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Poinsettia - are they just for Christmas?

Poinsettias can provide that vivid splash of colour just when needed in the depth of winter but, if you are unlucky, a plant bought just before Christmas has shed most of its leaves or even collapsed by New Year's Day. But is it chance which decides how long your plant lasts?

Admittedly it is often difficult to find an indoor spot which meets all the requirements listed on the plant label - enough light but not too much, no draughts, warm night and day but not too hot, not near radiators etc. So does it matter where you put them? What can you do to make sure your plant lasts well into the New Year?

Test details

Two days before Christmas Day (1999), medium sized poinsettias (about 30 - 40 cm/12 - 16 in high) were bought from three retailers (M&S, B&Q, Wyevale) and direct from a nursery. Some plants from each source were kept on a table near a west-facing window in a warm centrally-heated room (temperature range 19 - 22 degrees C, relative humidity 40 - 77) and others in a greenhouse (13 - 23 degrees C, 59 - 75 RH) with 12 hours supplemented light. Plant containers were placed in large trays and leaves falling from each plant into the tray were collected every two weeks, dried and weighed.

At the start of the trial a typical plant from each source was sacrificed and the total dry weight of leaves measured. To show the amount of leaves lost we expressed the weight of leaves lost every two weeks with the starting weight of the typical plant.

Some queries to ponder
  1. Do you think that the price you pay for a plant determines the size of the plant you get?
  2. Would you expect any of the plants, kept either indoors or in the greenhouse, to keep all their leaves into the New Year?
  3. Do you think plants would lose more leaves soon after purchase or later say after 6 weeks?
  4. Which plants do think would lose most leaves, those in the greenhouse or those indoors, the M&S, B&Q, Wyevale or Nursery sourced plants?
Results after two weeks

Price related to plant size

plant dry weight price per plant (GBP) cost per 10 gms dry weight (GBP)
Wyevale 09.7 gms 2.99 3.08
M&S 10.3 gms 4.99 5.14
B&Q 11.4 gms 2.99 2.62
Nursery 13.3 gms 4.00 3.01

All plants were reasonable size and looked healthy with dark green leaves and bright red bracts.

The Nursery plants carried the largest bracts and the largest and darkest green leaves. The cyathia (flowers) were brightly coloured on all plants.

The M&S plants were the most expensive.

Two M&S plants lost less than 1% of their leaves while one Wyevale plant lost 60%. Indoor plants lost much more leaf than the Greenhouse plants during this initial two week period. In the Greenhouse the M&S and the Nursery plants lost less than 5% on average.

Table

Results after four weeks

Table

After a 12% average leaf loss for all plants in the trial in the first two weeks the loss was only 3.5% in the second two weeks.

All Indoor plants continued to lose leaf more rapidly than the Greenhouse plants.

Results after six weeks

Table

The Indoor Nursery plants suddenly lost most leaves (around 20%) during the fifth and sixth week of the trial.

At the end of the six weeks the M&S plants had retained most leaves (average of 82.5% overall, 72% indoors and 93% in the Greenhouse.

Results after eight weeks

Table

A heavy loss of leaf by the Indoor Nursery plants brought the average Indoor plant loss to over 40% and left the M&S plants with, on average, the lowest leaf loss over the eight week period (33% Indoors and 9% in the Greenhouse)

Conclusions and some practical tips

As might be expected poinsettias, kept indoors in warm dry conditions with no special lighting typical of many conditions found in homes over the Christmas period, are likely to lose a third to a half of their leaves over a period of two months.

Some plants seem to lose their leaves quickly at an early stage while others can lose them later:

M&S: weeks 1-2 17, weeks 3-4 6, weeks 5-6 5, weeks 7-8 5

Nursery: weeks 1-2 9, weeks 3-4 10, weeks 5-6 19, weeks 7-8 17,

If a poinsettia is kept in conditions suitable for growing plants and properly looked after it should retain most of its dark green leaves and keep its bright coloured bracts and flowers for several weeks.

Tips:

  1. Don't buy plants on price - look for a quality plant.
  2. Choose plants with dark green leaves and brightly coloured bracts, commonly red, but above all check the very small flower in the centre of the bracts which should be coloured bright red/yellow/green. These flowers tend to turn brown or black if the plant is kept in adverse conditions. NB: labels appear to confuse or poorly explain the difference between the dark green leaves, the brightly coloured bracts (sometimes implied as being the flower) and the very small real flowers (known as cyathia).
  3. Buy plants which have not been kept in sleeves (not liked by the plant over long periods). But get plants protected by sleeves for transport home. Avoid exposure of plants to very cold wind, rain etc on the way home.
  4. Try keeping a group of plants close together so that they protect each other from dry or cold draughts.
  5. Above all keep poinsettias well away from central heating pipes and radiators.
Postscript

Reading the label taken from a good quality Poinsettia bought just before Christmas 1999 shows the difficulties both horticultural and linguistic:

'Light: Favours a light position avoiding too near a window' - so how do you decide where to place the plant?

'Feeding is not necessary during winter, but beneficial during growing period' - is the plant growing when kept indoors in reasonable light or not? It is quite possible that some feeding of plants bought at Christmas will help a plant to maintain good condition.

'Temperature: Will not tolerate temperatures, preferring 15-20c(65-70F)' - presumably this means extreme temperatures but try keeping to these temperatures day and night!

It is not usually worth trying to keep a Poinsettia plant going through the summer but it may depend on where you live and whether the local climate is of any help! It may be easier to buy a replacement plant. If you can find a warm location for the plant away from extremes of heat, especially cold nights, you may be able to keep the plant going - professionally grown plants are often kept short and compact by using a plant growth regulator and you therefore may find the plant grows longer stems and may be less attractive as a house plant.

The usual advice to keep the plant for the following winter is:

  • during late winter early spring minimise wtering and keep plant at around 10 to 15 degrees C
  • after the leaves have dropped, cut back the stems by at least half, apply minimal water
  • repot in early summer in a gritty loam/organic mix, keep in bright light at up to 18/20 degrees C
  • feed and water according to amount of new growth in summer and autumn
  • the plant needs 12 hours darkness to initiate flowering

 


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