Here is a close up of the available room the trunk would have before it would reach the end of the flat area of where it was planted.

Wow. How big of a hole did you have to dig? Tall transplant. Lots of stakes but then again I do small transplants and don't know your cultivar.

IMO the tree will never be concerned with that lil bump downhill towards the fence. MAYBE a Liriodendron tulipifera, tulip tree, or a Populus deltoides, eastern cottonwoodn could expand its trunk almost to your fence in a lifetime.

i think your bigger concern... is how you are going to keep the root mass planted.. damp for a year or two ... on a hill like that ... how will water soak in.. before it moves away ...

think about some retaining wall blocks out about 4 feet....and back filling it .. to make a flat surface ... and then adding the mulch that is supposed to be there ... ....

refer to link.. and lets talk about anything you did.. that varies vastly with such ... and do see if you can find the root flare ...

the trunk will get.. as big as it gets.. before the tree dies ... i dont really know what you are getting at... with the way you ask the question ...

the tree .. if it lives.. will acclimate itself to the soil .... and all you can do.. is insure it doesnt wash away ... like using the blocks ...

ken

Here is a link that might be useful: link

Is this what you are worried about? The huge Quercus robur trunks? Is that the "parent" of your cultivar?

I think if I was moving in 80 years from now and there was an oak threatening the fence I would happily deal with it.

How old is that royal prince cultivar? If the "type" tree is only 40 years old then we might not know its typical mature trunk.

I'd clear out some of that grass, put a mulch down, and forget about it. The mulch will prohibit erosion. Everything is fine with your Oak.
Mike

IMO its as simple as Mike's answer.

Wow, thanks for the replies. I've checked with the owner of Mid Valley Trees and he stated the trunk should max around 12" or so. He also looked at the pics and told me I should be fine just as it is. My concern was the tree's trunk and root system running out of growing space of the sloping area between the tree and the fence. As far as water goes I have that entire mound on a yard sprinkler system and can easily control the amount. Erosion is a concern and I am going to plan on adding lawn fescue through that area of concern. Making sure in keeping enogh top flat area for the root ball to breath and having growing room.

The tree is a 15 gal and I have to give credit to Mid Valley Trees for they have big healthy trees! Thanks Brent. The tree is a regal prince oak and supposed to get around 45-60x 15-20. We shall see....

Support poles are a must for through spring and early summer we seem to have a constant wind from the North West blowing South Easterly which tends to pitch newly planted trees. I triangulate the tree with the support poles. This tree is a especially tall. I'm hoping ths year mother nature skips this years season of winds.

Thanks again for the reaponces!

A slope like that is nothing.

Narrow growth habit so close to neighbors is a wise choice.

This post was edited by hoovb on Sun, Nov 16, 14 at 2:01

I've added a little more dirt and broadened the top flat area. I plan on adding a little more dirt to have it flow a tad more and then adding some lawn fescue to help hold the slope from erosion during waterings. Here's a pic of the added dirt which I'll still will work a bit to make it flow..... more smoothe natural looking....

Here we go. Just a little fine tuning left. Whew!

Thanks for the update Dmacsimus, how has your weather been?

congrats.. looks great ... ken