So with this warmer weather, the violets should grow bigger and better, right? Well.... that all depends. The excellent site from the folks at Optimara say that the ideal temperature for violets is between 65 and 75 degrees F. Other authorities say that the range is up to 80 degrees F. Most homes are generally kept about this warm and comfortable throughout the year. But, what happens when the temperature is either much higher or much lower than that?. Do the violets stop growing? Do they wilt? What happens exactly?
When the temperature is too high, above 80 degrees F., growth and flowering are slowed down. Injury to the leaves may occur. There can be burnt edges, lightening or "yellowing", variegates may start to go all white causing a lethal reaction. Without the green chlorophyll the leaf can not produce any food for itself and it will eventually die. Soil bacteria which activate the plant's ability to produce more chlorophyll are affected at these high temperatures. High temps. also can cause petiole elongation.
Temperature has a great effect on the "time" it takes for a plant to come into flower. The "amount" of light affects the numbers of flowers. It is estimated that 25 degrees C. is the best temp. for violets. That is 77 degrees F. (Click on the photo to see it larger.)
What happens when the violets are subjected to cold conditions? Cold temperatures slow root growth and plant growth. Moisture can now start to be problematic, because even a little excess moisture can lead to root rot. Flower size is diminished and so is leaf size. Roots are 50% less active at 15 degrees C. or 59 degrees F.
Another extremely interesting site posted by the University of Michigan from Dr. Royal Heins and his research assistants has a 100-plus image Power Point presentation about temperatures and gases and how it affects plant growth and metabolism. Our focus is on slides 91 and 92. These two pictures show a very interesting correlation between the temperature and the growth and size of the violet leaves. For easier comparison here are the conversions.
14 deg. C. = 57.2 deg. F.
18 deg. C. = 64.4 deg. F.
22 deg. C. = 71.6 deg. F.
26 deg. C. = 78.8 deg. F.
30 deg. C. = 86 deg. F.
The graphs are using temperature and the "Daily Light Integral", or how much light the plant is getting. From this we can compare what more light and higher temperatures do in respect to a violet plant. Please look at the rest of the slides.... although we aren't getting the audio portion of the presentation, we can really get some good information out of it. Also, note slide 67. It shows the effects of a plant when it's in proximity to a vent or other cold source.