What do you think about neighbours helping themselves? Wandering on this private property, picking the unblemished fruit and distributing it to family and friends? On the one hand, it makes perfect sense; on the other it is, no doubt, illegal.

The exchange of seeds, cuttings and plants (not to mention the less-mutual plucking from other people's land) has been going on for as long as people have gardened.

But ideas around ownership and usage are now being analysed afresh.

Last month, the owners of a derelict slice of vacant land in Collins Street agreed (as part of Lord Mayor Robert Doyle's re-election bid) to let the Melbourne City Council and a city restaurant plant the block with vegetables for the foreseeable future.

In a similar vein, six years ago North Fitzroy resident Glenda Lindsay turned over a large portion of her backyard to those living nearby to grow food. Ever since, between three and seven other households have used her garden, entering whenever they like through a locked gate. It is an all-in-one arrangement with no individual plots, and there are rosters and working bees for the delegation of jobs. Part of the appeal for Lindsay is the idea of reintroducing food-growing skills and ''sustainable food systems''.

Such an arrangement has been taken a step further by the Landshare Australia website (landshareaustralia.com.au), which provides a means of connecting those with land or labour to share.

Just as Landshare, which began in Britain three years ago, encourages people to cultivate food on underutilised garden spaces everywhere from Queensland to Western Australia, other websites encourage people to make use of productive trees. Feral Fruit Trees Melbourne (feralfruitmelbourne .wordpress.com) maps the precise whereabouts and details (''Late autumn fruiter, black figs. Overhanging back lane, lots of fruit''; ''Plum … small red variety overhanging fence, some are quite high up'') of privately grown trees. The idea being that if members of the public don't pick the fruit, it falls to the ground and rots.

The website outlines a code of etiquette: take only as much as you need, don't damage the tree, show courtesy to the owner.

Even the latest Little Veggie Patch Co book (Guide to Backyard Farming) includes a how-to chapter on foraging in the neighbourhood with a photo of founders Fabian Capomolla and Mat Pember reaching for overhanging lemons. But Juliette Anich, who set up the Sharing Abundance site (sharingabundance.org) as part of a PhD exploring alternative food systems, says some of the thinking behind such sharing (or taking) of produce is highly controversial.

''It is an interesting thought-provoker on the idea of what is yours and what is mine, and how are we going to divide it,'' she says.

''Foraging and scavenging can have bad connotations, but I am thinking it can be nicer, friendlier and more welcoming.'' To this end, she has devised a system whereby volunteers harvest ''seasonal abundance'' that is then split three ways: between the owners of the tree, the volunteers who did the picking, and a local community enterprise such as a school.

On her food maps (which are currently offline) she is building in a facility that allows owners of trees that have been plotted to remove their specimen should they wish.

Anich is also developing a signage system, whereby notices will be posted alongside plotted trees telling people to take only as much as they need, or to leave the fruit alone because it is to be harvested at a certain point in the future, for example.

Anich sees the Sharing Abundance website as a way of bringing back something of the everyday seed-swapping and information exchange of previous generations.

While neighbours will forever pass around their surpluses of tomato seedlings and join together in garden clubs and the like, the internet is helping forge less local connections.

So are the plant and food swaps being organised around town. Fitzroy Urban Harvest, for example, takes over Smith Reserve on Alexandra Parade on the first Saturday of each month (including today) for the exchange of produce, plants, gardening tips, recipes and the like between people who don't necessarily live nearby.

While there is some potential for these activities to expand into purely ornamental forms of gardening, they are currently centred around food plants and stem from ideologies about climate change, food sustainability and fostering a sense of community.

Anich says it has been put to her that the take-up so far of food mapping and other such exchange initiatives has focused on ''middle-class do-gooderism''. ''But it has to start somewhere,'' she says. ''And that's a good place to start.''