Frost will not form on a steep hill... the cold air moves down and creates enough "wind' to prevents the frost from forming. Here is a photo of two plants that were in 30 f for about six hours two days ago... wish I could get closer during the day for some really nice photos. http://forum.grasscity.com/photopost/showphoto.php?photo=97672&title=compost-1&cat=500
Don;t forget that Mulching will also help keep the soil/roots warmer. A VERY important part of frost resistance. 2 inches deep applied all round the base of the plant will help a LOT
found some interesting info today: Ed Rosenthal's Grow Tips Maintaining Optimum Grow Room Temperature Marijuana plants are very hardy and survive over a wide range of temperatures. They can withstand extremely hot weather - up to 120 degrees - as long as they have adequate supplies of water. Cannabis seedlings regularly survive light frost at the beginning of the season. Both excessively high and low temperatures can slow marijuana's rate of metabolism and growth. The plants function best in moderate temperatures - between 60 and 85 degrees. As more light is made available, the ideal temperature for normal plant growth increases. In high temperature and moderate light conditions, the plant's stems elongate. Strong light and low temperature conditions will decrease stem elongation. During periods of low light, sem elongation can be decreased by lowering the temperature. Temperatures below 50 degrees slow growth in most varieties of marijuana. When the temperature drops below 40 degrees, the plants may experience some damage and require about 24 hours to resume growth. Low nighttime temperatures may delay or prevent bud maturation. Some equatorial varieties stop growth after a few 40 degree nights. Marijuana is low-temperature tolerant. Outdoors, seedlings sometimes pierce snow cover, and older plants can withstand short, light frosts. Statistically, more males develop in cold temperatures. Low temperatures, however, slow down the rate of plant metabolism. Cold floors can lower the temperature in containers, thereby lowering root temperature and slowing germination and plant growth. Ideally, the medium temperature should be 70 degrees.
Im in PA and I have a plant I LST'd in a 5 gal bucket. It has buds and some snow on them but they dont seem to be changing much. I just brought it in tonight to get it out of the frost. It is a sativa (bagseed) and it doesnt seem to be bothered by the cold. I will keep checking it closely and I hope that it will finish growing those buds! Some fan leaves are beggining to turn yellow. Is that because the cold weather or the natural occurance of the plant in flowering stage?