Christmas plants: 15 myths checked

Daniel Platteau

In short: no, the poinsettia is not deadly; its red "flowers" are leaves; and it can flower again if you give it long nights. A holly without berries is often a male, or a female with no male nearby. Mistletoe weakens a tree without necessarily killing it, rarely grows on oak, and its leaves are more toxic than its berries. The Christmas cactus comes from the humid forests of Brazil, not the desert. As for the tree, an artificial one is only greener if it is used for a great many years, and many "firs" are actually spruces. Here are fifteen myths, checked one by one.

Every year the same phrases come back in garden centres and around the table: "careful, it's deadly", "it'll never flower again", "mistletoe kills trees". Some are false, some half true, a few right for the wrong reasons. We checked them against reference sources: poison centres, published studies, the Royal Horticultural Society (RHS) and Kew Gardens.

The poinsettia

The poinsettia, Euphorbia pulcherrima, is native to Mexico and Central America, as far as Guatemala (RHS, n.d.-b). In the wild it is a shrub of around 3 metres. It is named after Joel Roberts Poinsett, then the United States ambassador to Mexico, who reportedly introduced it to the US in the late 1820s (Evens & Stellpflug, 2012).

1. "The poinsettia is deadly"

False. This is the most stubborn myth, and it rests on a single story: the death of a two-year-old in Hawaii in 1919, blamed on a poinsettia leaf but never confirmed (Evens & Stellpflug, 2012).

The data say something quite different. A team from the Pittsburgh Poison Center analysed 22,793 cases of poinsettia exposure reported to US poison centres between 1985 and 1992, almost all of them children. The result: no deaths, 92.4% of people with no symptoms at all, and 96.1% managed without going to a hospital (Krenzelok et al., 1996). According to the POISINDEX toxicology database, quoted by Colorado State University, a 23 kg child would have to eat more than 500 bracts to develop symptoms (Newman et al., 2025).

That does not make the poinsettia a snack. Its milky sap is irritating: a chewed leaf can give a child a mildly upset stomach, and a dog or cat that chews several leaves may drool and vomit (Anses, 2020). The poinsettia also belongs to the same family as the rubber tree: around 40% of people allergic to latex also react to its sap (Evens & Stellpflug, 2012). Wear gloves when you prune it.

2. "Its big red flowers"

False. The big red, pink or cream "petals" are bracts, modified leaves that change colour. The real flowers are the small yellow buttons in the centre, called cyathia (RHS, n.d.-a).

This detail is useful when buying: choose a poinsettia whose cyathia are still closed or only just opening. A plant whose little yellow flowers have dropped is at the end of its flowering, and its bracts will not last long (Mississippi State University Extension, 2023).

3. "It needs warmth, right by the radiator"

False. The poinsettia is a tropical plant, but it hates extremes. The RHS recommends a steady temperature of around 16 to 21 °C, bright light out of direct sun, and compost that is just moist. It dislikes the hot, dry air of a radiator, cold draughts, and a chilly windowsill at night (RHS, n.d.-a).

Cold is its real enemy, and it often strikes before the plant even gets home. The RHS advises against poinsettias displayed on the pavement or in a cold shop: a few hours of chill are enough for the bracts to drop within days (RHS, n.d.-a). In a Belgian winter, have it wrapped for the journey and unwrap it as soon as you get in.

4. "It never flowers again"

False, but it takes effort. The poinsettia is a short-day plant: like the chrysanthemum, it forms its coloured bracts when the nights get long. In a living room lit every evening, it never gets the signal.

The method from Colorado State University (Newman et al., 2025):

late March or April: cut the stems back, leaving three or four leaves on each, then repot in late spring;
in summer: put it outside in light shade once nights stay above 13 °C, and pinch it regularly until the end of August;
from 1 October: give it at least 14 hours of complete darkness every night (an opaque box or a cupboard), at 16-21 °C, until the bracts colour up, around late November.

The slightest stray light (a lamp, a street light) delays or stops flowering. That is also why a grow light should never shine on a poinsettia at night in autumn. Single-stem plants rebloom poorly (Mississippi State University Extension, 2023). For many people, buying a new poinsettia each year is simpler, but success is possible.

Holly

Common holly, Ilex aquifolium, is native to Belgium. It is an evergreen shrub or small tree that flowers in May and June.

5. "Every holly has red berries"

False. Holly is dioecious: each plant is either male or female. Only females bear berries, and only if a male holly flowers nearby to pollinate them (RHS, n.d.-c; RHS Plants, n.d.). A holly that has never had berries is therefore often a male, or an isolated female.

A classic trap: variety names are misleading. 'Golden King' is a female and 'Silver Queen' a male (RHS, n.d.-c). Before buying, check the sex on the label (often marked f or m) and, if you want berries, add a male if there is no holly in the neighbourhood.

