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Azalea - Growing Guide
GROWING DECIDUOUS AZALEAS
While evergreen azaleas prefer partial shade and damper soil conditions, deciduous azaleas are even tougher and, arguably, even easier to grow. They dislike shade, which inhibits their flowering potential, and grow best in full sun. They will readily tolerate hot, dry, stony locations and thrive even in arid sandy locations.
These are plants which develop into multi stemmed shrubs growing (after quite a few decades) in maturity to perhaps 8-10ft in height and, often, with a somewhat similar spread. As with evergreen azaleas the best effect comes from growing them in bold banks of one particular colour rather than mixing different coloured flowering varieties which may not all grow at the same speed.
Like evergreen azaleas, but probably even more so, they have no worries about being cut down hard to 2-3ft from the ground to rejuvenate elderly specimens which are not flowering as well as they should. This also allows you to get rid of the ivy which often hides within mature clumps.
At Caerhays and Burncoose there are a number of clumps of deciduous azaleas which are now 80 to 100 years old and still going strong even without the occasional pruning. There are a few varieties which we stock that are old Ghent, Knapp Hill or Exbury hybrids which have stood the test of time but many newer varieties of deciduous azaleas have appeared on our list in recent years which are from more recent hybridisation work.
A few deciduous azaleas have exquisite smell. Azalea pontica (or Rhododendron luteum as it properly is) remains perhaps the best but there are others.
You can see a selection of our deciduous azaleas in the photographs below this article where we have attempted to show how they actually grow in gardens.
Unlike evergreen azaleas, deciduous ones are extremely difficult to propagate from softwood cuttings in June or July. The success rates are often small and, even when rooted by the autumn, they still die off when dormant over the winter. Deciduous azaleas are therefore best grown from layers or from seed where you are certain that no bee or insect has cross pollenated the flower from another nearby plant. This means that you have to self-pollenate the flower and then cover it with a paper bag until the flower itself dies off.
Anyone who has a little room can grow and enjoy a deciduous azalea in any garden that has acidic or neutral (but not heavily alkaline) soil.
GROWING EVERGREEN AZALEAS
All evergreen azaleas are, in fact, properly classified as being part of the genus rhododendron. There are well over 600 different species of rhododendrons which can be grown outside in our UK climate and far more if one includes tropical species. From these have come many tens of thousands of hybrid rhododendrons. It is a vast genus and it has therefore suited gardeners to make life a little easier by commonly referring to them as ‘azaleas’.
Evergreen azaleas are grown in most woodland gardens and in many town and country gardens for their extraordinary floriferousness which occurs mainly in April. Some varieties are so covered in flowers that, for a time, one can hardly see any of the leaves. The plants themselves mature at a height of 6, 8 or 10ft after many decades and are long lived plants. They are often grown in large groups for maximum impact as at the Punch Bowl evergreen azalea planting in the Valley Gardens a Windsor. At Burncoose and Caerhays there are many large established banks and clumps of evergreen azaleas many of which were collected from Mount Kurume on a Japanese island by Ernest Wilson, one of the great plant hunters. In the early part of the last century Wilson gathered together what is still known as the ‘Wilson 50’ of Kurume azaleas. Several of these original varieties still thrive in our gardens and a few of the best of them are still offered on our website. They have very unpronounceable Japanese names and, in more recent times, breeders have introduced new hybrids with even larger flowers and less awkward names. You can see photographs of all the varieties which we stock below this article mainly in garden settings. Sadly none of them are scented in flower.
Evergreen azaleas are perfectly hardy and easy to grow. They do best in moist soil conditions in locations where they get at least some dappled shade for part of the day from nearby tall trees. Full shade is not a good idea. Evergreen azaleas do need wind protection from cold east winds which can defoliate them a little and sometimes scorch and kill them as small plants. They may need watering in dry periods for the first year or two.
Mature plants of most varieties can be rejuvenated by cutting them back to 2-3ft from the ground to allow them to reshoot and probably, given time, produce more, larger flowers.
Evergreen azaleas are easy to root as softwood new growth cuttings in June when the new growth has not hardened off and is still soft and bendy. These should be rooted with bottom heat and potted on the following spring. Evergreen azaleas seldom set much, if any, seed.
In gardening terms these are solid reliable mound forming shrubs of great merit which are easy to grow. They will only grow in gardens with alkaline soil where beds can be created with more acidic soil or the addition of peat to change the pH of the soil conditions.
3 featured azaleas - Video Tip
1. Az. ‘Caerhays Lavender’ (evergreen) 2. Az. ‘Black Hawk’ (evergreen) 3. Az. ‘Melford Lemon’ (deciduous)
Ernest Wilson's 50 Karume Azaleas from China - PDF & Gallery