This is such a good point. I've often wondered about this too. People who watch gardening programmes tend to be older, and, I would bet, reasonably well-educated. Even if they're not older, they're certainly interested in expanding their knowledge of the botanical and natural world and, probably, the world in general. In my view, this makes them potentially an extremely intelligent audience.
So why treat us as if we're stupid? Is it because the programme makers themselves are thick, and incapable of coming up with any decent ideas? If that's the case, I'd like to make some suggestions. These are the gardening programmes I would like to see on television:
The Plant Hunters
This could be a great series of wonderful adventure stories, combined with stunning locations, about the men who brought back so many of the plants we all grow today. The stories of people like Reginald Farrer and David Douglas could be intertwined with information on the plants they found, and the sort of habitats they explored, so we'd all know how to grow the plants properly. (Viewers might be advised to grab a box of Kleenex first though.) Roy Lancaster would be the obvious choice to present it, but he'd probably be deemed too old (ie, over 12).
The new plant hunters
The people who are doing exactly the same job, but in today's world.
Grumpy old gardeners
Like most people over 40, I get absolutely sick of the cult of youth. I want to hear people like me having a heated discussion about the things I'm interested in: organic/green gardening; instant impact; the British native plant debate; whether gardening programmes have dumbed down; are men better at gardening than women; are lawns ungreen. There's six programmes for a start. I think the participants should be female too: I'd suggest (mischievously) Helen Yemm, Anne Wareham, Janet Street-Porter (who is a keen gardener); Germaine Greer (ditto) for starters. Anyone who has strong opinions and doesn't give a stuff about offending people, especially the RHS. If the BBC doesn't think this would be photogenic enough for mainstream terrestrial TV, why not put it on the radio?
Plant profiles
Geoffrey Smith did a wonderful series about 20 years ago where each programme dealt with a different flower (rose, tulip, primrose etc). He looked at the history, mythology and symbolism behind the flower, as well as how to grow it. It was fascinating, and not exactly expensive programme-making. Why doesn't someone do it again?
Climate change gardening
This could look at how gardening trends have been and will be influenced by the changing climate, not only in terms of one's own backyard but also by factors such as the rising cost of energy and the impact horticulture makes on the environment. At the very least, it could be a Gardener's World one-hour special. No, on second thoughts, not a one-hour special. Do it properly!
Anything on trees, although the BBC, strangely, seems to be able to make quite good programmes about trees. Perhaps that's because trees come under the heading of science, nature and environment, rather than leisure, so they escape that terrible tendency to turn the programme into 'entertainment'. And the Meetings with Remarkable Trees series was based on a book, so they didn't have to think it up themselves (though they did a good job). Sadly, I missed The Trees That Made Britain series, and was annoyed to see that it's unavailable on the BBC's much trumpeted iPlayer and it's not available on DVD. Was it any good?
Right, that's enough ranting from me. What would other people like to see?