Sunday, November 7, 2010

Tree of the Week - Hybrid Poplar

I figured I'd change it up a bit this week and go for a tree with amazing growth characteristics; the hybrid poplar; which is the result of crossing aspen, cottonwood and poplar species. These trees are capable of growing upwards of 8 feet in height per year; adding over an inch in diameter in ideal locations. The great news is, hybrid poplars are able to grow virtually anywhere; there are so many varieties out there that are adapted to warm or cold, wet or dry climates that there is virtually one for everybody.

I wanted to spend some time talking first about the primary uses of hybrid poplars. For the most part; hybrid poplar is used for two main purposes in the United States; biomass fuel and pulp wood (for the paper industry). It is also utilized overseas in Europe as lumber and engineered wood products. Virtually any land owner can benefit from planting poplar and the great part about it is that it can be beneficial to those who even own only a few acres.

For homeowners with small tracts of land (1-5 acres) that heat with wood, hybrid poplar is a great way to become self-sufficient. Hybrid poplar can be planted on a 6'x6' grid on an acre of land, with 1,200 trees per acre and will provide upwards of five cords annually per acre after the first succession, which will yield two to three cords annually. To establish such a plantation, there are four successive plantings; each 1/4 acre, spaced one year apart. By the fourth year; the first planting will be 20 to 30 feet tall and approximately 4" in d.b.h; at which point it can be cut into usable fuel wood. On the fifth year, the second 1/4 acre will be harvested, and so on. It is important to note that hybrid poplar has a much lower BTU/cord content because of its relatively light weight; thus it is equivalent to around 1/2 of standard hardwood firewood; i.e. it would take two cords to produce the heat output of one cord of quality hardwood.

If planning to grow for longer periods of time; trees need more growing area. A six year rotation will require an 8x8 plot or 680 trees per acre; while an 8 year rotation will require spacing of 9x9 or 520 trees per acre. An eight year rotation will produce approximately 45 cords per acre; or 5.7 cords per year (averaged over 8 years). A six year rotation will produce only 25 cords at only 4.2 cords per year; while a four year rotation will produce approximately 15 cords at 3.8 cords per year. Clearly, if you're willing to wait; the payoff is dramatically increased; as the IRR is lowest for a four year rotation and highest for an 8 year rotation over a 35 year growing period.

One of the benefits of the hybrid poplar is its ability to regenerate from its stumps when young; meaning that after the first harvest, the trees will quickly produce new growth and will be able to be harvested in another four years with an even higher yield. The trees will last for upwards of 35 to 40 years before losing vigor; meaning that you can expect multiple harvests from the same planting. However, if harvested in intervals greater than eight years; stump regeneration is often less reliable. Thus, to save the cost associated with planting; poplar should be harvested on at the very longest; an eight year schedule. At that length, the wood may also be marketed to log buyers as pulpwood for the paper industry; if, of course, there is a buyer in the area.

A short to medium-term rotation poplar plantation is also a great wildlife tool; as it will have various tree age classes; providing browse and cover for a variety of wildlife. Further, deer love hybrid poplar. While this would be a concern with the planting of other species; the rapid growth of hybrid poplar ensures that the trees will be well beyond the point of deer browse after a couple of good growing seasons. Of course, large scale planting will reduce the effects of browsing as well. Hybrid poplar would be a great choice for a land manager that has a mostly pole-sized forest but wants to provide some thicker cover for wildlife while the poles develop. By dedicating a portion of the property to hybrid poplar production, land managers can achieve this goal by planting on a four, six or eight year rotation, while also being able to generate income in a few short years.

Hybrid poplar is readily planted as unrooted cuttings, which makes planting it much less time consuming than other tree species which require rooted seedlings. It rapidly sends out roots provided moisture and proper growing conditions. The selection of the proper clone for your area is key to the success of the plantation. Further, one should consider planting multiple varieties to reduce the risk of insect or disease infestation throughout the entire plantation, or, at the very least, planting disease-resistant varieties.

Overall, hybrid poplar is a unique option for some land managers. It's fast growth and ability to regenerate are great assets that may be exploited with great success in certain applications.

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