6. "All holly leaves are prickly"

False. Look at an old holly: high up, many leaves are smooth. Spanish researchers studied 40 hollies in south-eastern Spain: 39 carried both prickly and smooth leaves. Prickly leaves were linked to browsing by deer and goats and dominated the lower part of the tree, within reach of their teeth; the same tree produces both forms through epigenetic changes, without any change to its DNA sequence (Herrera & Bazaga, 2013). In other words, holly only "spends" on prickles where it needs them.

7. "A single holly berry can kill a child"

Exaggerated, but take it seriously. Holly berries are toxic. According to Anses, the French health safety agency, swallowing one or two berries usually causes nothing, or a mild stomach upset. Larger amounts can cause heavy drooling, repeated vomiting and diarrhoea, drowsiness and even convulsions. The tough, prickly leaves are rarely involved (Anses, 2020). French poison centres receive 60 to 80 calls a year about children who have put holly berries in their mouths, nearly 40% of them over the holidays (Anses, 2020).

Mistletoe

European mistletoe, Viscum album, forms the green balls so visible in bare trees in winter. Its sticky seeds are spread by birds, which leave them on branches (Thomas et al., 2022).

8. "Mistletoe is a parasite that kills the tree"

Half true. Mistletoe is a hemiparasite: its green leaves photosynthesise, but its sinkers inside the branch take water and minerals from the tree, and probably some of its sugars too. One or two plants do not threaten a healthy tree. A heavy infestation, however, weakens the host, because mistletoe uses a lot of water; more than 700 mistletoe plants have been counted on a single tree (Thomas et al., 2022).

9. "Mistletoe grows on oaks"

Rarely. The image of the druid cutting mistletoe from an oak with a golden sickle comes from an account by Pliny the Elder, which may be invented (Briggs, 2021). If oak mistletoe was sacred, it was precisely because it was rare. In Britain, only ten to twenty oaks are known to carry mistletoe (Box, 2019).

In Belgium, mistletoe grows mostly on hybrid poplars and apple trees. In Limburg, a study published in 2021 found more than 80% of mistletoe plants on poplars, about 15% on apple trees and 5% on false acacias; limes, hawthorns, willows and maples are occasional hosts. Mistletoe was long thought to be limited to the chalky soils of the south and centre of the country: the authors show that what matters is the calcium content of the host tree, and that mistletoe is spreading in Flemish Brabant and both Flanders provinces (Berten et al., 2021).

10. "It's the mistletoe berries that are dangerous"

False, it's mainly the leaves. In European mistletoe, the leaves are more toxic than the white berries (Anses, 2020; Evens & Stellpflug, 2012). A few berries swallowed by a child usually cause nothing, or a mild stomach upset; large amounts can cause heart rhythm problems, low blood pressure or drowsiness. Mistletoe can be fatal to animals, pets and livestock alike (Anses, 2020). The only two human deaths found over 25 years by a medical review involved people who had drunk mistletoe tea (Evens & Stellpflug, 2012).

Beware of reassuring articles from the United States: the studies there that conclude mistletoe is not very toxic are about American mistletoe, Phoradendron, a different plant that is less toxic than our Viscum album (Evens & Stellpflug, 2012).

The Christmas cactus

11. "It's a desert cactus that barely needs water"

False. The Christmas cactus (Schlumbergera) is indeed a cactus, but an epiphytic one from the humid forests of south-eastern Brazil, where it grows on tree branches (POWO, n.d.; RHS, n.d.-d). It wants neither full sun nor long droughts: bright but indirect light (an east-facing window is ideal), compost kept moist from April to September without ever being waterlogged, and never below 10 °C (RHS, n.d.-d).

In shops you mainly find Schlumbergera truncata and the hybrid S. × buckleyi, in many varieties (RHS, n.d.-d).

12. "To make it flower, just put it somewhere cold"

False, it's more subtle than that. Like the poinsettia, the Christmas cactus forms its buds when the days shorten and the nights cool down. The RHS recommends two rest periods a year, at 12-15 °C with less watering: from mid-September until buds appear, then from late January to late March. A lamp switched on near the plant in the evening can be enough to prevent flowering (RHS, n.d.-d).

Once buds have formed, move it back to 18-20 °C and leave it alone: temperature swings, cold draughts (in the shop or on the way home) and overwatering make the buds drop (RHS, n.d.-d).

The Christmas tree

In Belgium, the Christmas tree is an Ardennes business: the country produces about 3 to 3.2 million trees a year, of which only some 700,000 stay on the Belgian market (Paperjam, n.d.).

