Massive in-ground bees nest

Are you sure they are bees?  If you post a picture here, you may be able to get confirmation.  If they are bees, please do not kill any of them.   There are bee keepers in the area who will be able collect the swarm and move it to a safe location.  A search engine search should be able to give you names and contact information for people who can help.

Harriet said:

There are a huge number of bees swarming around the plants in one part of our yard. All the evidence points to a huge nest under the ground.

We don't want to kill all the bees, but we also want to keep the area safe for children and pets.

We've thought about using some animal/human safe products to kill some of the bees, but that is just a temporary solution.

Any suggestions?

makes no sense to kill some of the bees. Throw garlic powder on the area where they’re burrowing. Or mix some white vinegar and water and spray the area. I had some yellow jackets burrowing under my front porch a couple of years ago, I got stung as I was cleaning out the area. Right on my ankle, the pain was so intense I couldn’t stand up for a few hours. I obviously stepped on the female because out of nowhere there were yellow jackets swarming my front porch. 
Are you sure that it’s bees and not hornets? 

This company is a great resource for advice about bees:  https://southmountainbees.com/

Wasps?  Bees don't burrow underground as far as I know.

A number of bee species burrow:  https://extension.unh.edu/blog/2019/05/should-i-be-concerned-about-ground-nesting-bees-my-yard

This article recommends changing the composition of the ground to discourage ground-nesting bees, rather than using pesticide.  We need to do everything we can to preserve the lives of bees.  

I just planted some native pollinator-friendly plants out back. Some phlox, two types of bee balm and something called mountain mint. All acquired at the Maplewood Garden Club plant sale. I’m hoping that they take and spread. 

wait till dusk when the bees go back into the nest, put a jar or container over the hole in the ground with a rock on top.  Leave for 2 weeks

Those ground bees are aggressive, territorial and down right nasty

If it’s yellow jackets kill them with extreme prejudice. We had yellow jackets make burrows in our yard twice. Nasty little jerks. 

To get rid of them without pesticide this is what I did. At night when they are inactive cover the hole with a piece of window screen. They weigh it down with rocks or bricks or someone you don’t like. Pour a couple of tablespoons of dish soap through the screen the let your garden hose run into the hole through the screen for a couple of hours. They can’t get out, the soap bubbles weigh them down and they drown. 

An energetic crew of ground bees showed up in my pollinator garden a couple of weeks ago. They'll leave in a few weeks, like dry soil and are non aggressive. I'm working around them walking through the swarm and they are peaceful. Lots of online info about them

with a nod to @paulsurovell "Bee About Peace"

When I told my spouse that I had asked on MOL, they predicted that within 4 posts someone would question my original post. 

Yes they are ground bees. We did some research and decided to wait a few days. The activity stopped so we did not need to take any action. We were also watering the area more which may have helped. Morganna's post is very accurate.

Elle_Cee said:

This company is a great resource for advice about bees:  https://southmountainbees.com/

Thank you for the very useful information. I've bookmarked the site in case I hear about a local swarm.