In the spring Columbia Hills State Park is a wildflower haven, with many trails to experience these beauties from. One option is Crawford Ranch where it is possible to do a 3.4 loop by starting from the Dalles Mountain trailhead parking area (directions described below).
From the trailhead, hike the Pond Connector Trail, taking a left on the Ranch Route Trail then a right onto Military Road and another a right when you reach the intersection with the Eight Mile Creek Trail. This completes most of your loop, you just have to take a left when you reach the Pond Connector Trail again and you'll be on the way back to the parking area.
A map at the trailhead, near the outhouse shows the various trails and their mileage.
WTA Pro Tip: If you have 2 vehicles, you can park one at the Crawford Oaks trailhead, and do a thru-hike.