Oleander

Oleander is one of the most popular container plants. This is how you properly plant and care for the Mediterranean flowering shrub.

Origin

The oleander (Nerium oleander), also called rose laurel, is the only species of its genus and belongs to the dog-poison family (Apocynaceae). The flowering shrub is one of the oldest and, because of its abundance of flowers, also one of the most popular Mediterranean container plants. It originally comes from Morocco and southern Spain and is now widespread across the entire Mediterranean region, India and China. The evergreen shrub was already valued in ancient times, as evidenced by Cretan wall paintings from the 14th century BC. The oleander spread around the world around 500 years ago. At that time it was reserved for the aristocracy and rich citizens, who adorned their orangeries with southern beauty.

Growth

The evergreen shrub can grow to a height of two to four meters and a width of up to three meters.

Leaves

The fleshy-leathery, lanceolate leaves are up to 20 centimeters long and three to four centimeters wide. There are three leaves on each shoot node – botanists speak of a whorled leaf position here.

Blossoms

At the branched shoot tips, umbels form several flowers. The wild forms each have five petals and bloom pink or white. Due to a variety of breeding, oleanders are now available in over 400 varieties and many colors: light and dark pink, salmon, light yellow, white and red. In some varieties, the flowers appearing from June to September are double or have a delicate scent. Caution: The shrub belongs to the Apocynaceae family – oleander is highly poisonous.

Location

For a rich bloom, the Mediterranean stars need a sunny, sheltered place. The more sun the oleander gets, the more flowers it sets. Oleanders therefore bloom significantly less in cool, rainy summers. Filled varieties should be set up protected from rain, since the full flowers can soak up the water, stick together and rot.

Substrate

Classic potting soil with peat content is not suitable for the oleander. The plant grows best in a predominantly mineral, calcareous substrate with a high proportion of clay or loam.

To water

Oleander is very thirsty, so you should water the container plant abundantly in summer. On very hot days, large oleanders should even be watered up to three times a day. It is best to place the pot on a saucer with a high rim that catches the excess water. The oleander can absorb this throughout the day and then often only needs water once a day. Since the oleander grows naturally in floodplains, it doesn’t mind wet feet – the pot can be up to a third in the water.

Oleander does not tolerate rainwater in the long term – this makes the soil in the bucket too acidic. The plant loves calcareous soil and therefore also calcareous tap water. Tempered irrigation water also promotes flower formation. Tip: Do not shower your plant over, but always water the oleander close to the ground, as moisture from above can damage the flowers and encourage the development of oleander cancer.

Fertilize

In order for it to bloom profusely, you need to fertilize your oleander regularly. So treat your plants to high-quality liquid potted plant fertilizer once or twice a week from March to September, which you add directly to the irrigation water. This ensures beautiful green leaves, dense foliage and vigorous new flower formation.

Repot

Since oleander is very vigorous, a young plant must be put in a new pot every year. The optimal pot for the shallow-rooted oleander is wide rather than high. Choose a planter that is about five centimeters larger and put in potted plant soil with a portion of clay granules and a little lime. Tip: If you want to repot large oleanders, you should tie the crowns together beforehand and water the root ball well – this will make the plants easier to handle and easier to remove from the planter.

Use

Oleander has a high ornamental value due to its long flowering time and its evergreen foliage and is often placed in bright corners and niches. Since the plant is very vigorous, enough space should be available. Alternatively, oleander can be grown as a standard stem. In a correspondingly large bucket, oleander is equally suitable for the sunny balcony, terrace and cold winter garden. It can be combined as a container plant with bay leaves, olives, bougainvilleas and numerous other Mediterranean container plants.

To cut

There are different reasons for pruning oleander and different ways of pruning. The container plant is fast-growing and easily tolerates pruning. Oleander can be pruned at any time of the year. So you can largely determine when the right time is. If the plant is obviously producing fewer flowers and new shoots are growing straight across the inside of the crown instead of outwards, you should definitely use scissors to tackle your plant.

Still, pruning should only be done when necessary for abundant flowering. The older branches tend to bare from below and often only have leaves at the branch ends. The joy of blooming also diminishes over the years. A makeover takes place in spring. To do this, cut back about a third of the oldest shoots to about 20 centimeters in length. Individual annoying, drooping or bare branches can be removed at any time throughout the year.

A pruning should only be made before putting it in the winter quarters if the plant has either been attacked by scale insects or has become much too big. Of course, you can also remove sick shoots. You should be careful with this pruning, as the plant has already created the buds for the next year.

If necessary, an oleander can also be “put on the stick”, that is, it is cut down radically. This may be necessary, for example, because of a strong pest infestation or because the oleander is balding from below. Late winter is the best time for such a radical pruning. The plant will regenerate quickly and grow nice and bushy. In this case, however, a new flower cannot be expected until the following year, since all the flower buds that have already been created are removed when cutting. After a strong pruning into the old wood, the oleander always only forms vegetative, flowerless shoots in the first year. A slight pruning of a maximum of a third of the length of the shoot leads to the formation of shorter new branches that open their flowers from around the end of July. Important: Wear gloves for all cutting measures, as the toxic milky sap that escapes irritates the skin.

