The Kalmia angustifolia is a small evergreen shrub native to North America.
Kalmia has quite slow growth, and with age it tends to form dense bushes with wide and branched foliage. The trunk has dark brown bark, sometimes tending to red; the branches are dark green, they turn brown with age. It has simple, alternate, elongated oval leaves, dark green on the upper side, light-greyish green on the lower side; in spring and summer it produces numerous flat, roundish flowers, with five slightly pronounced lobes, of pink or white color, gathered in dense clusters. In late summer the flowers are succeeded by fruits, small roundish semi-woody capsules, which break when ripe to release the seeds.
There kalmia prefers semi-shaded positions, which take the sun in the late afternoon, to prevent the leaves and flowers from burning; in colder climate areas they can also be placed in full sun. It does not fear the winter cold, it is more probable that the plant suffers for the sultry heat of the summer months. It can be cultivated with good results in different climates due to the rusticity of the plant but it is advisable to pay more attention to young plants that turn out to be more delicate.
The Kalmia angustifolia needs abundant amounts of water, especially in spring and in the months of flowering, it should be watered regularly, not letting the soil dry too much between one watering and another. In autumn and winter it should be watered with smaller quantities of water, without forgetting that the evergreen plants do not have a real rest period, and therefore require treatment throughout the year. In spring bury a mature organic fertilizer at the foot of the plant; during spring and summer, provide the plant every 20-30 days with fertilizer for flowering plants and occasionally fertilizer for acidophilic plants.
The plants of this species prefer loose, well-drained soils, possibly with an acid Ph; however, these shrubs are very rustic and grow even in poor and stagnant soils.
Thanks to its resistance this plant can adapt successfully to different situations and is cultivable even where conditions are not ideal, thanks to the ease of adaptation.
The multiplication of Kalmia angustifolia occurs by seed and is practiced in spring with the seeds collected the previous year; if desired in late spring you can also practice semi-woody cuttings, to be rooted in a container filled with a mixture of sand and peat in equal parts, which must be kept in a cool and damp place until the rooting of the cuttings is complete. The new plants and rooted cuttings must be grown for at least two years in a protected place before they can be planted.
Kalmia angustifolia: Pests and diseases
The kalmia plants are rather rustic and resistant but it is not infrequent that they are affected by white disease and root rot; sometimes they are attacked by aphids or mites that ruin the flowers and leaves.