Uli said: "The difficulty I have with the black pots is that they become too dry and too hot in my climate during summer so I have to move the pots to a shady place." This effect can be controlled in other ways because it results from very specific causes: High sun during mid-day will not cause the problem because the sun will not heat the plastic since it only impinges on it tangentially. It is only sunlight originating from near the horizon that is dangerous because it can effectively heat a large area of the pot by impinging at a perpendicular angle. At my latitude (40 degrees N) this will happen mornings on the east to northeast side in the summer and especially evenings on the west to northwest side. In the winter the same thing can happen on the south side at high latitudes. This is the main reason temperate fruit growers prefer to plant orchards on northern slopes as this tends to reduce sunscald ( https://en.wikipedia.org/wiki/Sun_scald/ ). But there is an additional aggravating effect that is strongest on air porous potting media, especially after watering - the heat pipe effect ( https://en.wikipedia.org/wiki/Heat_pipe/ ). Water is evaporated by the sun's energy captured by the black surface and the water vapor diffuses until it condenses on a cooler surface - the potting media near the heated side of the pot. Here it condenses and releases water's incredibly high heat of vaporization, heating the media far better than pure conduction ever could. Initially I thought of using a white sunshield but that is not as important as 'decoupling' the heated plastic from the potting media. One way to do this is a pot within pot scheme. Two same size pots might work marginally but not as well as e.g. a 3 gallon pot inside a 5 gallon pot. Also, in a cluster of pots, only the ones exposed on the offending side will be affected as they shade the others. If you want to prove this, plant a large black pot with a number of small plants and watch the ones on the (for me) northwest side die in summer while the others thrive. Tim _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/… Unsubscribe: <mailto:pbs-unsubscribe@lists.pacificbulbsociety.net>