I think you might be better served buying tons of sand than more tubing and watering gadgets. The roots cannot breathe in clay and the plant dies of lack of oxygen. No oxygen when wet and brick=like when dry = strangled roots.

The best money I ever spent (and its not all that expensive) was a full dump truck load of sand, like the real high piles you see when building a new home for the concrete mixer You can hire haulers inexpensively to bring it out to you by looking in the newspaper classifieds or have the company dump it on your property. I am in the city, and don't know what your situation is, but this worked for us. Concrete grade is the best.

After adding sand I was amazed beyond my wildest expectations on how much easier gardening became and what I can grow with ease now. After years of watering, adding peat moss, organic etc, the sand was what made the biggest difference. Its so easy to water deeply and the plants take off with rapid root growth.

At a 1 to 100 scale I am now at 1.

I should have mentioned, I grew two of these Robusta Junipers in front of my house a few years ago. I got the plants at Builder's Square way back when we had those stores. They were in full sun, fairly good garden soil that drained well and grew about 5 ft per year. I had to take them out because they got way too big. We have a two story home, and by the 4th year or so, they had hit the top story windows and still going up. Thats when we dug them out. They were fairly resistant to bag worms the year we got them so bad and absolutely gorgeous trees. It was sad to take them down. I have never seen a tree grow so fast. If you made a hole about 4 to 5 ft wide with amended soil I think you could successfully grow one.

I would easily rate it on a scale of 1 to 10 for fast growth, beauty and form a 10. They weren't that difficult to take out, considering the size, so I think if you did that soil amendment in that size of hole, it seems like it would work. Be sure to give it a lot of space for width. About 6 to 8 ft minimum.

This is out in the country. The only realistic way to get drainage here, is to backhoe a 6ft wide trough all around the perimeter and fill that with a sand mix and plant in that. The slope of the property would then provide a natural drainage path. But I am not too keen on having to do that to get trees growing.

The hole size does not seem to matter with many of these. I did have amended soil with sand in them. Whether you dig a 1 foot or 6 foot hole in clay, all you have is good soil dumped into a "bucket with clay walls." So the roots will seemingly become root bound within that area unless they are aggressive enough to move into the clay.

Obviously there are wild trees growing fine all over Oklahoma. So it seems to be more related to how aggressive and adaptable the root structure is on the trees.

I may just try a few Robusta junipers to see how they do and add more if they actually survive.

I have a book called "The Right Plant, The Right Place". In the section for Plants Suitable for Heavy Clay it lists the following (I will only list the larger plants):

They are talking about "a slab of clammy clay". It says these plants (and all plants) prefer a better situation but that these will grow in such conditions.

Quercus (Common Oak) 60 - 90ft.
Chamaecyparis (Threadleaf False Cypress) 60ft.
Cercis (American Redbud) 25ft.
Viburnum 'Lanarth' (Form of Japanese Snowball) 6 - 10 ft.
Weigela 'Bristol Ruby' 5ft
Aesculus x carnea 'Briotii' (Form of Red Horse Chestnut) 35 - 50ft.
Cratagaegus oxyacantha (Form of Hawthorn or May) 15 - 20 ft.
Spirea x arguta (Bridal Wreath) 6 - 8 ft.
Eupatorium purpureum (Joe Pye Weed) 4 - 6 ft.

If you do try the Robusta Junipers, I would suggest digging out and removing the existing soil in a good sized planting hole and replacing it with sandy loam. That would be a lot of work but I think you will just end up loosing these like the others if you try the same thing over again.