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
The Nursery grows one of these poplars, clone number 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 eight to nine 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 15 years ago. 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 are about 10 years old. 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.
The T X M Crosses
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.
Phipps Nursery offers six different clones of T X M 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
Phipps Nursery grows two T X M X D crosses, 287-182 and 233-18; both very good clones but not tops in growth rate. Both clones' DBH at three 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.
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