Indeed. Most people havent got the land to be sufficient and its practically impossible in the UK.
There are however plenty of easy to grow crops that dont take up excessive space.
For you for example you could plant some garlic in your wildflower beds and it would fit right in. Then harvest late summer.
Potatoes easy to grow, tub/bag fill with compost plant a few pots, profit. But they are not space effective.
Many of the expensive stuff like fresh herbs, chilis are also pretty easy to grow in pots. Things like chilli plants look nice.
Couple of tom plants in a grow bag, some runner beans up against a wall etc. Little work really.
Lots are quick and easy to grow on a small scale.