From the top to bottom of the forest here are some of the most commonly found and easy to identify flora growing in Peterson Creek in Kamloops BC. This article is a work in progress and updates are welcome.
Overstory/Canopy Layer
Ponderosa Pine
Douglas Fir
Black Cottonwood
Rocky Mountain Juniper
Russian Olive
Mountain Ash
Willow (various)
Maples (various)
There is one Hawthorn I know of in the park and a single horse chestnut.
Shrub Layer
Red Osier Dogwood
Saskatoon
Chokecherry
Pin Cherry
Snowberry
There are a handful of garden cultivars such as cotton easters and barberries that I assume have been ‘planted’ by birds.
Field Layer
Oregon Grape
Sagebrush
Rabbit bush
Alfalfa
Poison Ivy
Creeping Virgina
Deadly Nightshade
Honey suckle
Crested Wheatgrass
Ground Layer
Prickly Pear Cactus
Here is a lovely wildflower article from an avid local outdoor enthusiast.
Missing from this list are the arrowleaf balsamroot, gallardia, mariposa lilies and larkspur that are a less common sight due to people picking them.
Please do not pick wildflowers unless you know the FULL lifecycle of that plant.