Clethra is a medium-sized shrub with deciduous leaves, native to North America; the mature specimens can reach 150-200 cm in height, with an erect and roundish habit. They produce erect stems, well branched, covered by a dense, oval, pointed and dark green foliage; in autumn, before falling, the foliage becomes golden yellow. During the summer at the apex of the stems numerous small white flowers bloom, delicately scented, gathered in long cob lilies up to 20-30 cm. The flowers are produced on the branches of the year, so it is possible to prune the plant at the end of winter to maintain a compact shape and to favor the development of new branches and therefore of panicles of flowers. There are numerous cultivars with variegated or mottled foliage or with pink flowers.
Regarding the ideal exposure, the Clethra prefers sunny or semi-shady locations; cultivation in the shade causes a low production of flowers and often leaves of reduced dimensions. Does not like excessively dry or very hot places. It does not fear the cold and can withstand even very intense and prolonged frosts. It is therefore suitable for cultivation in the open ground, it does not present particular problems for the arrival of the winter season.
As for watering, from March to October water the Clethra plants regularly, especially during the hottest and driest times of the year. We try to keep the soil fairly wet; often these shrubs are planted near streams or small ponds, where they can enjoy a continuous supply of water; they are very suitable even in areas close to the sea.
To allow an adequate development, this variety of plants needs to be planted in acid, fresh and deep soil, very rich in organic matter; therefore, remember to avoid watering with excessively calcareous water, and to use a suitable substrate for acidophilic plants, enriched every year with mature manure; periodically we fertilize with special greening fertilizers for acidophilic plants. The ideal soil must maintain the right degree of humidity, as these plants love soils with water.
The Clethra plant produces small dark berries, which often remain on the branches for several months; collections can be used as seeds; in summer it is possible to practice semi-woody cuttings, taking small portions from the branches that have not produced inflorescences and burying them in a soil suitable for allowing the new plants to take root. Once they have acquired sufficient strength, it is possible to permanently place them.
Clethra: Pests and diseases
Specimens belonging to this variety fear the attack of mites, especially during the summer season; if grown in unsuitable soil they may suffer from ferric chlorosis. If signs of pests or diseases appear, it is advisable to intervene promptly in order to be able to effectively counter the problem; on the market there are special products available that will definitively solve the attack of pests or provide the necessary elements to counteract ferric chlorosis.