Lake Forest Beach is right next to the Tahoe City Coast Guard Station. From the parking area, head straight out to the lake. You will see the peninsula (if it isn't under water) where the lupine grow.
The lupine grow best in this area on low lake level years. When the lake is higher, this area is under water.
"Tahoe Lupine at Night 3" - Photograph of flooded lupine wildflowers at Lake Tahoe. Shot at night, the Milky Way can be seen in the distance.