crikey man.. no tree is going to break into a gas line.. and steal your gas ... trees will take advantage of a pre-exisiting problem.. lets say an already crumbling foundation ... but they can not attack something that isnt already a problem ... if in fact you end up with a gas leak.. then you will have a problem... but it will not be for any trees to have caused it ... now ... lets talk about what you mean when you say mid sized ... no tree really ever stops growing.. if it does.. its dead ... so what you need to key in on.. is annual growth .... if it grows a foot per year.. in 20 years.. it should be 20 feet tall ... if it grows.. like some poplars.. 5 feet per year.. we are talking 100 feet in the 20 ... so when you are looking to Id any tree... try to find out how much it grows per year.. and work from there ... use of latin names and a search engine can usually get you that info ... as to either of your choices in UT.. i have no clue ... hopefully others will help you there .. but if not.. try calling your COUNTY extension office.. and asking about good trees for you COUNTY . good luck ken

Looking at your photo I'd guestimate your front yard area to be about 30' x 50'. Is this picture shot in the morning. If so then afternoon shade will come from this tree, right? I'm a big fan of Maples for fast growing. Most big shade trees will grow 50'-100' high by 40'- 60' wide. If you look at your photo you see your neighbor maybe 3 houses down with a full grown tree. That's what 1 tree will look like in 20-30 years. Across the street on the curve is what 2 or more trees will look like. My preference would be like your neighbor on your side of the road, That spacing gives you a lot more edges that are not shaded entirely by the tree. My sister lives in a neighborhood that has tons of full grown trees and her house always seems dark on the inside to me. I moved into a home that only had bushes 4 years ago I planted an Acer freemanii October Glory because of it quick early growth. I planted it from a 5 gallon pot. It was only 6' tall and now it's about 15'. I expect to get shade from it in another 10 years. Most of my work was done in California near Sacramento. Because of space expenses they grow their trees in pots. Here we have space and tree farms are the norm. I have a friend who has a tree farm that I drive by often on my way to St. Louis. He removed a line of evergreen trees that were doing poorly and replaced them with Maples. They looked to be 1 1/2" -2" size. Because of his having to water them from transplanting about 6 out of 15 died. My point is that field grown trees have their roots well away from the trunk so there's plenty of transport shock. Bigger may not be better in this case. Quercus coccinea or Scarlet Oak has beautiful fall color where the evening temps are low in fall. They are NOT as fast growing as the Maples. 60'-80' high by 40'-60' wide. What ever you do plant do yourself and the tree a favor and keep a 6' planting space. This keeps the lawn mower and string trimmer well apart. I also would plant it slightly elevated say 6" to allow for settling after transplanting. This also allows good water drainage. Remember the people who plant it do what YOU tell them if you tell they what you want.

I do LOVE my red push pistache and I recommend them to many clients who want a beautiful shade tree. I do not think they are messy. Of course they go dormant so you need to be ok with no leaves in the winter. But each tree will act different depending on the temp where it is planted. I saw 2 today full of leaves! The pistache requires more water than our desert trees. The difference with the citrus is that you will want to do deep watering often in the summertime. You must be careful though and make a well around the trunk as you do not want the citrus trunk to ever get wet. You also want to fertilize the citrus and be sure to paint the trunks in the spring so they do not get burnt in the summer. I would stay away from the sissoos. Once you have them they will spread roots looking for water. If they reach grass you can bet on little babies popping up everywhere! I am an arborist and I cannot tell you how many we have removed in the past 5 years. Once removed none of the root system can have any water or sunlight or you will be sure to have babies everywhere. You definitely have room for the swan hill olive (fruitless variety) and I agree that they are super clean. They will send suckers up at the base all the time and you will want to cut these back. I really like the tipu tree also. It does get very large, has beautiful leaves and small yellow flowers. it will defoliate late winter and immediately send new leaves out again. Below is a baby and a close up of the leaves. I was really glad to see you have the trees spaced far apart. So many times trees are planted too close and end up competing for sun. I hate removing trees for this reason. Good luck!

No, I am still here. Thanks guys for your all suggestions replies. To be honest I am more on the side of Photinia than on Camelia. It is hard to say, they have never saw any blooming on those trees and leaves do look red . But in any case I think they will keep those trees for now, they will trim but that bush (as kiminpl called blob) they probably will remove it and plant small tree as Yardvaark(9A) mentioned. Yardvaark(9A) Thanks for your design and suggestions. We like the idea of multi-trunk tree in front of the blank wall. As biondanonima said it is weird layout. The walkway leads to the driveway/garage that's correct. So thats why there are no reason for them to walk directly out the door and out to the street. And that's why they don't need walkway from the sidewalk directly to the front door. So the idea is to make this entrance more closed from the public. To plant plants in order cover the ugly layout and huge wall, make some privacy. Because the entrance is facing the main road and it is a corner house. There are used to be two huge oak trees in front of the house. When they moved in they had to cut it because they were dead. Thats why that wall look very weird. Here is the picture from 2008. Here is the picture from 2016, you still can see sign on the grass from oak trees I probably should have mention that this is corner house and facing main road. But the real entrance leads from driveway. One more picture: