I don't recall the official name of the items, but they are a plastic mesh, expandable tube that is placed around the tree at planting time. In our case, we are usually planting doug fir, red cedar, redwood and hemlock.
The saplings, usually from 18" to 24" in length are placed in the protective plastic sleeve. The tree is planted through a slit in a four buy four biodegradable plastic ground cover that is stacked down with approximately 6inch long metal staples (4 staples per tree). The ground cover keeps the competition with other plants directly around the tree minimal and the plastic mesh, expandable sleeve protects the young trees from the browsers, usually deer. Within three years the ground cover has disintegrated and disappears. The mesh, expandable sleeve is moved up the tree as it grows to protect the new growth foliage. Within four to five years the sleeves biodegrade and fall off of the tree, which is usually tall enough and large enough to withstand the attack of the deer and other browsers by that time.
Some trees receive damage to the point that some are stunted to a degree. If we experience tree loss during their early years, the loss is usually more than likely due to lack of moisture, years where things get too dry in late August and into September.
This planting technique does not solve all of your problems, but if your are located in the rain forest north west region, we have had very good results using the described planting process.
Nick, North West Farmer