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Plant Diseases of Poinsettias


Poinsettias are a holiday favorite but they do have a few problems.  Before we get to that, let’s talk about how to pick out the perfect plant.

Believe it or not, what we value about the poinsettia is not the bloom.  The “flowers” themselves are little yellow beads in the center of the colored leave.  The leave change colors due to the amount of sunlight or light in general they receive during their upbringing. 

Now that we have the basic idea of why we buy poinsettias, let learn how to pick the best one.

The first thing you need to look at is the “flowers” or yellow beads in the center of the colored leaves.  To get the biggest bang for your buck, you want your poinsettia to have closed beads.  If the flowers of the poinsettia are open, the quality of the poinsettia will be reduced.

The second thing you want to look for is the colored leaves (bracts) of the poinsettia.  What you want is a poinsettia that has bracts that have already changed.  While you may think that a little green mingled in with the pink or red is fine, it really is not if you want pure color on the top of your plant.  As stated before, this color change is brought on by a light and dark cycle that can be frustrating to replicate.  In doing so, the best approach is to pick one that is full of color on the top.

The last thing to look for is where plant diseases come into play and this is the health of the leaves.  If you find that your poinsettia has brown or dying leaves on the lower part of the stem, do not select this plant.  This can be an indication of improper watering, rough handling and/or plant disease.

Now that we know how to pick the best poinsettia, let’s take a look at some common plant diseases that poinsettia’s can suffer from.

One of the common problems poinsettias can suffer from is leaf drop.  This habit of plants dropping leaves is really nothing to worry about until it gets to the point of defoliation.  If it seems that you are picking up leaves everyday from your poinsettia then chances are you have leaf drop.  The cause for this can be root rot, overhead watering, not enough light and/or moisture.

To reduce the chances of developing this problem starts with your watering regimen.  The first thing you need to do is to either remove your plant from its foil sleeve or poke holes in the foil.  Either one of these approaches will allow the water to drain away from the plant. 

Once you have dealt with the decorative foil, the next step is watering.  A lot of problems poinsettias have come from improper watering or in this case, watering from the top.  Yes, I know you have watered from the top many times but the problem with this approach is it gets the leaves and stems wet.  If they do not dry quickly then you develop plant disease problems.  In doing so, the best approach is to place your potted poinsettia in a saucer.  Once that is done, add water to the saucer and allow the plant to take up water from its drainage holes into the soil. 

Allow the container to sit in the container until the soil surface feels moist.

Bacterial canker is another plant disease that can be brought on my improper watering.  How do you know if you have this issue?  Well, all you have to do is to take a look at the stems and leaves.  As far as the stems go, look for up and down water soaked streaks.  The leaves, on the other hand, will develop spots, which will lead to leaf loss.  If you find any of these symptoms, the best approach is to just throw the plant away. 

Scab is a unique plant disease that poinsettias can suffer from.  It is brought on by Sphaceloma poinsettiae.  This plant disease starts off as small spots that are light colored with yellow edges.  These spots will sit up around the veins of the leaves.  As the disease progress, the spots will elongate along the veins. 

If you find that you plant is suffering for this disease, the first thing you need to do is to reduce the humidity as much as possible.  Also, you will need to only water from the bottom.  Having said that, it will just be a matter of time before the disease kills the plant.

While not watering properly can cause several different problems, there are other plant diseases that are caused by reckless handling.  This includes Botrytis Stem Canker and Botrytis Flower Blight.  The signs of the first disease large cankers that are light brown form on older stems of the poinsettia.  As the canker continues to grow, it will eventually go all around the stem and girdle it.  Once that happens, the plant material about the canker will die because water and nutrients have been cut off.  To prevent this problem is simple and starts when you first purchase your plant.  When carrying it around make sure to protect the stems of the plant.  After you get it home, gently remove any coverings that may be around the plant.  This includes the plastic bag around the plant and the decorative foil wrapper around the pot. 

Whilst the plant disease discussed above attacks the stems, the latter poinsettia disease effects everything, which includes flowers, leaves, and stems.  As you can imagine, this plant disease is caused by damage to the plant material.  To prevent it, follow the same handling tips described above.

Although poinsettias do have a few problems, most of them can be taken care of with a little plant TLC but………….if you find that you do have one of these problems and the situation is not getting better, do not hesitate to dispose of the plant in the trash.  The best part of this plant is the fact that it is an inexpensive addition to the holiday season and most people only purchase them to be a disposable decoration instead of a long term investment. 

So sit down, enjoy the season and do not sweat poinsettia plant disease.  You will always be able to buy another one next year.  


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