If your soil is heavy clay, it will not help to dig a hole and fill the bottom with gravel. The surrounding clay may act like a container that holds water. Your alpines would drown as quickly as if they were planted directly in wet clay. I do think that filling in around pots with gravel would give the plants the drainage they need. If your property has any slope try using that as a base for the rockery. Set larger rocks and small boulders at the bottom of the slope. (A boulder is any rock larger than 10x10x10".) Position potted alpines along the slope with a few larger rocks and boulders to hold everything in place. Fill in with gravel to the top of the pots. Make sure the soil level in the pot is also at the rim. As the plant grows the edge of the pot will be hidden. You could also paint the top of pots to match the gravel color if needed. Here is PHOTO 1, PHOTO 2, PHOTO 3.

I see no reason for you to remove the pots during winter dormancy. Alpine plants are found at high altitudes above the tree line. Most of them go dormant during winter. You should seek out some dwarf conifers to keep some winter green. HERE is a list of some alpine plants grown in a Canadian garden. This garden is not a raised bed. It looks like the plants are set in regular soil between some rocks.

Thanks for your reply. Sorry it took a little while to respond. I see what your saying about the clay going to retain the water around the pots. So when you say filling gravel around the pots, do you mean backfill the hole with gravel after the pot has been sunken down in the hole? Will the clay eventually start leaching into the gravel with the rain? I also thought about putting a pot in a much bigger sized pot that is already sunken in the ground and fill that bigger pot with gravel. That way you know the soil around it won't be around the pot with the plant in it. And maybe you can cut out the bottom of the bigger pot so water can drain better. And of course there will still be gravel under it. Does that sound better? I also do not have any slopes in my garden, it is all flat surface...

I want to remove the pots so the plants won't suffer from winter rain which can cause the plant roots to rot, especially when alpine plants require excellent drainage and dry winters AND that they are in a pot which is less breathable inside.

Those pics gave me an idea.. I guess I can pile up a couple of rocks and create soil between them. I still like to stick to the idea of sinking pots though so that will ensure voles don't get them especially since they are prevalent in the northeast and you never know when they will invade your area. Although, if the soil was rocky enough maybe the voles would avoid digging through it?

Also I already have a list of my alpine plants if you want to know. They are: Achillea sibirica subsp. camtschaticum, dracocephalum argunense, chrysanthemum pacificum, sedum rupifragum, hylotelephium erythrostictum, aquilegia flabellata var. pumila, allium schoenoprasum, and thymus quincecostatus.

A pot inside a pot full of gravel inside a hole dug into clay is still in a hole that could fill up with water. Put the pots with plants in them on top of the clay soil and fill in around them with gravel. It's a bit like making a tiered garden—some pots are set an inch or two above the base soil; the next group is set atop deeper gravel; a few are set on a still deeper gravel layer. The edge of this area is made of small boulders and cobble. More boulders/cobbles are used to create an abrupt level change, but most of the gravel will be a mix of sizes between 1 and 3 inches. You don't want even sided levels. You want gravel slopes that meander down the sides of this area. You can use rounded gravel, though crushed gravel looks more like scree. It's more important to have the color of your gravel, cobble and boulders be similar. Since most alpine plants are growing in thin soil over a layer of scree, you can even use a mix of pea gravel and potting medium. Check the cultural requirements for each plant.

Because the pots are surrounded and sitting on gravel drainage will be excellent. But you are worried about too much rain, and it sounds like you are using plastic pots. You can increase drainage and air infiltration by drilling 1/4" holes in the sides of the pots. Make holes about an inch apart on all sides from top to bottom. I know, lots more work, just what you wanted. It may not be necessary, and is just a solution I picked up from an orchid grower.

The fact that your plants will be in pots and surrounded by gravel may keep the voles at bay. Animal activity is not always predictable. Deer are my biggest problem. They sometimes eat deer-resistant plants, and if there is a drought even the reliably resistant plants will be munched on. Sigh.

Your list of plants is really nice. I looked up most of them, though I could not find them all. Best of luck. Gardening is all about optimism. - Mary Anne Radmacher

But when you put the potted plants right on top of clay soil wouldn't that cause puddling underneath when the pot gets watered? Or do you mean gravel below it? Like maybe a foot or foot and half of soil should be dug out and fill with gravel and then set the plants directly on top of the gravel and then you surround it with more gravel you mean?

And for the potting mix, you recommend a mixture of commercial potting mix and pea gravel?

Deer is also my biggest problem here as well. So far there have never been voles but that may change and I rather protect it sooner before its too late.

I have from the beginning been saying don't dig a hole. How is it you worry that setting pots on top of the clay will cause a problem, but digging a hole and setting the pots in the hole won't cause a problem? Here is a cross section diagram of what I think you should do. As I said above:

" Put the pots with plants in them on top of the clay soil and fill in around them with gravel. It's a bit like making a tiered garden—some pots are set an inch or two above the base soil; the next group is set atop deeper gravel; a few are set on a still deeper gravel layer. The edge of this area is made of small boulders and cobble. More boulders/cobbles are used to create an abrupt level change, but most of the gravel will be a mix of sizes between 1 and 3 inches. You don't want even sided levels. You want gravel slopes that meander down the sides of this area."

Yes and I keep asking because I want clarification on my question that you still haven't answered. When the pot gets watered and once the water comes out of the bottom of the pot, it will hit the clay soil underneath forming a puddle rather than draining right through it because it's clay. And even if it does drain it will be super soggy below that plant roots won't be able to breathe from the bottom holes. Is this logic correct and does that actually happen or no?