Pyrus calleryana, or 'Chanticleer' Pear is a highly rated tree for the Front Range due to its drought tolerance, adaptiveness to alkaline soils and a wide range of soil types. It is a smaller tree with a pyramidal, upright shape with a height of 25 feet and width of 15 feet.

Acer x freemanii 'Celebration' or the Celebration Maple has a columnar shape and reaches 45 feet tall and 25 feet wide. Freemanii maples are hybrids of Silver and Red Maples, and do tend to have problems with iron chlorosis in alkaline, heavy clay soils.

A rule of thumb is to plant trees a distance equal to at least 2/3 of their mature height from any structure. In the case of the Chanticleer Pear, it should be at least 17 feet from the house; the Celebration Maple at least 30 feet. See this link for more information on tree placement:

http://planttalk.colostate.edu/topics/design/1120-tree-placement-tips/

Tree root systems extend about one to 1-1/2 feet out from the trunk for every inch of trunk diameter. A 12-inch diameter tree will have roots about 18 feet in all directions. Tree roots will grow anywhere there is uncompacted soil and oxygen, which includes under a driveway and sidewalk. Here is some additional information on trees and their roots.

http://extension.colostate.edu/topic-areas/yard-garden/healthy-roots-and-healthy-trees-2-926/

Here is a good article on tree roots, driveways and sidewalks.

http://www.gfc.state.ga.us/community-forests/ask-the-arborist/treeroots-driveways-sidewalks.pdf

It appears the Celebration Maple is not the best choice, nor in the right place. You didn't specify how large the maple is, but digging up a tree that has been in the ground with the intention of trying to save it can be a challenge. This is best done in early spring before it leafs out. Water well from the trunk to the dripline the day before digging. Dig as much of the root ball as possible (at least 90-95% retention), and wrap the root ball and keep wet or have the new location ready to plant.

Not knowing how much space is available between the house / driveway / park tree, it is difficult to recommend a specific tree. It would also depend on how large the nearby oak tree would get.

Here are some links that would assist you in picking a smaller/upright tree or columnar evergreens. You may also consider shrubs since the space is smaller.

http://extension.colostate.edu/topic-areas/yard-garden/small-deciduous-trees-7-418/

http://extension.colostate.edu/topic-areas/yard-garden/evergreen-trees-7-403/

http://extension.colostate.edu/topic-areas/yard-garden/deciduous-shrubs-7-415/

Here is the Front Range Recommended Tree List. Pay close attention to the rating and the comments:

http://extension.colostate.edu/docs/pubs/garden/treereclist.pdf

If your drawing is indicative of mature size, then the Red Oak and Celebration Maple are a problem. If HOA requires two trees in the front yard, then a shrub may not be the solution unless the HOA would approve a deviation due to the size of your lot.

You might consider in place of the Celebration Maple an upright or columnar tree such as:

Columnar Mugho Pine (6 foot wide)

Columnar Blue Colorado Spruce (6-10 feet wide)

Crimson Spire Columnar Oak (10 feet wide)

Kindred Spirit Columnar Oak (7 feet wide)

The Crimson Spire Columnar Oak is highly recommended and proving to be an exceptional tree with few problems and beautiful fall color. It is a marcescent deciduous tree, so it does not shed its leaves until the spring. None of these trees should be a problem planting in the closer proximity to the driveway.

You didn’t mention why you are choosing to remove the Hackberry. It’s a highly recommended tree for the Front Range and is grown for its beautiful foliage. They generally grow with upright branches and is a good tree for drought conditions. It does get red fruit in the fall, and is one of the slowest growers of trees in Colorado. It is wind and snow tolerant. It can be limbed up should you need to walk under it. There are several varieties so it may not get as tall as a common variety at 50 feet. It looks like it would be a nice shade tree for the front of the house. Might you consider leaving it?

If you are wanting to plant something smaller, try to avoid the Chanticleer Pear. Overuse of a single type of tree should be avoided in neighborhoods; especially in side-by-side trees. It’s important to focus on tree diversity. Smaller trees to consider would be:

http://extension.colostate.edu/topic-areas/yard-garden/small-deciduous-trees-7-418/

Serviceberry

Hawthorns

You could go with medium size trees that are on the lower range of height (30 feet tall)

Linden (many varieties to select from)

Ohio buckeye

Thinleaf alder

Some small to medium underused trees that are successful in the CSU Arboretum Plant Trials:

Coralburst Crabapple

Curleaf Mountain Mahogany

Homestead Buckeye

Katsuratree

Manzano Bigtooth maple

Peking Lilac

Prairie Gem Ussurian Pear

I was very excited when you suggested a columnar mugo pine in place of the Celebration Maple. I love mugo pines and did not know there was a columnar variety. However, my research said that they need full sun, which I know is 6 or more hours, and I don’t think the area where it would be planted gets that much sun. Additionally, the red oak in the park next to us will eventually shade even more of the area as it matures.

