Beautiful but Poisonous Oleander

In short: Oleander (Nerium oleander) is an evergreen shrub growing up to 4 metres tall, and every part of it is poisonous – the leaves, stems and flowers contain glycosides such as oleandrin. Grow it in a bright spot with rich soil, water and feed it generously, and overwinter it at 2 to 12 °C.

Oleander (lat. Nerium oleander) is an ornamental shrub belonging to the dogbane family (lat. Apocynaceae). Oleander is also known as rose bay. The original homeland of oleander is the area stretching from the Mediterranean through northern India, Burma to China. Within such a wide distribution range, considerable variability has been observed, which is why 6-8 species of oleander were distinguished in the past.

Today, botanists agree that the distinctive characteristics are not strong enough to recognize separate species, so they have returned to the original view that there is only one single representative of the oleander genus, namely Nerium oleander. Only the former species Nerium indicum, which has angular branches, has more distinctly different characteristics. However, breeding has produced many cultivars flowering in various colors - from white, through yellow to dark pink. Crossbreeding has also achieved double flowers and fragrance in some cultivars. The yellow-flowering, double-flowered and fragrant variety is named Nerium oleander "Luteum Plenum". The Latin name "Nerium" has a Greek basis in the word "neros" meaning wetland. The name suggests where the plants originally grew. Wild oleanders grew by rivers and in their flood areas. Therefore, when growing oleanders, don't skimp on water and provide them with enough nutrients to mimic their natural habitat.

History of oleander

Oleanders were cultivated as ornamental plants as early as the beginning of our era. They are even considered to be the first plants to be grown in pots for ornamental purposes. The original flower color of oleanders is pink. In the 16th century, a white-flowered cultivar was developed in Crete. Fragrant varieties were bred in the late 17th century. The cultivation of a yellow-flowered variety at the beginning of the 19th century was considered the peak of breeding achievement. To this day, yellow-flowering oleanders are rather rare.

Description of oleander

Oleander is an evergreen shrub that can grow up to 4 meters tall under ideal conditions. Oleander leaves are smooth, leathery, narrow in shape, approximately 10-15 cm long and about 3 cm wide. The leaves are dark green with lighter veining. The petioles are short. Raceme inflorescences form at the end of one-year-old shoots. Flowers come in various colors and can be single or double depending on the cultivar.

All parts of the oleander including the flowers are poisonous!!! Therefore, be careful to keep small children away from it.

Poisons Contained in Oleander

The leaves, stems and flowers of oleander contain glycosides (e.g. oleandrin, neriine and neriantin), which make it highly poisonous. Glycosides tone the cardiac muscle and have a strong diuretic effect. Symptoms of poisoning include vomiting, dizziness, arrhythmia, convulsions and fever. Severe poisoning can, in the worst case, even result in death. If poisoning is suspected, do not induce vomiting and immediately call the emergency services or your local poison control centre. Any gastric lavage and administration of other detoxification agents will then be carried out by medical staff. The sap contained in oleander can cause skin inflammation. In sensitive individuals, the scent of oleander flowers may cause headaches and dizziness.

Growing Oleander

Oleander thrives best in a bright location, in very nutritious soil. Suitable soil can be composed, for example, of 4 parts turf, 2 parts leaf mould, 2 parts rotted manure or hotbed soil and one part sand. In its homeland, oleanders grew in nutrient-rich river deposits, so it is advisable to water and fertilise them sufficiently during the season. Fertilisation is recommended every two weeks with a special combined fertiliser for indoor plants. Use settled, soft water for watering, as oleander is quite sensitive to water hardness. To achieve flowering, you must summer the plant. Move it to an outdoor sunny location when there is no longer any risk of frost. In warmer weather, water the oleander daily. It is advisable to place the plants in a covered spot, as their flowers are susceptible to moisture and during prolonged rains they turn brown, become mouldy and fall off.

Move the plant to its winter location at the end of September (depending on the current weather). Oleander can tolerate frost down to approximately -10 °C for short periods. Although frost will damage young shoots, the plant can reliably sprout from older wood or produce new shoots from the roots. However, oleander would not survive prolonged frost. If possible, overwinter oleanders in a cooler environment with temperatures ranging from 2 - 12 °C. More sensitive cultivars should be overwintered at temperatures of 8 - 12 °C. At temperatures above 12 °C, the plants awaken to growth. Warmer overwintering may also cause weaker flowering in the following season. Another factor affecting flowering is the extent of leaf loss during the winter period. The more leaves fall off, the less the plant is likely to flower.

To prevent leaves from falling off, they need plenty of light even in winter. Conversely, plants overwintered in cold conditions need a minimum of water - only enough to prevent the roots from drying out completely. Despite all care, some leaf drop may occur during winter, which is completely natural in our climatic conditions. However, leaves will not regrow in their original place, so bare twigs should be cut back in spring.

Oleanders grow back very well, but keep in mind that newly grown shoots will only flower in the following season. If you don't have the opportunity to provide oleanders with overwintering in a cool location or in a winter garden, don't despair - the plants will survive warmer overwintering as well. However, they require sufficient light and watering like other houseplants. If you're growing oleander near central heating, give it regular misting, especially during winter. Repot oleanders in spring, older specimens only need repotting every 2-3 years. You can partially shorten the roots. When repotting, don't forget adequate drainage in the container. Oleanders are not prone to diseases or pest infestations. Young plants can be grown from seeds. The most suitable time for sowing seeds is spring and summer, when the climatic and light conditions are best. Sow seeds in humus-rich soil. Keep the soil constantly moist. For sowing, you can use a mini greenhouse or mini propagator, which will help maintain sufficient moisture and correct temperature. Transplant grown plants into a suitable container.

Interesting fact in conclusion

Despite the entire oleander plant being poisonous, the leaves collected during flowering are used for medicinal purposes. The drug obtained from them can regulate cardiac activity and treat skin rashes. However, its use in folk medicine is not recommended as it is very risky!!! The poison in oleander leaves was used in the past to exterminate rats and mice.