Washington State University's Experiment Station near Puyallup, Washington has conducted a breeding program to develop faster growing poplars for pulp production. The Nursery is growing genetically improved first and second generation poplar crosses developed at Puyallup. These improved poplars are offered in three groups based upon parents.
THE T X D CROSSES
The first group is similar to our original hybrid poplars being a cross between western black cottonwoods from the Pacific Northwest and eastern cottonwoods from various locations including Mississippi and Texas. These poplars are called T X D crosses or P. trichocarpa female parent and P.deltoides male parent. Original improved crosses were developed by plant breeders at Puyallup about 20 years ago. These poplars like neutral-alkaline deep river bottom soils.
Clone 11
It has been used by the James River Corporation for fiber farming near the Columbia River west of Portland. Clone 11 is somewhat rust tolerant but has limited resistance to canker and other foliage diseases. Considered a good growing clone but not as fast as newer crosses. Trees are considered suitable for pulp after 8 to 9 years. Clone 11 is characterized by small branches with a narrow crown( 20-25') compared to the broad crown of the old T X D cross(30-45').
Clone 50-194 and Clone 50-197
A slighty newer T X D crosses ( 50-194 and 50-197) were developed about about 1984. They share a common affinity of all T X D hybrids for deep river bottom soil with adequate summer water and neutral to slightly alkaline soils. Clone 50's has been shown to do well in Eastern and some parts of Western Oregon. It is tolerant of rusts in western Oregon and escapes the rust in Eastern Oregon. Vegetatative cuttings are all male and do not produce "cotton" or seeds in the spring. Of clone 50, clone 50-197 has performed slightly better than 50-194 in field trials.
Clone 15-29
Shortly after clone 50 T X D cross was produced, Puyallup researchers developed the 15-29 cross. It was found to have excellent growth and form. It also is capable of being planted widely throughout Oregon in proper poplar sites. It is resistant to rust diseases and tolerates foliage diseases. Early trials near Puyallup show clone 15-29 to be the top growing TXD cross at 13 inches diameter at breast height (DBH) in 3 years. Clone 15-29 is a female clone that will produce "cotton" or seeds at about age 6 or 7.
Clone 184-401 and Clone 182-187
The latest T X D poplar clones are 184-401 and 182-187 . Both were developed on or about 1990. Both are showing up as top growers with excellent rate of growth and form. Clone 184-401 and clone 182-187 are disease resistant. The parents of clone 184-401 are from higher elevation sources and hence is suited to higher sites throughout Western Oregon and all of Eastern Oregon. Clone 182-187 is suited to moderate elevation is Western and Eastern Oregon and it prefers warm growing conditions. Clone 182-187 is the earliest of the TXD crosses to break bud at Elkton so care should be taken to avoid early spring frost areas.
Foliage disease problems that affected the early hybrids bred at Puyallup led to a new parent selection to offer greater disease resistance. A Japanese poplar, P. Maximowiczii was found that had resistance to cankers and rusts. It was crossed with western black cottonwoods to produce a new T X M hybrid. This second generation hybrid is widely adapted to Oregon but since it has a tendency for early bud burst it may be prone to spring frosts. T X M clones have coarser branches than the newer T X D crosses. It is a fast growing tree with many clones equaling the rate of the better T X D crosses. Generally, TXM crosses perfer cooler growing conditions than TXD crosses.
Clones 265-28, 269-72, and 271-94 are recommended for western Oregon whereas clones 272-97, 263-12, and 262-8 can be grown throughout Oregon. The top rated growing clones of the T X M group are Clone 272-97 and Clone 265-28. All TXM crosses are resistant to rusts and venturia stem canker. Clone 271-94 and Clone 269-72 are the second earliest to break bud at Elkton. They can begin growth in late February and may be suspectible to early frosts.
The T X M X D CROSSES
Researchers at Puyallup also bred the Japanese poplars with T X D crosses to produce a hybrid with some of the better qualities of the T X D crosses with more disease resistance. These hybrids are better suited for more acid soils and more upland conditions with ample moisture. The T X M X D crosses share a common habit with the T X M crosses, i.e. early bud burst so frosts in spring can be damaging.
Clone 287-182 and Clone 233-18
Both very good clones but not top's in growth rate. Both clones DBH at 3 years is nearly equal to the older clone 11-11. However, TXMXD crosses are much more disease resistant than clone 11-11. Clone 287-182 is the first to break bud at Elkton in early February.
How do I chose what's best for me?
If you want to control erosion near streams or to grow wind breaks or wildlife trees most any poplar offered that is recommended for you part of Oregon will do the job. If you are interested in fiber farming or growing poplars as a plantation for pulp or fast firewood trees your choice is more difficult. Your decision may require a trial of several different clones to see which will do best on your property.
The Nursery will pack a special field test collection of 10 cuttings of each of the improved hybrids available. Please ask for the complete field test package. You may also can chose a special T Max sampler of 10 each of the 6 clones of T X M or a special T X D sampler of 20 each of the 4 T X D clones or a mix of 30 each of the T X M X D clones as the T X M X D sampler. Special mixes will cost more than a single clone order due to the increased handling required to custom pack your mix of poplars. After 2-3 years you can discover the best clones for your site, then order them in units of 50 or more cutting each.