Rhododendrons belong to the Ericaceae family. Subfamily Ericoideae, genus Rhododendron is represented by 850 species, the majority of which can be found in China and in the Himalayas.
Customarily, a Rhododendron with evergreen leaves is considered a rhododendron, while those representatives of the Rhododendron genus which shed their leaves for the winter are known as azaleas. The majority of rhododendrons have considerable requirements in terms of habitat which make it impossible or largely difficult to grow these plants in our climate. The primary condition for successful cultivation is acidic soil (pH = 4-5). The ground must be permeable, moderately humid. Heavy, compact and overly wet soil is unsuitable. The site ought to be shaded or semi-shaded, shielded from the wind. The place for a rhododendron must properly prepared. To this end, dig out a hole 80-100 cm in diameter, and approx. 30-50 cm deep. Depending on the ph of the original ground, add 50 to 80% of acidic peat, and mix it with this ground, or with sand or sandy soil. If the site is too humid, drain it before planting rhododendrons. Due to the shallow root system, it is advisable – once you have finished planting – to cover the soil with a thick, 3-5 cm, layer of bark. While choosing a specific variety, make sure to check its resistance to frost. Some varieties have a tolerance up to minus 30 degrees, while others, especially those imported from western Europe, may only resist frost of up to minus 18. Rhododendrons must be covered for the winter. Snow is the best cover but if there is no snow, tie a string around the plant to reduce its volume and wrap it with non-woven crop cover or double-folded shading net. We usually perform these activities in mid November, and we uncover the plant in mid March.
Characteristic pitting on leaves may be a sign of the presence of snails or even worse – of black vine weevil. Larvae of that beetle can gnaw on the root collar, causing the death of the plant. In such a case, water the plant with a systemic agent e.g. against potato beetles.
You may successfully fight fungal diseases, which may occur especially if humidity is too high, by watering your rhododendron with a wide range of effects, such as e.g. Mildex at a concentration 0.2%.
Healthy growth and blossoming is usually worth the trouble, as it gives a rare spectacle lasting 3-4 weeks, usually in mid May. If you plant rhododendrons in large groups, the effect is even more sensational. The plants in question like the company of other Ericaceae, Leucothoe, Pieris plants, Japanese azaleas but also birches, and columnar and creeping junipers.
Family matters. Family of... Ericaceae.