Question: What is the total number of Yellowstone National Park's trees and vascular plants?
About the article "Yellowstone National Park", section "Flora".

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Over 1,700 species of trees and other vascular plants are native to the park.
Another 170 species are considered to be exotic species and are non-native.
Of the eight conifer tree species documented, Lodgepole Pine forests cover 80% of the total forested areas.
Other conifers, such as Subalpine Fir, Engelmann Spruce, Rocky Mountain Douglas-fir and Whitebark Pine, are found in scattered groves throughout the park.
As of 2007, the whitebark pine is threatened by a fungus known as white pine blister rust; however, this is mostly confined to forests well to the north and west.
In Yellowstone, about seven percent of the whitebark pine species have been impacted with the fungus, compared to nearly complete infestations in northwestern Montana.
Quaking Aspen and willows are the most common species of deciduous trees.
The aspen forests have declined significantly since the early 20th century, but scientists at Oregon State University attribute recent recovery of the aspen to the reintroduction of wolves which has changed the grazing habits of local elk.
There are dozens of species of flowering plants that have been identified, most of which bloom between the months of May and September.
The Yellowstone Sand Verbena is a rare flowering plant found only in Yellowstone.
It is closely related to species usually found in much warmer climates, making the sand verbena an enigma.
The estimated 8,000 examples of this rare flowering plant all make their home in the sandy soils on the shores of Yellowstone Lake, well above the waterline.
In Yellowstone's hot waters, bacteria form mats of bizarre shapes consisting of trillions of individuals.
These bacteria are some of the most primitive life forms on earth.
Flies and other arthropods live on the mats, even in the middle of the bitterly cold winters.
Initially, scientists thought that microbes there gained sustenance only from sulfur.
In 2005 researchers from the University of Colorado at Boulder discovered that the sustenance for at least some of the diverse hyperthermophilic species is molecular hydrogen.
"Thermus aquaticus" is a bacterium found in the Yellowstone hot springs that produces an important enzyme (Taq polymerase) that is easily replicated in the lab and is useful in replicating DNA as part of the polymerase chain reaction (PCR) process.
The retrieval of these bacteria can be achieved with no impact to the ecosystem.
Other bacteria in the Yellowstone hot springs may also prove useful to scientists who are searching for cures for various diseases.
Non-native plants sometimes threaten native species by using up nutrient resources.
Though exotic species are most commonly found in areas with the greatest human visitation, such as near roads and at major tourist areas, they have also spread into the backcountry.
Generally, most exotic species are controlled by pulling the plants out of the soil or by spraying, both of which are time consuming and expensive.
 "Field key to the flora of Yellowstone National Park, WY".
1975, Yellowstone National Park: Yellowstone Library and Museum Association.
"Fire as an ecological force in Yellowstone ecosystems" (Information paper / Yellowstone National Park) "Yellowstone vegetation: consequences of environment and history in a natural setting", 1990.
Boulder, CO: Roberts Rinehart, Inc. "Plants and their environments: Proceedings of the first biennial scientific conference on the Greater Yellowstone Ecosystem", 1994.
Denver, CO: National Park Service.  
The Grand Canyon of the Yellowstone is the first large canyon on the Yellowstone River downstream from Yellowstone Falls in Yellowstone National Park.
The canyon is approximately long, between deep and from wide. 
Yellowstone National Park is home to four amphibious species and six species of reptiles.
None of the species are endangered or threatened.
The glacial nature of and dry conditions in Yellowstone are likely responsible for the relatively low number of amphibian and reptile species in Yellowstone. 
Christmas in August (formerly known as "Savage Christmas") is an annual tradition in Yellowstone National Park.
The celebration includes decorating Christmas trees, singing Christmas carols, and gift exchanges.