13. "An artificial tree is greener because you keep it"

False in most cases. In 2009 the Canadian consultancy Ellipsos compared the full life cycle of a real tree bought every year with an artificial tree made in China and kept for six years. For the climate, the artificial tree did more than one and a half times worse; it would have had to be kept for about twenty years to break even (Bowyer et al., 2018). A US study from 2010 found a lower threshold, of 4 to 9 years depending on the assumptions. Both show that the distance driven to fetch the real tree weighs heavily in the result (Bowyer et al., 2018).

The other myth, "buying a real tree destroys forests", is also false: Christmas trees are grown in plantations, like a crop. Growing them is not impact-free (weeding, water, soil), and researchers in Gembloux are working on alternatives to chemical herbicides (RTBF, 2025b). Either way, the difference is small: according to Ellipsos, the impact of one tree, real or artificial, is offset by leaving the car at home for one to three weeks a year (Ellipsos, 2008). The most sober choice: a real tree grown close to home, or an artificial one you already own and keep for as long as possible.

14. "A Christmas tree is a fir"

Not always. The traditional Norway spruce (Picea abies) is not a fir (Abies). The Nordmann fir (Abies nordmanniana), now the favourite, is one; it comes from Turkey and the Caucasus (RTBF, 2025a). To tell them apart (RTBF, 2025a):

	Fir (Abies, including Nordmann)	Spruce (Picea)
Needles	flat	rather cylindrical or angular
Twig without needles	smooth, with round scars	rough, each needle grew on a small peg
Cones	upright, break up on the tree	hanging, fall whole

You can also tell in the living room: spruce smells lovely but drops its needles quickly, while the Nordmann keeps them for a very long time (RHS, n.d.-e). The Douglas fir, sometimes sold as a "fir", is neither a fir nor a spruce (RTBF, 2025a).

15. "Plant a potted tree in the garden and it will grow back"

Only if it really grew in its pot, and was not cooked indoors. The RHS distinguishes container-grown trees, which have always lived in their pot, from containerised trees, dug up and put into pots, which lost part of their roots when they were lifted (RHS, n.d.-e). Ask which one you are buying.

To give it a chance, the RHS advises bringing it in as late as possible, keeping it in a cool room away from radiators, and not leaving it indoors for more than twelve days. Afterwards, plant it in the garden or repot it into a bigger container. A tree kept in a pot often lives only a few years (RHS, n.d.-e). And think about its adult size: a Nordmann planted in front of the window becomes a big tree.

In the Ardennes, potted trees account for only 4 to 5% of production. In late 2025 a local mayor accused this crop of impoverishing fields by carrying topsoil away in the pots; according to RTBF, the claim needs strong qualification, since the main producer mostly uses bought-in growing medium (RTBF, 2025c).

What about the amaryllis?

The other great Christmas plant has its own article: how to plant it for Christmas and get it to flower again the following year. Just remember that it is not harmless to cats and dogs, and that it reflowers easily if you let it rebuild its reserves.

If something is swallowed

These first-aid steps are those recommended by Anses (2020); the number is that of the Belgian Poison Centre (DH, 2020).

Summary table

Myth	Verdict
The poinsettia is deadly	False: no deaths in nearly 23,000 cases studied; irritating sap
Its flowers are red	False: those are bracts, the flowers are the yellow buttons
It loves radiator warmth	False: 16-21 °C, neither hot and dry nor cold draughts
It never flowers again	False: 14 h of darkness a night from October
Every holly has berries	False: only females, with a male nearby
All holly leaves are prickly	False: upper leaves are often smooth
One holly berry can kill	Exaggerated: 1 or 2 berries, few or no symptoms; more is serious
Mistletoe kills the tree	Half true: it weakens it when abundant
Mistletoe grows on oak	Rarely: mostly poplars and apple trees in Belgium
Mistletoe berries are the danger	False: the leaves are more toxic
The Christmas cactus is from the desert	False: an epiphyte from the humid forests of Brazil
Cold alone makes it flower	False: long, cool nights, and don't move it
An artificial tree is greener	False, unless it lasts a very long time
A Christmas tree is a fir	Not always: spruce is not a fir
A potted tree can always be replanted	Only if it grew in its pot and spent little time in the warm

Test yourself

Sources

Anses. (2020, 15 December). Plantes décoratives : leur ingestion peut être toxique pour les hommes et les animaux. https://www.anses.fr/fr/actualite/plantes-decoratives-leur-ingestion-peut-etre-toxique-hommes-animaux

Berten, R., Neyens, T., Willems, T., & Vangronsveld, J. (2021). Is Viscum album gebonden aan kalkrijke bodems? Dumortiera, 117, 3-10. https://zenodo.org/records/4541000

