Outside of local edible vegetation, there is smaller game. And as you say, this is how many used to survive.

But beyond that, you can plant beans and have a crop in weeks. Even with a lack of pesticides and fertilizer, being able to plant a plant here, a plant there, will result in food not being eaten completely by pests.

And the ground is far more fertile, when not monocropping.

And yes, seeds can be reused, it's how farming still works today for many farmers.

To speak to this, where I grew up, many people would go into the woods, and plant a single pot seed here, another there, always close to trees etc, so overflies by police helicopters wouldn't see a crop.

Being rural, some people owned 1000 acres, and plausible denialability exists. Even if some went missing, the scatter method yields results.