If it is necessary to control ants, and in the garden it really is not, a mixture of 1/4 cup water, 8 teaspoons of sugar, and 1 teaspoons of Boric Acid is what you want to use. Hot water will make disolving the sugar and Boric Acid easier but let it cool before placing it where the ants can find it.

"If it is necessary to control ants, and in the garden it really is not..." When I lived in OH I would have agreed with this, but I disagree now. Fire ants are not welcome to take up residence in our yard, and other ants can be so numerous that it affects my ability to be able to garden when and where I want. Often I can't finish something I started because the area is swarming with ants who will get all over me and bite if I don't leave. They swarm into potted plants, and into the car. I don't know if they leave because those little bait things really work, or just relocate because they are disturbed, but when I encounter a swarm where I can't tolerate them, I "feed" them one of those.

Try pouring boiling water on the mounds. For potted plant infestations, you'll have to wash them out of the root ball and repot, or you can use Amdro.
Thankfully, once they get in your car, they don't survive long.

Good point about the boiling water.

I can evict them from pots by submerging the pots in plain water. Just pointing out that there are instances when even people who don't own any chemicals find it necessary to take a proactive stance with nature.

It's sweet how y'all up north talk about the ants. So innocent...

Buying the ant bait things is the first time I've bought any kind of chemicals in about 15 years.

Lol, purple! I'll never forget the time that a gazillion fire ants decided that my car would be a good place to visit. Naturally, they didn't make their presence known until I was traveling down the road at 60 mph!

These ant hills are in my horse pasture. The one must be at least 3 feet across. I need grass growing there, not huge ant hills. Also, we were sawing wood near one of the hills, and they started crawling all over our shoes and socks. I want them gone.

But the borax also kills all the vegetation for a long time, i.e. years. So wondering what the correct percentage of sugar to borax would be, so it does the job on the ants, but won't kill the vegetation for years to come.

You need to forget the home remedies and find a commercial ant bait. Call your local county extension office and ask for the appropriate product for your horse pasture. There isn't a "correct " amount of borax for use on vegetation. Period.

The extension service is designed to come up with solutions for just this type of situation.

steelskies, I have obtained very good results using 'Hydramethylnon' - the a.i. in Amdroâ¢.
Take the pains of not applying the product on the mounds.
If the bait starts to spoil the ants will throw it out and avoid it.
Ants like to forage and bring food into the mound. Facilitate this by applying the bait a little bit away from the mound.
Do not over apply. The label has some cautions about this.