The Columnar Blue Colorado Spruce might be the better option as it can take partial sun. I will monitor the location some more.

As far as the Western Hackberry, I did not know there are smaller varieties of it as well. I do not know which variety our is, the label just says, ” Western Hackberry.”

It appears the smaller variety of Western Hackberry trees reach 20-30 feet tall. At 30 feet tall, and using the rule of thumb that you taught me, that means it should be planted 20 feet from the house. I do not have that much distance in my front yard. I also do not care for the nipple gall that they are very susceptible to getting.

I will research some of the small to medium tree varieties that you suggested.

Thank you again for sharing your expertise.

Just a note on the 6 hours of sun. It does not have to be continuous. It can get 3 hours in the morning and 3 in the afternoon. Or 4 morning/2 afternoon. Etc. Also, if it can receive the 6 hours of sun while it is getting established for the first several years, it would likely be able to handle slightly less sun as it grows to maturity. You are wise to monitor the area first to determine how much sun it truly does receive.

The Hackberry is such a great tree for our area so it's difficult to see when they have to be removed. Your concerns about the proximity to the house and the nipple gall are certainly valid; I'm sure there are some other trees that you ultimately might be more satisfied with.

If you have additional questions, please let us know.

Hours of sun refers to direct sunlight (rays) on the plant.

 Donnetta,

I am very attracted to the Bigtooth Maple to replace the Western Hackberry tree in our front yard, due to its size, fall colors, and high recommendations. However my concerns are the lower moisture requirements, our soil type, and the planting distance from our house.

The proposed planting site:

·      Is in a bluegrass lawn area; although, it is 3.5‘ from a xeric shrub bed in rock mulch, 7.5’ from a rock border and driveway, and 6’ ft. from the city sidewalk and street. So once it matures, many of the tree’s roots would probably be exposed to less moisture. (See attached scale drawing, drawn with the Bigtooth Maple at 20’ diameter.)

·      Has a soil PH of 8.4 & clay loam soil. (I just had CSU test it.)

·      Can’t be more than 10 feet from our house due to the city's 6-foot easement along the sidewalk.

·      Is on the north side of our house, in our front yard where it will receive some protection from wind for most of the year. 

·      Will receive full sun. 

·      We do have deer in our area; however they tend to hang out in the open space behind our back yard.

Do you think this would be a suitable tree in our planting location?

If it is a possibility, is there anything we can do to improve its success?

Big Tooth maple (Acer grandidentatum) is a native Rocky Mountain species that tolerates alkaline soils. Plant in well-drained soil, and once established it is drought tolerant. The Big Tooth maple is considered a small tree and offers beautiful shades of yellow, orange, and red in the fall. Because of its smaller size, it is great used as a specimen or in a smaller or confined area in the home landscape. It has a slower growth rate, maturing at approximately 20 feet tall by 15-20 feet spread.

This would be a good tree for the location you describe. Make sure to amend the soil 5% before planting. Amending the soil with sphagnum peat moss may help somewhat with the soil pH. Any new plant requires additional watering until established. For trees, a 1-inch diameter tree typically takes 1 year for roots to establish. Once established, however, the drier soil and xeriscaping should not be a problem.

The Front Range Recommended Tree List rates it at an "A" with a notation of limited availability. If you are purchasing and planting yourself, call local nurseries to check for availability. The most important factor for successful trees is correct planting. Here is a link for tree planting:

http://static.colostate.edu/client-files/csfs/pdfs/TreePlanting_636.pdf

Big Tooth maple (Acer grandidentatum) has been a test tree in the CSU Arboretum where they have much more detailed information about its growth habits and other pertinent details. Consider contacting the arboretum staff to obtain their scientific observations and trial results. They may also have more information on Acer grandidentatum 'Manzano'.

http://landscapeplants.agsci.colostate.edu/arboretum/.