In the garden it is normally a simple matter to define what is meant by a tree, a shrub, herbaceous perennials, annuals, climbers, creepers, ground covers, water or bog plants, even cacti and succulents. Yet when we come to indoor gardening we find that the range of plants we can grow includes all of these. We are limited only by size. So when we talk about house plants we can, in the widest sense, mean any plants of any kinds.
This is, of course, stretching the definition to its farthest range and although it gives some idea of the scope of house plants and the activity of indoor gardening, it will be more helpful to be somewhat more precise.
On the other hand, largely as a result of selection and breeding on the house plant nurseries, the majority of the permanent house plants, the ivies, philodendrons, ficuses and others, require very much the same treatment and no special differentiation need be made in their regular care.
Others with less green fingers will proclaim with a kind of wry pride that they can kill any indoor plant almost in a matter of minutes!
If I may be personal for a moment, my own resident house plant population in my country home with its clean air, large double glazed windows and central heating, varies from about 5o to loo plants, depending upon season, for some plants go outdoors or in frames during the milder months. Some of these plants are in south windows, some in north.
There can be perfectly genuine physical reasons why certain house plants fail to flourish with a certain person. The house can be too hot or too cold, too dry or too damp; the air may be polluted with domestic gas or industrial fumes; the light may be too poor either because of small or dark windows or because of grey city smog; even the domestic water supply may be too hard or too heavily chlorinated for certain plants.