From BiblePortal Wikipedia

Fausset's Bible Dictionary [1]

Used in constructing booths at the feast of tabernacles ( Leviticus 23:40). Spring up along watercourses. Spiritually it is thus made manifest to us that in using the means of grace the believer thrives ( Isaiah 44:4). The Jewish captives in Babylon hung their harps on the weeping willow along the Euphrates. The Salix Alba, Viminalis (osier), and Εgyptiaca are all found in Bible lands. Before the date of the Babylonian captivity the willow was associated with joy, after it with sorrow, probably owing to Psalm 137. Babylonia was a network of canals, and would therefore abound in willows.

The Jews generally had their places of prayer by the river side ( Acts 16:13) for the sake of ablution before prayer; the sad love streams, inasmuch as being by their murmuring congenial to melancholy and imaging floods of tears ( Lamentations 2:18;  Lamentations 3:48;  Jeremiah 9:1). Tear bottles are often found in the ancient tombs, and referred to in old inscriptions. The willow of Babylon has long, pointed, lance-shaped leaves, and finely serrated, smooth, slender, drooping branches. Vernon, a merchant at Aleppo, first introduced it in England at Twickenham park where P. Collinson saw it growing 1748. Another tradition makes Pope to have raised the first specimen from green twigs of a basket sent to Lady Suffolk from Spain (Linnaean Transactions, 10:275).

Easton's Bible Dictionary [2]

  • Heb. tzaphtzaphah ( Ezekiel 17:5 ), called by the Arabs the safsaf, the general name for the willow. This may be the Salix AEgyptica of naturalists.

    Tristram thinks that by the "willow by the water-courses," the Nerium oleander, the rose-bay oleander, is meant. He says, "It fringes the Upper Jordan, dipping its wavy crown of red into the spray in the rapids under Hermon, and is nutured by the oozy marshes in the Lower Jordan nearly as far as to Jericho...On the Arnon, on the Jabbok, and the Yarmuk it forms a continuous fringe. In many of the streams of Moab it forms a complete screen, which the sun's rays can never penetrate to evaporate the precious moisture. The wild boar lies safely ensconced under its impervious cover."

    Copyright Statement These dictionary topics are from M.G. Easton M.A., DD Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain.

    Bibliography Information Easton, Matthew George. Entry for 'Willows'. Easton's Bible Dictionary. https://www.studylight.org/dictionaries/eng/ebd/w/willows.html. 1897.

  • Smith's Bible Dictionary [3]

    Willows. Willows are mentioned in  Leviticus 23:40;  Job 40:22;  Psalms 137:2;  Isaiah 44:4. With respect to the tree upon which the captive Israelites hung their harps, there can be no doubt that the weeping willow, Salix babylonica , is intended. This tree grows abundantly on the banks of the Euphrates, in other parts of Asia as in Palestine.

    The Hebrew word translated Willows is generic, and includes several species of the large family of Salices , which is well represented in Palestine and the Bible lands, such as the Salix alba , Salix viminalis ( Osier ), Salix aegyptiaca .

    International Standard Bible Encyclopedia [4]

    wil´ōz ( ערבים , ‛ărābhı̄m ); ἰτέα , itéa (  Leviticus 23:40;  Job 40:22;  Psalm 137:2;  Isaiah 15:7;  Isaiah 44:4 )): In all references this tree is mentioned as beside running water. They may all refer to the willow, two varieties of which, Salix fragilis and S. alba , occur commonly in Palestine, or to the closely allied Populus euphratus (also Natural Order Salicaceae ), which is even more plentiful, especially on the Jordan and its tributaries. The Brook of the Willows ( Isaiah 15:7 ) must have been some stream running from Moab to the Jordan or Dead Sea. Popular fancy has associated the willows of  Psalm 137:2 with the so-called "weeping willow" ( Salix babylonica ), but though this tree is found today in Palestine, it is an introduction from Japan and cannot have existed "by the waters of Babylon" at the time of the captivity.