depends how deep you want to learn it. If it is just to improve skills in looking after your plants, I suggest to google not for Botany but Gardening with the t

depends how deep you want to learn it. If it is just to improve skills in looking after your plants, I suggest to google not for Botany but Gardening with the topic you are interested in (eg "gardening ph basics") If you really want to learn it thoroughly,look for the printed manual for plant physiology and biochemistry. But that will be boring (if you are not a real science freak).