Here in the South, transplanting a delicate tomato or fig plant into a standard, black industry pot can often spell doom for the tender young plant. If that black pot is placed in direct sunlight for a significant amount of time, it can dry out really quickly. I’ve had to water 5 gallon buckets with plants in them twice a day in the heat of summer. How much more a tiny 1 gallon pot baking in the sun?
But there’s more danger in such a small pot – excessive heat. Some plants do not tolerate soil temperature fluctuation or high temps. It is easy to cook your plants to death. I decided to paint some of my pots to reflect some of the solar energy that dark colors absorb. Since I have a thermometer, I measured the results.
Its far from scientific, and I had only two examples each of black and light pots. Each was filled with pre-moistened growing media and placed in direct morning sunlight for half a day. I used an instant food thermometer that has proven to be very accurate, and took multiple readings from each pot. I measured the temperature in the middle of the pot and within 1 inch of the edge.
Here the soil in the middle of the back pots hovers around 92.
However, near the edge it gets up to 114. My other pot, which I failed to photograph, broke 124 degrees.
The painted pots are about an 80% in value on a scale from black (0%) to white (100%). There is an average 15 degree difference between the two pots when temperatures are measured near the edge of the soil. The lighter color makes a relatively big difference and may preserve plants from heat stress. There was little difference in temperatures when measure in the middle of all pots.
If you cannot find white pots, paint is a cheap alternative. I used latex indoor house pain that we had lying around. The pots will chip and peel, but I can easily re-paint the next time I use them.
If you have similar experiences or better ideas, please comment.