Alternative food sources.

Emergency Baby Formula - Breast Milk Replacement.
2 1/3 cup distilled water. Warm to help dissolving of ingredients.
Add
1 12oz can of PET or Carnation Evaporated Milk with Vitamin D
Add
2 tablespoons of Brer Rabbit Black Strap Molasses.
Put contents in a sterilized Quart jar and shake well to mix.
Keep unused amount in refrigerated after making. Keep no more then 2 days. May be rewarmed for use.
If feeding with this formula more then 3 days, a vitamin supplement drop is recommended TAKEN Separately. NOT PUT IN THE FORMULA!

We used this in conjunction with Vitamin drops and used the formula he could digest when we could get it. It accounted for at least 75% of my sons diet till we started introducing solids at 14 weeks.
Very important to keep everything as sterile and clean as possible. If it comes down to needing to use this formula, keep in mind that the Baby will be missing the benefits of nutrient in the breast milk and formula that help with immunity's.

By the way our son is now a very happy, healthy 16 year old. Who lifts weights and enjoys hiking.

How about Dandelions. Tops and greens. Are both delicious.
If you like a little bitter then pick them when they are older. If you want the tops sweet, and the greens spinachy, pick them younger.
I like to pick the tops in all stages because that way each one gives you a slightly different taste experiance. They have Vitamins A, C, K, Folic acid, potassium and calcium.
I fry the tops all different kinds of ways. Pancake batter, fish batter, corn muffin mix. Sometimes I just dip them in egg and fry them in bacon grease. Or to actually get a good taste of bud, I will just steam them.
The greens to me are best boiled or steamed. Just to where they start to wilt, but still have some firmness.
Then had with a little vinaigrette dressing.

I am actually picking some this morning to make dandelion vinaigrette dressing. For an raw leaf dandelion salad in a few days.
Simple dressing to make. Half apple cider vinegar half white vinegar.
Dry the dandelion out like you would flowers, or peppers, Put the whole dried dandelions in a quart jar fill the jar with them standing up but not pushed down in. Then make sure it is topped off with the vinagar mix. Sealed for 3 days. Use a plastic lid or a piece of plastic over under the lid, to keep the vinagar from eating at it.
Then strain the juice. Add a Clove or so of crushed garlic, and a little onion in any form, I use onion flakes. A table Spoon of sugar, and a table spoon of black pepper. Top off with olive oil, and enjoy on another day on whatever type of salad you like. Will keep a good while.

As for Rhubarb I grow it. Have a patch. set from my mother's old patch. Had to try 3 different places. The 3rd was the charm.
The stalks are not poison, my brother and I used to chew on them them raw all the time.

However the leaves contain oxalic acid. But in low levels. If you cook down 20 lb of leaves in water till you have a gallon of liquid, you can use the liquid as a bug spray for other plants.

However You can eat a pound of leaves in a day with out absorbing enough oxalic acid to do you any harm. However it might give you a belly ache, if you ate a pound raw. I takes like 30 grams of the stuff to stick in your body long enough to do any harm.
Most leaves I have ever been able to eat in one sitting, is just a few leaves in one day.
Wrapped around a pork and rice mixture, like a pig in a poke, or Italian grape leaf type wrap. Very good that way, rivals grape leaves
Never ate them raw, as a habbit. Tried one once raw, not very appetizing.

If some one wants to challenge me on this will make a video of me eating a stalk raw. Which would be slightly unpleasant to eat a whole stalk quickly. As they are quite sour, and stringy. Then you all can watch me.
While I do not die. But make ugly pucker faces, and struggle with my missing teeth to chew it.LOL.
The seads however are very toxic.
Best way to have Rubarb is in a strawberry rhubarb pie, or cut up in small pieces then cooked down in a pot with sugar and dumplings.
Poke I grow too.
Now poke does have a poison also. But is fairly non poisonous when tender, in the spring and early summer.
But toxic levels increase to more dangerous, as it gets to late summer, and it is absolutely dangerous in the fall. The berries will absolutely end your life without a stomach pump and some quick medical attention. My mom used to bring it to a boil, as do I, and drain it three times, then finish cooking. This leaches the poison. If there is any in it yet. Plus makes it very apatizing .

