I have no help or suggestions I'm just surprised you were allowed to adopt and then let them be outside...On our adoption contracts, it's stated, cats/kittens must be inside only.....Good luck with your potty problem......

Actually your flower bed provides them the perfect place to poop, nice soft tilled soil...there are several ways of dealing with this problem, none of them involve a garden hose.
You can place a cat box, complete with kitty litter near the area they are using, and slowly over weeks move it away from the garden, You can get them with a cover, so the flies are not so bad, you will need to pick up the poop. which you can do now if you dont like the flies, and put it in the trash. You can get some spray - sold at most pet stores which you can spray in the area. It will need to be reapplied often. You can try picking up the poop and placing it where you do want them to do their business, this might help them get the idea of where to go. You can put in some short term deterrents like foil, an old cookie sheet or whatever fits in the space in your garden...please be sure to spay and neuter those kittens so you dont have an over population of cats, unless they are already fixed, in which case, good luck with your new furbabies

I have indoor/outdoor cats and I make it a point to keep them inside only until they have been "speutered" or at least until they are big enough not to be hawk-bait.
Once they go outside, they will stick around very close to home-base and eventually go exploring more and more, at first they will come inside to use the litter-box. I also leave the door ajar, because home is their safe place.
Now my youngest are a little over a year old and I have no idea exactly where they poop.
When the weather changes, they will spend more time in the house and use their indoor plumbing.
I suppose you have some shelter for them if you want to keep them outdoor cats exclusively?
As your kittens are just babies, I would offer them a litter-box close to home and move it away little by little.
It's inconvenient for a little while, but they grow up so fast.
Personally I like my cats to be inside as much as they want to be, even though daytime it's perfectly safe for them to be outside, and at night they do come in for a treat and then all pile on my bed and keep me warm, whether I need it or not

We have an entire family of barn cats... I never see the adults relieve themselves, but the youngsters use my planters, the garden areas, my potting soil tub... anywhere convenient.

I do believe they'll grow out of it as they mature, and go off to find more private places to use... they'll also bury it, as that's the general instinct of cats, to cover their leavings/scent.

It's just a matter of time...

The problem may be your mulch. A lot of mulches have tiny splinters that can actually stick in the pads of dogs and cats. And some of it even clings to their fur.

When I had mulch put in my yard a couple of years ago, I couldn't touch it without wearing gloves or I ended up with the splinters and itchy hands. It has now broken down and isn't a problem, but I'll never put that type my yard again.
Before trying to train them to use that specific area in your garden, you may want to change the shredded mulch to a soil based mulch.

Hi, I have seen these in several gardening catalogs and wonder if placing a few of them in the kitties' favorite places near the patio will discourage them.

Here is a link that might be useful: cat scat

I would think it would be a heck of a lot easier to keep them inside until they are trained to use a litter box or at least an enclosed area outside. I can't imagine a kitty or cat wanting to not bury. This is one way of marking their territry and if they keep this up you may never get the smell gone enough for themm to not want to use the patio areas in the future. Years ago I let my DIL stay with her cat in the house and she got into the habit of peeing near a closet. DH's cat soon started using the same area. I went crazy trying to deodorize the area until I just had to replace the flooring. Good luck.

OK - Things are a bit better now. The white cat has learned to bury. I emptied the litter box near the big mulch pile and that made the tiger kitty figure out that was a good place to do his business. I couldn't believe how successful that was. One more cat to go, but I believe, as jodik says, that as they get older they get more discreet.

Nancy in mich, those mats would be ridiculously expensive for the area I need to cover, but you gave me a great idea. I cut some barberry brances and laid them over the areas that I want them to avoid. That also works.

Thanks guys! Your ideas are working.