Bowyer, J., Groot, H., Erickson, G., Henderson, C., Pepke, E., Howe, J., & Fernholz, K. (2018). Environmental assessment of natural vs. artificial Christmas trees. Dovetail Partners. https://dovetailinc.org/upload/tmp/1579550365.pdf

Box, J. (2019). Oaks (Quercus spp.) parasitised by mistletoe Viscum album (Santalaceae) in Britain. British & Irish Botany, 1(1), 39-49. https://britishandirishbotany.org/index.php/bib/article/download/7/11

Briggs, J. (2021). Mistletoe, Viscum album (Santalaceae), in Britain and Ireland; a discussion and review of current status and trends. British & Irish Botany, 3(4), 419-454. https://doi.org/10.33928/bib.2021.03.419

DH. (2020, 30 December). Poinsettia, houx, gui : gare aux intoxications dues aux « plantes des fêtes ». https://www.dhnet.be/conso/consommation/2020/12/30/poinsettia-houx-gui-gare-aux-intoxications-dues-aux-plantes-des-fetes-X5M2RXU5DVCVXF252H6SAQ3XCM/

Ellipsos. (2008, 16 December). Christmas tree life cycle analyzed [Press release]. Woodworking Network. https://www.woodworkingnetwork.com/news/press-releases/christmas-tree-life-cycle-analyzed

Evens, Z. N., & Stellpflug, S. J. (2012). Holiday plants with toxic misconceptions. Western Journal of Emergency Medicine, 13(6), 538-542. https://doi.org/10.5811/westjem.2012.8.12572

Herrera, C. M., & Bazaga, P. (2013). Epigenetic correlates of plant phenotypic plasticity: DNA methylation differs between prickly and nonprickly leaves in heterophyllous Ilex aquifolium (Aquifoliaceae) trees. Botanical Journal of the Linnean Society, 171(3), 441-452. https://doi.org/10.1111/boj.12007

Krenzelok, E. P., Jacobsen, T. D., & Aronis, J. M. (1996). Poinsettia exposures have good outcomes… just as we thought. American Journal of Emergency Medicine, 14(7), 671-674. https://doi.org/10.1016/S0735-6757(96)90086-8

Mississippi State University Extension. (2023). Selecting and maintaining poinsettias (Publication 2573). https://extension.msstate.edu/publications/selecting-and-maintaining-poinsettias

Newman, S. E., Edmunds, B. A., & Goldsberry, K. L. (2025). Selecting and planting poinsettias. Colorado State University Extension. https://extension.colostate.edu/?p=3114

Paperjam. (n.d.). Mon beau sapin, roi du business. https://paperjam.lu/article/mon-beau-sapin-roi-business

POWO. (n.d.). Schlumbergera truncata (Haw.) Moran. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:229597-2

Royal Horticultural Society. (n.d.-a). Poinsettias. RHS. https://www.rhs.org.uk/plants/euphorbia/poinsettia

Royal Horticultural Society. (n.d.-b). Euphorbia pulcherrima (Plant profile). RHS. https://www.rhs.org.uk/plants/88057/euphorbia-pulcherrima/details

Royal Horticultural Society. (n.d.-c). Hollies. RHS. https://www.rhs.org.uk/plants/hollies

Royal Horticultural Society. (n.d.-d). How to grow Christmas cactus. RHS. https://www.rhs.org.uk/plants/christmas-cactus/growing-guide

Royal Horticultural Society. (n.d.-e). Christmas trees: types and care. RHS. https://www.rhs.org.uk/advice/profile?pid=374

RHS Plants. (n.d.). Ilex × altaclerensis 'Golden King'. https://www.rhsplants.co.uk/plants/_/ilex--altaclerensis-golden-king/classid.4029/sku.pl00080043

RTBF. (2025a, 24 December). Votre « sapin » de Noël n'est peut-être pas un sapin, voici pourquoi. https://www.rtbf.be/article/votre-sapin-de-noel-n-est-peut-etre-pas-un-sapin-voici-pourquoi-11652128

RTBF. (2025b, 17 December). Des chercheurs de Gembloux développent une alternative aux herbicides chimiques pour les sapins de Noël. https://www.rtbf.be/article/des-chercheurs-de-gembloux-developpent-une-alternative-aux-herbicides-chimiques-pour-les-sapins-de-noel-11650108

RTBF. (2025c, 18 November). Les sapins de Noël en pot, un désastre pour l'Ardenne belge ? https://www.rtbf.be/article/les-sapins-de-noel-en-pot-un-desastre-pour-l-ardenne-belge-11633782

Thomas, P. A., Dering, M., Giertych, M. J., Iszkuło, G., Tomaszewski, D., & Briggs, J. (2022). Biological Flora of Britain and Ireland: Viscum album. Journal of Ecology, 111(3), 701-739. https://doi.org/10.1111/1365-2745.14036