Gertrude Lake Trail is a 8.3 mile lightly trafficked out and back trail located near Lower Forni, CA that features a lake and is rated as moderate. The trail is primarily used for hiking and is accessible from June until October.
Did this hike roughly two weeks ago. The gate to the Wrights Lake Recreation Area was already closed for the season, but you can still access the trails by parking at the gate and walking in. Because of this, there were very few people on the trails. Beyond the Rockbound/Tyler trail junction I had the trail completely to myself, and did not see anyone else the entire day.
The trail itself was fairly flat for the first 2-miles, with a couple decent uphill sections in the last couple of miles.
If you make to the hike to Gertrude, I would highly advise tacking on Tyler Lake as well. There is no established trail leading up to Tyler Lake (at least I didn't see one), but it is fairly easy to find. Just be mindful on your way back down as it is fairly difficult to retrace your steps.