Question
Hello Will,
I have 2 Calthea Mia. They are both in 6-inch pots. They both seem to be very healthy, very little brown edges & tips, good amount of new growth and one has a flower that has lasted almost 2 months. I make sure their soil is kept lightly moist and provide lots of humidity. They, like all my Caltheas and Prayer Plants are kept under artificial lighting. They are getting the proper light intensity (About 15-25 watts per square ft of growing space, which is proper for low light plants) and they get 16 hours of light a day. All of the other Caltheas, Prayer Plants and Stromanthes are doing very well under this system. All of my plant lights are on timers so they come on and go off at the same times everyday.
The problem is these 2 Calthea Mia do not open and fold up their leaves properly. They will fold up their leaves every day about 5-6 pm while it is still full light and they reopen their leaves around 3-4 am while it is dark.
I had one Mia before the other one and thought that it might be a problem with just that plant but after I got the other Mia it started doing the same thing shortly after I got it. Both Mias are together on the same plant stand under the same light. I thought maybe they were picking up light from a small nightlight in the hall and even as distant and dim as the light is, it maybe was triggering them to unfold
So I removed the light. After 2 weeks of no nightlight they were still doing the same thing. I have tried shortening their light time. I tried setting their light to come on about the time they open at 3-4 am and putting them in darkness when they fold up at 5-6 PM. After doing that for about 2 weeks I slowly started turning on their light on a little later and putting them in darkness a little later, trying to get them on a normal cycle but they stayed on their odd schedule no matter what I did.
I am stumped. I would appreciate any ideas you may have.
Thank you for your help.
Melina


Answer
Hi Melina,

Congratulations on your great success with your Marantas Calatheas, and Stromanthes. They are not easy plants to keep looking good, but you have obviously succeeded.

Your question is an unusual one because you perceive a problem where there is none. Certain species of Maranta are called "prayer plants" because of their proclivity to open and close with the daylight. Other plant species do this, as well. Some, but not all Calatheas and Stromanthes may open and close this way. Those that do not are not in any way defective.

Calathea Mia is a fairly recent hybrid that is noted for its unusual flower. Hybridizes often focus on flowering characteristics at the expense of other characteristics.

It is hard to know just why the Mia opens and close at the times your described. Once hybridizers start fooling with genetic composition it is difficult to predict what you are going to get.

Your Mia's have clearly demonstrated that they are genetically inclined to open at 3 AM and close 14 hours later. You have also demonstrated that altering the lighting will not change that. So I recommend that you accept this genetic predisposition and take satisfaction in knowing that your care results in a fine and healthy plant.

Please let me know if any of this is unclear or if you have any additional questions.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

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