Description of Poplar clones

Poplar is one of the best known, most widely distributed trees in Canada. Native stands of trembling aspen and balsam poplar and plantings of plains cottonwood have provided shelter for innumerable farms throughout the prairies. Poplar selections have also been introduced from Europe, eastern Canada and the United States but most have not proven hardy enough for prairie plantings.

Hybrid poplars are crosses between native selections and/or introduced species which have been shown to exhibit superior traits. Hybrid poplars are produced vegetatively, resulting in uniform stands on sites with good growing conditions.

Poplar is most commonly used to provide quick summer shelter in farmstead belts but is not used for roadside or field belts because of its competitiveness and generally short life span.

Poplar grows very rapidly, reaching a height of 6.5 metres in 7 to 8 years. The crown shape varies with different clones, but generally is very loose, providing little winter protection. Under arid conditions they are short lived (20 to 25 years) while under moist conditions they may reach 20 to 24 metres and survive 50 to 60 years. Roots are shallow and may spread 15 to 20 metres away from the tree. Poplars are susceptible to iron chlorosis in soils where availability of iron is limited.

The leaf forms of hybrid poplar are not good criteria for distinguishing between species or clones since leaves often vary in size and shape with site and age of the specimen.

Male and female flowers are borne on separate trees. Female clones produce an abundance of cotton which may be undesirable in building areas or near dugouts.

The PFRA Shelterbelt Centre produces four hybrid poplars:

• 1.Walker Poplar: This clone was selected from open-pollinated seedlings of Populus deltoides by John Walker at the PFRA Shelterbelt Centre in Indian Head, Saskatchewan. Walker is our most vigorous clone with a growth rate of 1.3 metres per year. It has a narrow crown and is usually single stemmed. It has shown resistance to leaf rust, canker, and poplar bud gall mite though it occasionally shows winter injury. Walker is a female clone producing seed cotton every year after it reaches maturity.
• 2. Assiniboine Poplar: This clone was selected from an open-pollinated stand of Walker poplar at the PFRA Shelterbelt Centre. Assiniboine has a rapid growth rate reaching 7 metres after five years in tests at Indian Head. It has a fairly narrow crown. Other favourable characteristics include good winter hardiness, resistance to insects and disease and a moderately branched growth form. Because it is a male clone it will not produce seed cotton.
• 3. Manitou Poplar: This clone was selected from open-pollinated seedlings of Walker poplar. It is a fast growing tree, resistant to poplar bud gall mite and Septoria canker, and completely winter hardy. Manitou is a large, heavily branched tree and is much wider than Assiniboine or Walker. It roots easily from hardwood cuttings and because it is a male clone it does not produce seed cotton.
• 4. CanAm Poplar: This clone was selected from open-pollinated seedlings of Walker poplar. It is a fast growing tree, resistant to poplar bud gallmite and leaf rust. It also has superior resistance to winter damage. CanAm has a narrow, upright crown with the branches angled sharply upward. It is a female clone and therefore produces seed cotton at maturity.

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