The atmospheric chemistry would be upset by cutting out sunlight. It would be like a nuclear winter and could last for tens of thousands of years. These comets are 200-300km (186 miles) in diameter they are sheer monsters and could sterilise the earth if we are hit by one.
Heat stress â Another reason for rose leaves turning yellow is the rose bush is under some sort of stress. A common cause of stress is heat stress. The rose bush turns yellow and drops its foliage in an effort to cool down in the case of heat stress.
Reasons Gardenia Leaves Turn Yellow. The first thing you should do if your gardenia's leaves begin to yellow is have some of the plant's soil tested at your local nursery. This will reveal any possible nutritional deficiencies that could cause this problem. Here are some of the most common reasons for the yellowing.