Ask Mr. Smarty Plants

Pinus nigra, Austrian pine, in native to (among other countries) Austria and Switzerland, and therefore is out of our range of expertise. At the Lady Bird Johnson Wildflower Center we are dedicated to the care and propagation of plants native not only to North America but to the area in which they are being grown. What was your landscaper's reason for recommending that particular tree? When we looked at the USDA Plant Profile for the Austrian pine, it was not even shown as growing in Colorado or, indeed, anywhere close to it. It grows mostly in the Northeastern United States and in Eastern and Western Canada. It is hardy in USDA Hardiness Zones 4 to 7, and Denver is apparently between Zone 4b (average annual minimum temperatures of -25 to -20 deg. F) to 5b (-20 to -10), so it could survive on that account. It can apparently be subject to some insect and disease damage, and we would be concerned that something against which that particular tree had no defenses would attack it. We also learned that it grows to 60 ft. and a 20 to 40 ft. spread. That doesn't sound much like a tree for a small yard, does it? Pictures of Austrian Pine.

Obviously, we would prefer you use a tree native to Colorado, and since you mentioned Mountain Mahogany, we checked on that. There are three native to Colorado, but only one, Cercocarpus montanus (alderleaf mountain mahogany), is shown on the USDA Plant Profile as growing in the Denver area. It is  8 to 12 ft. tall, low water use, sun, larval host to Mahogany Hairstreak butterfly, also cover and nesting site for birds.

Since you were interested in the genus Pinus, the Austrian pine, we looked at some members of that genus native to the Denver area:

Pinus contorta (lodgepole pine) - grows quickly to 20 ft., may reach 30 ft. at maturity, medium water use,sun. Larval host for Western Pine Elfin Butterfly. USDA Plant Profile More Pictures

Pinus edulis (twoneedle pinyon) - 10 to 30 ft., low water use, part shade,  USDA Plant Profile

Pinus flexilis (limber pine) - 30 to 60 ft., low water use, sun, part shade, USDA Plant Profile  More Pictures

If you are really interested in maintaining a native habitat, hopefully you can find a tree among these selections that will work for you.

Cercocarpus montanus

Pinus contorta

Pinus edulis

Pinus flexilis