Flowering time (month)
October to December
Ornamental or utility value
The poinsettia is botanically named Euphorbia pulcherrima and is also known under the German names Adventsstern, Christstern or Poinsettie. It is a spurge species and belongs to the spurge family (Euphorbiaceae). The poinsettia is usually kept as an annual houseplant, although in its original form it is neither a pot plant nor an annual. The poinsettia is actually a persistent, evergreen shrub from South America. The star-shaped leaves of the plant already enchanted the botanist Carl Ludwig Willdenow, who gave it the botanical species name Euphorbia pulcherrima – “the most beautiful of the spurge plants”.
Only since the 1950s has the poinsettia been known in the United States as a houseplant. Since then its popularity has grown and despite its seasonality, the Christstern has become one of the best-selling indoor plants in the world. The garden centres offer a large selection of plants, especially during the Advent season. Attention: Poinsettias are poisonous! As with other spurge milk species, the latex of the poinsettia contains slightly skin-irritating components. After consumption, small pets such as cats, rabbits, birds or hamsters may show signs of poisoning. Consider this when purchasing and placing the plant in your home and wear gloves when repotting and cutting your poinsettia so that you do not come into unnecessary contact with the latex. In principle, skin contact is harmless, but the latex of the plants can cause allergic reactions in sensitive people.
If you encounter the poinsettia in its South and Central American homeland, you will be amazed: there you will stand opposite an expansive shrub up to six metres high. The compact growth of the unusual potted plants is artificially induced by chemical inhibitors and, of course, by the limited root space in the pot. The richly branched, bushy plants are usually only 50 to 60 centimetres high and 40 to 45 centimetres wide. The poinsettia is also available as a tall stem and in mini format.
The poinsettia forms large, pointed, egg-shaped or lanceolate leaves. At the tips of the shoots, rosette-shaped, colourful leaves appear, which lead to a widespread error: The coloured stars for which the plant is traded at Christmas time are not the flowers of the plant. These are so-called bracts. In the wild form of the poinsettia, the bracts are always red. However, there are also cultivars with creamy white, yellow, pink or variegated bracts. However, poinsettias with blue, silver or golden leaves are not of natural origin – they are produced by colour sprays.
The actual flowers of the poinsettia are the small yellow-green formations in the middle of the leaf star, which could be mistaken for pistils on a cursory glance. At the outer edge, lip-shaped nectar-glands sit, that are arranged individually or in pairs. With them, the poinsettia attracts various flying insects in its tropical homeland to pollinate the flowers. The potted plants flower from October to January. Tip: If you want to buy a long-lasting poinsettia, make sure that the small flowers in the centre of the bracts are still closed and have not been sprayed with paint.
The poinsettia wants to be bright, but not in the full sun. At 18 to 20 degrees Celsius, the flowers last much longer in winter than in very warm rooms. But the poinsettia is not only sensitive to high temperatures, but also to cold and draughts. Especially in supermarkets and DIY stores, which offer a large number of poinsettias from November, the temperature requirements are often hardly taken into account. It is best to make sure that your poinsettia has not been too cold right on the spot, transport it well packed and do not place it in a place that is too cold or draughty at home, so that you still have some of the red-green beauty for a long time to come. Advent stars are particularly sensitive to cold draughts – they then tend to discard their leaves.
Euphorbia pulcherrima can spend the summer outdoors in a bright location without direct sunlight, but should be brought back home as soon as autumn sets in and the thermometer reads below ten degrees Celsius. In autumn, the shorter days stimulate flowering again. Place the plant for about six weeks in a place that is not artificially lit in the evening, for example in the stairwell or in a cellar with a window, in order to further stimulate flowering. If this is not possible, cover your poinsettia in the early afternoon with a large cardboard box until the bracts have re-coloured themselves again.
The right substrate for the poinsettia
Since the soil of the pot ball in newly purchased poinsettias is often inferior and the water does not hold properly, repotting is recommended at the latest after flowering. Cactus earth has proved to be a good substrate, as it stores little moisture and the roots of the poinsettia, which are sensitive to waterlogging, tolerate watering too often better than when very humus-rich soil is used.
