Foynes is open daily to the public.