Some opinion with respect to garden plants
1) iSpot is intended for organisms in the wild - so strictly speaking no zoo animals, no pets, no farm animals, no crop plants, no cultivated plants in gardens, or house plants, no aquarium fish, no street trees, no amenity shrubs or bulb plantings, no game bird cover or food plants, ... (I don't consider single species hedgerows to be recordable, or the dominant species in a hedgerow that has been invaded by other species.)
2) But we don't want to discourage the newbies by telling them off for putting up observations of garden plants
3) The worse offenders for putting up garden plants are people doing OU courses, so it appears that the OU are less bothered than some of the regulars here
4) There is a case for putting up cultivated plants as examplars for plants that might be encountered in wild - see my Crocus Project (a mixture of naturalised and cultivated observations) for an example which got some positive feedback from some regulars.
5) The line between cultivated and spontaneous plants can be hard to discern - there is even a category of garden edge plants, which are found predominantly in gardens, but in contexts where they appear either spontaneous or naturalised rather than planted.
6) If cultivated plants are to be added they should be clearly marked as such.
7) To use the interaction feature for insects feeding/nectaring on garden plants requires adding observations for the garden plants.