Mount Si via the back way. Begin from the large Mount Teneriffe parking are and add on some miles to sneak up this popular peak from behind.
From the parking area, we'll start out on the Mount Teneriffe trail, a road-to-trail conversion that offers gorgeous lush forest, and a pleasant, almost flat walk for the first 1.5 miles, before getting down to business and climbing in earnest for the next 2.7 miles. Luckily, the views along the way are quite good, so you have plenty of opportunity to stop and enjoy them (while catching your breath, of course).
Notable views through this steep old road include Mount Rainier and Rattlesnake Ledge. .
At a 'T' intersection 4.2 miles from the trailhead, make a left at a junction marked with a trail-network sign. Turn left, and we'll continue to climb for about 0.4 miles through rolling forest before reaching a high point. Through here, be sure to stop and look up. We'll have a view of Mount Si most hikers never see. On this same section of trail, look north along the Puget Sound coastal plain to see Mount Baker and, on a clear day, all the way to Whistler Mountain in British Columbia.
Soon, we'll descend the final 0.4 miles to the base of the haystack on Mount Si.
We'll pause for a quick summit lunch and take in the views.
Then we'll head down the Mt. Si main trail and finish via the lower Talus Loop Trail.