I have not been able to find a guide (I am probably overlooking it somewhere) that explains what level of pests to expect at what challenge level of plant. I was quite surprised to discover my trumpet vine (plain variety, not silver or anything -- challenge level only 4) getting a rank 5 pest. I would have expected only the highest levels (6 and 7) to get that kind of pest, so I was trying to sort out the hows and whys so I don't get caught out again, having to watch the poor plant die because I don't have 25,000 gold yet.
Would someone please point me in the right direction?
First link, use to find pests. Hit section 2.5, pests, to go to the section about pests. Second link, to the Trumpet Vine page. Third link, to the Garden Imp, rank 5 pest, page. Fourth link, to the treasure card that prevents all rank 5 pests and below. Fifth link, a link to all seeds you can garden.
Hope I helped! I suggest knowing what you will deal with before you plant it, unless you are dedicating to wiki.