I am having difficulty growing summer squash. The leaves are full and green, but as soon as the squash starts growing, they become black and wither. Is it the soil? or , perhaps a pest? Can anyone advise?
you need bees, your squash is not getting pollinated a fix is to buy some mason bees or every time you see 2 flowers grab a q-tip/small soft paint brush and rub it around each one and then back to the first one to help it pollinate and put on fruit.
If the problem is due to pollination, then you can self-pollinate like Stephanie said. If you need bees the easiest way (as I have done) is to plant several hyssop plants around the edge of your garden. Bees swarm all over these plants and the plants grow fast in one season and is perennial. they are a very attractive plant (herb). The next thing that could be the problem is blossom end rot (BER) and that usually happens when there is not enough calcium in the soil. you can correct this by first taking a soil sample. Add lime to the soil as needed, potash (potassium) you can use wood ash for this as well as compost. a lack of phosphorus is another that can cause this problem. this strengthens the root system and is needed to improve flowering which means more fruit and more seed. for this you can use some bonemeal, & cottonseed meal. I usually put 2 tbls of this in the planting hole when I transplant. Epson salt is another good thing I use to prevent BER. you can use a tbls of this mixed in with the bonemeal and cottonseed meal in the planting hole. I also mix 2 tbls of Epson salt in a spray bottle and when the squash (or tomato) blooms first appear I spray this solution lightly on the blossoms. BER is a pretty common thing and has happen to us all mostly at sometime. Since your plants leaves are pretty and green, you have no nitrogen problem it appears. hope this helps you as all of the above suggestions also.