Can I place Pot in a hole dug in the ground?

Well you sound very organised Sam. You certainly could plant things in sunken pots, but the roots would be restricted and would also try to get into the ground underneath, making it more difficult to dig them up if necessary.
I wouldn't worry about insulation as the surrounding ground would insulate as well as any other plant in the ground, I would say.
I'm not so sure about placing feet or bricks underneath though as if the roots did need to expand, they would be sort of 'hanging in the air' unable to get moisture.
Yes, Clematis would need quite a depth in case of clematis wilt.
If you did punch tiny holes, I think you're right in saying the roots would tend to come out.
Good luck Sam and maybe you won't need to down-size, I hope not.

Hi Mad,

Thanks for your rsponse.

Just to clarify that I don't intend to cut open the bottom of the pot (as they do in case of Suncken pots). So it is as good as normal plot planing except that it is placed inside the hole in the ground.

Also I would make sure that I would use larger pots where a plant can live it's entire life. e.g. I got an information on taylorsclematisnursery (RHS Gold medalist) that Clematis can live entire lifetime in 18" by 18" pot.

With that in mind why would roots try to get out of the drainage hole?

If that's the case then what would happen if plant is in a pot on the ground planted in a normal way?

I have a clay soil but being on a slight slope we have never had a waterlogging before so I think the drainage at the bottom of the pot would be ok. Still I could fill some sand and fine gravel layer couple of inches below the bottom of the pot.

Regards,
Sam

I once sank a pot into the ground to grow mint, as it tends to take over, it grew well, but the roots found their way out of the drainage holes into the surrounding soil. Have you noticed how some weeds, and even plants find their way through the tiniest cracks in concrete? I think that sand/gravel, as you say is a good idea.
I have read that plants in pots for life, should have the top couple of inches of compost removed and replaced annually.

The chances of roots NOT coming out of the pot are remote, I'd say - they always make a bid for freedom whenever there's a chance - ever seen a large plant in a small pot on a patio? And when you try to move it, the roots have come out the bottom and penetrated through a crack in the paving and are using the soil beneath for sustenance. Even my houseplants, when contained in outer pots, push their roots out through the bottom of the pot they're contained in, and that's without any soil to enter outside the pot.
Unless you suspect you're going to have to move within 18 months, just make yourself a garden and strike cuttings as things grow and mature, ready to take with you if you do have to move. Perennials can be divided, by and large, so pieces can be taken, and any gardener always leaves a lovely legacy, or should do, in a garden when they move - after all, the plants and soil aren't yours really, any more than our children are - you're only the caretaker, they're living things which will lead a life of their own, long after we've gone, hopefully.

Thanks for your advice.

I have dropped the plan to sunk the pots and decided to go with Air-pots and do root pruning every 2 years.

For winter I will wrap up a fleece and for summer I will surround the pots by other small pots of trailing Ivys to shade the roots.

I agree with you bamboo about legacyand that plants are not mine; but at 37 years and starting out in gardening, I guess I am going to be a bit possesive about my hardwork in growing plants. AT present waiting for a plant to grow and flower after a year or 2 seems like a huge patience testing thing for me.

When I will become a more natural and experienced gardener I would be able to let go and grow more.

Thanks as always
Sam
Leeds