When doing my survival thing I picked a batch of leaves during the fall, and cooked it without doing the boil thing. I had the worst case of diarea, stomach cramps and dehydration over about a day, I believe I have ever had, before or since. Well not the worst. Had the bird flu that put me in the hospital and destroyed my health to this day. But you get the idea.

Oh and Guinnie beans, DO NOT BOIL THEM IN STEW WITH CABBAGE, AND TOMATOES.
Rather do and then report back here about your after dinner experiance.LOL

it's just the rhubarb leaves that contain the junk.
the stalk is clean, put a little salt on it and mow it down.

NC.
mint can be controlled and even removed if you grow it in a raised box.
i transplanted some from the front of my place to a 3'X3' box out back and raised it for about 3-4 years.
then i ended up enough dried [and jellied] mint to last me forever and just removed it in the spring.

the key is to wait till it wants to go to seed, then cut the stalks off and tip them over in the box till they dry, then strip the seeds off directly in the box, bag the stems and trash can them.
that'll bring them back year after year.

if you want to remove them, cut and trash bag while green or after stripping the leaves.
then in the spring as soon as the ground thaws just shovel the roots out and discard.

as far as the horseradish contain it and just dig up what you need.
if you try to rototill it or mess with the roots in any way you just end with more and more of the stuff.

If we're talking low-effort, high-yield food plants:
Purple Basil - you can use it for tea, salad, a flavoring for "spirits" or as a spice. It is good for your heart, high in vitamins, and the leaves can be used to clean wounds because they are antibacterial. Negative: It will take over your yard. No matter where you plant it, it will sprout somewhere else.

Many species of elephant ear - tasty, good to wrap meat in on the grill, and many varieties have tasty roots. One Polynesian varietal is poi, and an Asian varietal is taro. Taro tastes like the best sweet potato you've ever had. We have taro and Bac Ha growing in our yard. Bac Ha doesn't have much flavor, but absorbs and enhances the flavor of what it is cooked in. Eaten by itself, raw, Bac Ha will reduce flem if you have a bronchial or sinus problem.

Daikon - it's technically a radish, but the texture and flavor is more like a cooked carrot. Really good pickled in vinegar. It is one of my favorite veggies.It also helps arthritis, is an immunobooster, helps with allergies, and combats IBS.

Russian sunflower - they do better in the South than other varieties, with the bonut that they have a really high seed yield. Assuming nothing upsets ours this year, we're looking to have between 8 and 10 pounds of seeds.

Millet - good in hearty soups and can be made into bread or beer or something like grits. The beer comes out looking and tasting suspiciously like Bud Light, regardless of whether it is made as an ale or lager, but smells like a heffeweissen. It is very dissapointing if you are expecting it to taste like it smells.

Then there are the "weeds":

Clover - edible...sort of. It is safe to eat, but purple and white clover are the only ones that don't taste like fertilizer. High in nutrients, and taste good jellied.

Collards and mustard greens grow wild in every ditch around here. I'm not a fan. I think collards taste like lawn clippings.

Poke salat - edible if you know how to cook it, in theory, but only palatable with fatback, and preferably cooked by an old lady who calls everyone "hon", "baby", or "chile" - so mostly white ladies over the age of 70, and black ladies over the age of 50.

Milk thistle - the leaves are kinda like spinach, the roots of young plants are kinda like carrots, and the flowers are like artichokes, and some people (not me) like the seeds roasted. The stems can be "milked" for medicinal purposes.

Dew berries - these grow wild mostly east of here

blackberries - these grow wild a little north of here. They used to grow here, but people mostly killed them off as briars.

deerberries - they are in the blueberry family, but sweeter and smaller. The hard part is getting to them before the squirrels and deer.

pawpaws - like deerberries, about the time theyre ripe, they have all been eaten by other animals.

mock strawberries - they are really healthy, but taste like the water real strawberries were washed in.

wild strawberries - less common than the mock. Delicious, but it takes hours to get enough of them to fill a bowl

muscadines/scupadines - they magically appear on any untended fence in Alabama. You may not even know they are there until a neighbor asks if they can get some. Often better than grapes, and make good wine if you painstakingly take the seeds out before fermentation. I've been saving a bottle of blackberry and muscadine wine for a special occasion.