How can I make a garden smell nice without planting flowers?
You could plant a chamomile lawn, which would not need mowing and would smell wonderful when you walk on it. Or you could plant things with aromatic leaves if you don’t want flowers, in pots if you haven’t got borders – try lemon balm, mint, or curry plant – or plant perennial geraniums and get ‘free’ flowers as well as all-year-round foliage which smells lovely when touched. I wonder why you don’t want flowers – there are so many easy shrubs which have really strong perfume and are no trouble to grow, eg philadelphus, lilac, choisya (mock orange) and honeysuckle. PS edit ; i’m just wondering if it’s the drains, or whether, if you live in the country, a farmer has been spraying liquid manure nearby.