Wintering

Since oleander is only frost-hardy to around -5 degrees Celsius, the plant must be protected from excessive frost in winter. The ideal wintering quarters is a cold winter garden or unheated greenhouse, a so-called cold house. Alternatively, the oleander can also be overwintered in the dark in the cellar or garage, but the temperatures should then not exceed five to ten degrees Celsius. Rule of thumb: the darker the room, the lower the temperature should be when the oleander is overwintered. In order to prevent an infestation with scale insects, a low room temperature is recommended even with good light. A temperature between two and ten degrees Celsius is ideal. In closed rooms you should ventilate once a week.

First the plant is cleaned: remove colored leaves, withered flowers and damaged or diseased branches. You should then check the oleander for pests. If the plant is infected, take countermeasures such as pruning or treating it with pesticides. If it is too big for winter quarters, you should also cut it back. However, we recommend – if possible – to wait until spring before pruning, otherwise the oleander can sprout too early.

Check them regularly for scale insects in air-dry rooms. Water occasionally, because the root ball must not dry out completely in winter. It is normal for the oleander to lose a lot of leaves in the dark winter quarters – they drift back in spring.

If you live in a milder region, you can also overwinter the oleander outdoors by covering it with a fleece hood and placing it outside in a shady, sheltered place with a well-insulated pot. A location close to the house wall is ideal. In order to keep it warm enough, you should first take care of good floor insulation – for example with a styrofoam sheet under the planter. If you don’t have too much space, you can tie the branches of the oleander together with sisal cord. This is also very practical, because you can easily wrap your plant and pot with coconut mats or bubble wrap and protect them from frost. However, be sure to leave a spot for occasional watering.

Tip: Some nurseries offer a wintering service for container plants. So if your oleander has gotten a little too big, just ask the nursery you trust. The plants are also optimally cared for over the winter.

Sorts

Oleanders come in many colors with single or double flowers, sometimes even with variegated foliage (for example “Splendes Variegatum”). Those who want to avoid the classic pink tones can choose the white ‘Alba’ or the red ‘Little Red’. Double flowers represent ‘Madonna Grandiflora’ in white, ‘Luteum Plenum’ in light yellow and ‘Mrs. Roeding ’in salmon color on display. If you like it gaudy, the best thing to do is to choose the dark red variety ‘Algiers’. ‘Papa Gambetta’ is a compact, very easy-care variety with an orange-red flower color. ‘Roseum Plenum’ has particularly large flowers of around seven centimeters.

Multiplication

There are different methods of propagating an oleander: by cuttings, division, grafting and sowing. The easiest way to propagate oleander in spring is by cuttings from the head, which are produced when the plant is cut. Peel the twigs and place them in the water glass or root the cuttings in a pot with potting soil in a warm, bright place. When the first strong roots have formed, the cuttings can be transferred to a pot of potted plant soil. Older plants can also be propagated by dividing the root ball. Slightly cut back the newly created plants when potting; they will sprout again quite reliably. The other two methods are not recommended for the hobby garden and should be left to the specialist.

Diseases and pests

Yellow leaves on the oleander indicate care errors or a wrong location. However, various diseases and pests can also make life difficult for the oleander. The first aphid infestation threatens at the beginning of May – the oleander aphid is easy to recognize by its honey-yellow color. As a result, dark sooty fungi often appear. Silvery speckled leaves indicate spider mites. Woolly webs in the leaf axils and on the underside of the leaf indicate mealybugs and mealybugs. Oleander cancer, which is caused by bacteria and is contagious, can be recognized by small black spots surrounded by a light border, which later bulge and break up, as well as black twigs and crumbling thickenings on the flower branches. If your oleander is already infected, you should remove all infected leaves early on and cut the damaged shoots back into the healthy wood.

Tip: After cutting out the infected shoots, disinfect the scissors with 70 percent alcohol from the pharmacy to prevent other plants from being infected.

Which soil is suitable for the oleander?
The oleander prefers a predominantly mineral, calcareous substrate with a high proportion of loam and clay.

Which fertilizer is suitable for an oleander?
The oleander is fertilized either with a slow release fertilizer or with a high-quality liquid fertilizer that is added to the irrigation water.

How much water does the oleander need?
In contrast to many other Mediterranean plants, the oleander needs a lot of water and is sensitive to drought. Therefore you should water the oleander regularly: from spring to autumn at least once a day – on hot summer days even twice. In winter it is enough to water the shrub twice a week.

When do you have to repot an oleander?
Since the oleander is very vigorous, young plants in particular should be repotted once a year. The new plant pot should be about two inches larger than the old one.

When can you cut oleander?
Oleanders are cut back before they are put into their winter quarters. But theoretically you can cut it all year round. A pruning is especially advisable if the shrub has fewer flowers.

How much frost can the oleander tolerate?
As a Mediterranean plant, the oleander is only frost-hardy to -5 degrees Celsius. Oleanders are best overwintered in frost-free winter quarters, or the shrub is provided with winter protection in mild regions.

Why does the oleander get yellow leaves?
Yellow leaves can have various causes: incorrect care, a wrong location or plant diseases. Make sure that the pot is big enough, that the root ball has not dried out, that the location is not too dark and that the fertilizer dosage is appropriate. Also, check the leaves for pests such as lice. Oleander cancer can be recognized by small black spots that are surrounded by a light border. The twigs turn black and thickenings appear on the flower twigs.