There is a botanical garden in San Antonio, Texas, that spreads across a spacious area. We arrived in the morning, and entered through an older building, certainly from another century. The fee is nominal, just $12 general admission, and $2 less for seniors, military personnel, and children. They had no restriction on photographs, which was a real plus.
Nearby is a Japanese Tea Garden, which does have a fee for photography. But, I believe it is free to enter. We had too little time to go to both.
It was a hot day, but the garden is arranged with much tree cover, so shade is easily found. And there are ample benches for those in need of resting. We arrived in a period where temperatures in the afternoon soared to over one hundred degrees Fahrenheit, and it was a prolonged period of over a week for such an occurrence. It was also during a dry spell, and concern of drought conditions were being heard on the news.