Water your poinsettia too little rather than too much, because Euphorbia pulcherrima does not tolerate waterlogging at all. It is best to immerse the houseplant in an immersion bath every seven to ten days, depending on pot size and humidity. The potting soil may dry out a little in between before you water the poinsettia again. If the leaves turn yellow and fall off, this indicates that the roots are too wet. If the poinsettia leaves its leaves hanging, which is particularly easy in direct sunlight, it is too dry. Always equip the pot with a saucer so that excess water can drain off.
In spring after the flowering period – around March – the poinsettia can be kept almost completely dry for a month. In the growing season from April to autumn it should be watered again with plenty of room warm water. The bale should always be moist and must never dry out, otherwise growth will stall. In the winter months you only have to water the poinsettia a little.
From spring to autumn you should supply the poinsettia with flower fertilizer on a weekly basis, in winter every two weeks.
You can repot the poinsettia annually in spring or summer. Use a new pot that is only slightly larger than the old one: In containers that are too large, the poinsettia would unfold splendidly and develop many leaves, but only a few flowers and bracts. If, on the other hand, it is kept like a bonsai in limited root space, it remains compact and – with proper care – very flowering.
After the coloured bracts have been thrown off, the perennial poinsettia can be summered over without any problems with a little care and will produce its coloured leaves again next year. To do this, cut your poinsettia back strongly after flowering and repot it into a fresh, permeable substrate.
Further care tips
After Christmas, when it loses its red bracts, the poinsettia is often simply discarded – wrongly, because if you follow a few care tips, you will get something from it for a long time. Just like the Christmas cactus (Schlumbergera), the poinsettia is a short day plant. It forms new bracts and flower buds only at less than twelve hours day length. In our latitudes this is the case from October. However, the brightness of artificial light in the living area usually lasts much longer than the poinsettia needs to produce flowers. If it is exposed to light for longer than twelve hours, it enters the flowering strike and forms only green leaves: the late riser just needs its beauty sleep.
In the United States, nurseries take advantage of the fact that the poinsettia’s flower formation is triggered by exposure for a maximum of twelve hours. From October onwards, they cover their greenhouses with black foil, so that the poinsettias are led to believe that a correspondingly short day will be a reality. And voilá – together with the blossom the red stars appear punctually to the Advent season. Tip: If you darken the short-day plant for 12 to 14 hours a day for about two months starting in September, for example by putting on a cardboard box, you can simulate the tropical light conditions and make your poinsettia bloom again in time for Christmas.
In addition to the classic red poinsettias, there are now numerous poinsettias in unusual colours on the market. Poinsettias from the Princettia series, for example, start flowering in September and offer a wide selection of colours, from rich pink to pink and orange to brilliant white.
The best way to propagate the poinsettia is to use cuttings. These occur continuously during pruning in spring and pruning in summer. Cut the cuttings to a length of seven to ten centimetres and dip the ends from which latex emerges briefly in water to stop the bleeding. The cuttings are then placed in a growing soil mixed with coarse sand. The cuttings only take root at temperatures above 22 degrees Celsius – in case of doubt you should therefore keep the Christstern cuttings in a special cultivation box or mini greenhouse with floor heating.
Picture gallery: Ideas with poinsettias
Diseases and pests
Yellowing or wilting leaves in poinsettias are usually the result of cold draughts. Permanently wet soil leads to root rot and grey mould. Cut off affected leaves immediately and remove them carefully so that the fungal spores cannot spread further. Aphids like to infest young shoots. Excessive air dryness can lead to wool and scale insects.
Whether potted plants such as oleanders or indoor plants such as orchids: The scale insect infests the most diverse plants. René Wadas, a herbalist, will give you his tips on pest prevention and control: Production: Folkert Siemens; Camera: Fabian Primsch; Editing: Dennis Fuhro; Photo: Flora Press/Thomas Lohrer
I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.