The Winchester willow on the shore of Upper Mystic Lake in May Apex of a fallen twig Closeup view of leaves Pistillate catkin Adventitious roots starting on a twig Rooted twig with a developing bud
Salix × meyeriana from Winchester
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Willows of Massachusetts:
Salix × meyeriana Rostk.
(= S. pentandra × S. euxina) found
in Winchester, eastern Massachusetts

An Eurasian willow Salix pentandra L. has been erroneously reported from New England. The majority of North American samples identified as S. pentandra I examined at the Harvard University Herbaria and other herbaria appear to be hybrids of S. pentandra with S. euxina Belyaeva (S. fragilis auct., part.) known under the name Salix × meyeriana Rostk. ex Willd. [1, 2, 3]

According to the treatment of willows in FNA (Argus 2010), "S. pentandra" introduced to North America has been known only as pistillate plants. A plant currently cultivated under the name of S. pentandra at the Arnold Arboretum is also a hybrid of S. pentandra, though reperesenting a different, staminate clone [2]. Recently I have discovered a pistillate living specimen of S. × meyeriana planted at a private property on the shore of the Upper Mystic Lake in Winchester, Middlesex County, Massachusetts. This is a large tree (83 cm DBH). According to the owner, this willow is more than 50 years old. It was purchased at a local nursery and planted in the early 1960's.

There are no branches within reach, readily accessible for examination; however, one can find some dropped twigs on the ground. Freshly dropped ones are capable of producing adventitious roots when put in water—a feature characteristic of S. euxina or S. x fragilis L. (in S. pentandra twigs are not brittle, and one should not expect finding many on the ground). Even though the leaves of the Winchester willow are broad and shiny, like those in S. pentandra, stipules are developed better (at least in young leaves); catkins are loose; and bracts exhibit long white hairs.

Examined herbarium samples of S. × meyeriana from eastern Massachusetts

A few of listed samples are definitely originating from cultivated plants; samples from Cambridge (1975) and Brookline (1901-1903) could originate from naturalized plants; as for those trees growing around ponds and at roadsides, it is difficult to say if they escaped from cultivation or were planted.

The available material provides no evidence that true S. pentandra has ever been introduced to New England—even though reliable identification of willow hybrids based on dry material is rather difficult and may not be always possible, particularly in this case. A series of herbarium samples by a single collector from Brookline and another one from Ipswich appear to be collections from the same tree (or at least the same population) at different seasons. Both series, and particularly the one from Brookline, allow the most confident identification S. × meyeriana. A single specimen of "S. pentandra" from Nantucket Co. (Nantucket, July 21, 1943, R.C. Bean, NEBC) has not been included in the list above. It may as well be S. × meyeriana, though due to insufficient collection cannot be identified properly.

It should be noted that the application of the name 'meyeriana' to these hybrids is largely arbitrary: it is hardly possible to visually separate hybrids of S. pentandra and S. euxina from those of S. euxina and S. alba, i.e., with S. × fragilis, which may phenetically approach S. euxina. It is even possible that not all of New England plants resembling S. pentandra are actually pentandra hybrids. The native S. lucida has similar lustrous, usually broad leaves. If this North American willow has been able to hybridize with S. euxina or even S. × fragilis, the resulting hybrids might look similar to S. × meyeriana. However, the only known hybrids of S. lucida are those with S. alba, described as S. × jesupii Fernald. Even though S. × fragilis (S. alba x S. euxina) is not less frequent than S. alba, its hybrids with S. lucida are not known. One possible explanation is that such hybrids have just been overlooked—similarly to those of S. pentandra and S. euxina. One of those samples that may support this hypothesis is from Essex Co.: Middleton, Creighton Pond, 4 July 1957, S. K. Harris, 12895 (NEBC); others, even more suggestive, are from Deerfield, western Massachusetts. Among the examined samples of 'S. pentandra', there is only a couple of those that have been entirely misidentified. One from Adams, Berkshire Co., is actually S. lucida; two from eastern Massachusetts are rather typical S. × fragilis: Barnstable Co.: North Truro, Pond Road, Aug 1, 1973 H.E. Ahles 78110 (MASS); Dukes Co.: Naushan, Sept 5, 1928, John M. Fogg, Jr. 3873 (US).

A. Zinovjev 2011-06-02