what is the best and safest weed killer one can used now in your garden?

None.
The way chemicals have a habit of biting one in the butt years down the road, I avoid them at all cost! I how, till, cultivate and mulch to keep the weeds under control. I'll get down on my hands and knees if I must, but I refrain from chemicals.
Most current example:Roundup. When it first came out, it was the safest and best stuff around and now look.

A organic alternative to Round up is--4 cups of white vinegar, 1/4 cup of salt, 2 teaspoons of Dish soap per gallon of water. Its best to use when its hot and dry and you still may have to spray more that once. Don't use on lawns because it will spot the lawn. Works super between stones on a walkway or patio areas.

I knew some body would have a recipe!! Thanks Luke!!

Thanks Bill.

Welcome

Go on Amazon. Horticultural grade vinegar, 20% and plus by the gallon or more. No recipes needed. Straight forward. Works very well. There are plants that will kill tough weeds like quake grass and most broad leaf weeds. You can lay the leaves on the offenders and they will be dead in a few days. No seeding weeds will emerge either.

Oddball thing here- I once (way back in my youth) wondered if I could help my plants by spraying them with cooking spray- Pam for example for baking, - you know, horticultural oil exists so why not lol- and found the leaves fried nicely in hot sun. So I could imagine experimenting with spraying individual plants on hot summer mornings with cooking spray and letting the leafy part get fried up. Again, repeat for total kill. But seems very non toxic and biodegradeable.
Open to comments on this...

Well I'll comment because I am a big Neem Oil advocate. Living in the heat of Florida made application times very difficult. And as sallyg mentions, these oils can fry the plants once the sunlight hits them. Cooking oils too.
I would apply Neem Oil very early in the morning, by 8am. Since daylength is very long in the summer, I used a series of oscillating fans to dry the Neem Oil spray. The fans would have those plants dry by 10, 10:30am. The intense sun would start to impact my growing area at about that time.
My other option was to spray late in the day as the sun left my growing area which would have been around 5:30 or 6pm. Using the fans, the plants were dry by nightfall.
Neem Oil application is difficult during the dry season because the sun is still strong but with drier days with less humidity, the plants were dry in a half hour to 45 minutes.
To keep things from burning required a bit of diligence on my part.
The additional problem can occur because people apply Neem Oil without diluting it. They apply it for consecutive days. When they describe the reasons behind those applications it seems to me that they have panicked to some degree. I doubt that very much in the way of good results ever come from a panic.
I guess what I am trying to say is that we all garden, we all have bugs, and we all have to learn from experience how to deal with these things. It is all about remaining calm.

with BigBill

frogfan said:Go on Amazon. Horticultural grade vinegar, 20% and plus by the gallon or more. No recipes needed. Straight forward. Works very well. There are plants that will kill tough weeds like quake grass and most broad leaf weeds. You can lay the leaves on the offenders and they will be dead in a few days. No seeding weeds will emerge either.

Froggy has it correct, it kills and then goes away with rain.
If it is a deep root weed, digging may be your only cure.

sallyg said:Oddball thing here- I once (way back in my youth) wondered if I could help my plants by spraying them with cooking spray- Pam for example for baking, - you know, horticultural oil exists so why not lol- and found the leaves fried nicely in hot sun. So I could imagine experimenting with spraying individual plants on hot summer mornings with cooking spray and letting the leafy part get fried up. Again, repeat for total kill. But seems very non toxic and biodegradeable.
Open to comments on this...

Me thinks PAM is more than oil.

The main ingredient in Pam cooking spray is canola oil, known to be low in saturated fat, high in polyunsaturated fat and monounsaturated fatty acids. Canola oil is produced from the rapeseed plant which has been genetically modified to be resistant to pests, herbicides, and weather. The safety of genetically modified foods has come under fire due to adverse side effects, and most health-conscious consumers prefer to avoid (Genetically Modified Organisms) GMOs when choosing food for their family. GMOs are notorious for causing a multitude of cancers and other life-threatening diseases, in order to for the producer to make products larger, faster, and more appealing.

Soy lecithin is another ingredient in Pam cooking spray. Soy is another genetically modified plant; 91% of all soy products in the US are GMOs, according to the USDA. Lecithin is an emulsifier and helps hold the ingredients together. Derived from the soybean plant, soy lecithin is the part that's left over following extraction of soybean oil. The Soy Info Center describes it as a brownish sludge which is then processed with hydrogen peroxide and finally extracted using acetone.

Pam cooking spray is produced by the food manufacturing giant, ConAgra, which has come under fire recently for using genetically modified foods in its "all natural" brands.

Of additional concern are the propellants used in spray cans. Cooking sprays typically contain hydrocarbons, highly flammable substances, which should not be used near an open flame. According to ConAgra, the specific hydrocarbons used in Pam cooking spray are food-grade, FDA approved, butane and propane.

The answer is-- it depends. It depends on the weed and what's around it.

For broadleaf weeds in turf, something like Trimec works well.
For grassy weeds in groundcovers or flowerbeds, Poast and Fusilade work.
For nutsedge anywhere, Manage or Sedgehammer work.
For tough weeds like bermudagrass or bindweed, your best bet is Round-up, if there is nothing else growing nearby. You can make a protective collar of cardboard or plastic to protect desirables nearby.

ALL of these are safe in the garden as long as you follow the directions, follow the directions, follow the directions.
Also, when in doubt take a large sample to your local independent nursery- like Armstrong

Vinegars are a good choice, but they are non-selective. This means they will at least damage everything they come in contact with, weeds or good plants. Just because something seems natural and relatively harmless doesn't always mean something is good, but as previously mentioned, vinegar dissipates easily with rain or water. This is one of the hallmarks of more environmentally friendly pesticides. The down side is that it doesn't do much for killing strong root systems.

Please don't ever EVER use salt in an area you wish to grow plants in at a later date. Salt remains in the soil for a long time, rendering it a virtual dead zone for plants and all the good healthy soil flora.

Vinegar should be applied in full sun always after 10 am. The dew will burn off by then and prevent dilution. Spraying will suffice for smaller plants. Successive applications for larger plants and root drenching. Look at the weather before applying. The damage from the vinegar open plants up to invasion by pathogens as well. If you have used it you know.

If I have problems with weeds, vinegar is the best for me but don't overdo with its concentration.

I was looking for a good weed killer for a lot of years. I have pretty big own territory and to clean it up using trimmers, I should spend more than a week. Only propane torches help to ease the situation. It is an irreplaceable thing in the garden, really don't understand how it is difficult to keep order without it, especially if you have trees in the yard. On https://homendgarden.com/best-weed-killer-torch/ there is a nice list of the best weed killer torches for pretty low prices. And, of course, it is totally legal to use it in the states (I live in Orlando)

Miscanthus grass can be laid down instead of wood cuttings. The grass will inhibit weed seed emergence for the growing season. It does not break down like wood. So it does not steal nitrogen from your plants like wood does. You can bale it and keep it in the open uncovered without worry of composting. That is why it is now used in some areas as a fuel and is being pelletized for stoves and animal bedding. It is the best for animals because it does not mold like straw or wood. I have cut it green or dormant and it will kill actively growing weeds. Makes a natural ground cloth. You can plant a garden in it. No weeding for the growing season.

http://hoffmannursery.com/plan...[]=Miscanthus