Where to find info on maxiimum temp tolerated by various plants
I am gardening near Lake Mathis in South Texas. Every day with clear sky in August runs well over 100 deg F, yesterday was 111F in the shade just outside the kitchen door! Seeds are not germinating at all under a big carport awning...but I need to get seeds started for fall vegetables. (the carport awning area stays a bit cooler, around 4 deg. or so so---- it probably hit 107 yesterday) Even though mulched heavily now, most of my (all young) fruit trees are dying (low-chill peach and plum and a Satsuma). Only a Quince and two apple varieties are still growing. All the bamboo seedlings in pots under the carport have died.
Although it is easy to find the lowest temp a plant or tree can take in winter, it is not very often that an internet article tells you what the max temp is that it can take. The growing zone designations are too general, especially when you live in a place with such high summer temps! So I was wondering if there is some database of plants/trees that gives MAX temp tolerated? Then I would know what plants are a waste of time and money here.
Also I have heard that although canteloupe like full sun, in very hot climate/summers, they benefit from partial shade. So I am wondering if the problem with the fruit trees could be that they need some partial shade (problematic to provide....there are no full-grown trees anywhere around to provide any shade) Thanks to all.