The Puu Oo Trail is part of the Na Ala Hele trail system, and not to be confused with the Puu Oo Volcanic site in the Volcano National Park. The trail was, at one time, a cattle trail for moving cattle between two different grazing areas.
The trail runs alternately through recent and less-recent lava flows, and areas of forest untouched by the most recent lava flows. These islands of green and old-growth forest, or "kipukas," host a variety of birds and provide shade and respite throughout your hike.
There is a parking lot on south side of the highway between miles 22 and 23 of the Saddle Road. We did an out-and-back hike on the trail, although I understand there is a loop available that comes back to the highway on an old telephone pole road that runs back to the highway about a mile toward Hilo from the parking lot - you can hike back to the parking lot along the highway from there. The intersection to that trail (according to the park's website) is 3.7 miles out on the trail. We must have hiked out about 3.5 miles before turning around - never saw the trail.
Sections of the trail are lifeless like the moon, through the most recent lava flows. Other sections are sparsely wooded, and even look like an African savannah in places. Still other "Kipukas" are lush and green, full of tall, large trees, brush, ferns - and (I understand) pigs and sheep. We met a bow-and-arrow sheep hunter on his way out for a hunt. We saw signs of pigs rooting around in the dirt. But we didn't see either one.
There is a lot of up and down, but the trail doesn't head uphill or downhill - mostly across the saddle area between the two big volcanoes. Bring sturdy shoes for the lava rocks. Throughout most of the trail, the otherwise indistinct way is marked by cairns (locally called "ahu") of stacked rocks. In most places, the next ahu is visible from the last ahu. We were only briefly confused a couple times - but always found the next ahu before losing sight of the last. In other places, the trail is obvious and well trampled.
Interesting and rewarding hike for anyone who likes geology, birds, hiking, spectacular and distinctive vistas or just a fun walk in the woods/lava flows. read more