Chock full of errors…
(Yes, chock, not chalk. Seriously…)
Etc. is an abbreviation (stands for et cetera, which is why we, y’know, pronounce it that way); treat it as such by putting a period after it. If having it at the end of sentence causes problems because you’re not sure if the period for the abbreviation means you don’t need a period to end the sentence, just spell it out as et cetera. (Also, anything inside parentheses gets its own punctuation anyway, so why is this even an issue here?)The hyphen (that wants to be a dash) doesn’t belong at all. You don’t have to use a comma in its place (you could just delete it), but if you do, you’ve got to have a comma before in a rare gesture of humanity, too.
The city has designed and built a “food forest” filled with hundreds of edible plants: fruit trees, herbs, vegetables, et cetera. They decide, in a rare gesture of humanity, to make it free for everyone.
Things were going well — homeless people were getting fed, children were enjoying picking the fruits on their way to school — but someone has poisoned the food, and now people are dying. Who is it? A disgruntled grocer? Teenagers? A madman? Or was it an official, and this was the government’s plan all along?
You could also do the second paragraph like this:
Things were going well. Homeless people were getting fed, and children were enjoying picking the fruits on their way to school. But someone has poisoned the food […]
Even incomplete sentences/fragments need to be punctuated and capitalized like sentences.
Now, a few comments about the science: Merely hundreds of plants won’t actually feed many people, especially if some of them are depending entirely on those plants for sustenance. You can strip an apple tree bare of fruit, and it will still produce apples again the next year, but if you dig up a carrot and eat it, that’s the end for that plant — you’ve just consumed its taproot. Herbs in particular aren’t noted for having much in the way of calories. (Neither do carrots, for that matter. You’d overdose on vitamin A long before you got enough calories from eating carrots alone. Ditto for the green leafies — some of them may even be negative-calorie foods that require more energy to digest than you get from eating them.) I’m not saying a community fruit-and-veggie garden is a bad idea. I happen to think it’s a great one. But don’t think it’s feasible to feed an entire city’s homeless population and give the kiddies the opportunity to pick their own afternoon snacks with just this.