Almost half the world is going hungry, and an even greater proportion can't afford nutritious food.

"From the ground" is a good answer or even "from the farmers market", because that implies the kid knows that a farmer grew the food.

A fabulous answer would be a long lecture along the lines of "the eggs came from Aunt Beck's chooks and the pumpkins are from Mrs Patwa down the road and I picked the lettuce before dinner and Uncle Lee made the green tomato pickle..."

Possibly the most basic knowledge our children need - the children who will grow up to be politicians, teachers and voters - is that food comes from soil and sunlight, or sometimes nutrients in water and artificial sunlight, but that food is always grown. If war, pandemic, drought, bushfires, sandstorms or civil unrest means that crops fail, or can't be transported to where they need to go, then people will be hungry. It can be expressed simply and simplistically with: "If you don't look after the planet, you may not get your dinner."

Apologies for the lecture, when you were excepting gardening. But gardening can be - often is - the most essential way of teaching kids and adults how to care for country, starting with a backyard or nature refuge, and how food can be grown, even if it's just a potted orchard of dwarf fruit trees on the balcony.

Backyard, school and community gardens are also places to show that we don't have a global fertiliser shortage: we have a nutrient recycling shortage. Plant tucker can come from whatever once grew, from trees to fibre doormats, newspapers, sewage, hen and other manures, and composted weeds. A good place to start is to show kids how to make homegrown compost and mulch.

Even more importantly, backyard, school or community gardens are a place to teach kids that food can be shared with others, because as planetary disasters increase, there will be more times when we need to give, or ask for help.

Just now I'm trying to give away chokos, rhubarb, arrowroot, lemons, tamarillos, medlars, Tahitian limes, native finger limes, as well as vast bunches of gold or purple salvia. Flowers nourish us in other ways. Soon there'll be cuttings of those salvias to give away, as well as tree dahlias.

Okay, you may not have green thumbs, or even a free 10 minutes to spend gardening most weeks. But plant a lemon tree, or a dwarf mulberry, or perhaps a pomegranate or two, a persimmon, or an Earliblaze apple or maybe an apricot - all fruits that need little tending or pruning, though they will be happiest if you give them slow release fertiliser and mulch every spring, and water now and then in dry times. Plant a loganberry or thornless blackberry to ramble along the fence or maybe a couple of kiwi fruit.

In turn they will give you lots. So much that you will need to give some away. And when kids arrive with mulberry-stained hands, or an armful of lemons and a demand that it is time to make more lemonade, there will be no need to ask them if they know where food comes from. They will have the security and the resilience of kids who know how easy it is to turn one potato into a bucketful, how boxfuls of almonds can come from a single seed, how suburbs that grow roses and grevilleas and kangaroo paws can also grow enough food to feed every person there - and enough to give away.