If you are old enough to frame this question, I am amazed you do not know the answer. Here are but a few ways plants are useful to humans,

1. They liberate oxygen which you need to breathe.
2. They provide food (fruits & veggies) that you like to eat.
3. They provide feed for grazing animals that you like to eat.
4. They provide nectar for bees to make honey.
5. Their scented parts are used to make perfumes.
6. Some of them are used to make dyes.
7. Some of them fix nitrogen in the soil to enrich it.
8. They provide grazing for wild animals.
9. They provide nuts and seeds for animals and humans.
10. Penicillin and other useful medications can be extracted from them.
11. They provide nesting sites and shelter for wild animals.
12. They provide fibers for fabrics - cotton and linen.
13. They provide alcohol, Mary Jane and other recreational drugs.
14. They are part of the base of the oceanic food chain.
15. And, just so you know they’re there, their pollen gives you allergies.

A) come fonti di cibo e B) come produttori di ossigeno. Ovviamente, ci sono più di due modi, ma i due di cui sopra sono i più critici. Abbiamo bisogno di cibo e ossigeno, senza le piante l'intero pianeta crollerebbe. Quindi conta le tue benedizioni e pianta qualcosa nel tuo giardino.