NEW SOUTH WALES FLORA ONLINE

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Description: Trees or shrubs, winter buds with a single, non-sticky outer scale.

Leaves mostly deciduous, mostly linear to elliptic to oblong, margins mostly toothed; petiole less than a quarter as long as lamina.

Floral bracts entire or finely toothed; flowers with 1 or 2 tongue-like glands or rarely a small cup-like gland. Stamens 1–15, filaments free or fused. Ovary mostly 2-carpellate, ovules 4–many, stigma entire or 2-lobed, sessile or on a slender style.

Capsule 2-valved; seeds with silky hairs.

Distribution and occurrence: World: c. 400 spp., mainly temperate & subarctic regions of N. Hemisphere, a few species extending into the tropical & S. Hemisphere. Australia: 12–14 species and several hybrids (some named) naturalised, and many more cultivated.

Most species were introduced into Australia as potential economic plants, for timber, basketry or soil stabilisation, or as ornamentals. As willow seed is very short-lived, all of the early introductions of willows were made as cuttings or pot plants. This meant that most of the plants of any species, or at least the plantings at any one site, were derived from one or very few individuals. As plants are mostly either male or female this has meant that most of the clones were unisexual and plantings rarely produced seed or seedlings. Seed was only possible from hybridisation of two different species where the correct sexes were present, the flowering times overlapped, and the trees were less than 500 m apart (about the maximum effective distance for the pollinating insects). The sparsity of overlap of flowering times for the different species has meant that seeds were rarely formed. Over the years more species and cultivars have been introduced. Some of these cultivars were hybrids between other species, often very rare hybrids. If such hybrids are planted, and either or both parent species are around, they can overcome the problems of non-overlapping flowering times, and also reduce the inter-species fertility barriers. Simply increasing plantings has allowed a greater opportunity for trees to cross pollinate. With both types of increased plantings there is now an opportunity for fertile and viable seed to be formed. Also, as the trees aged, the longer they tended to flower and the more likely that overlaps occurred. Air travel has also meant viable seed could be imported, producing mixed-sex populations of some species. All such situations have occurred and there are now areas where there has been mass colonisation by seedling wilows.

Identification: For positive identification of species, hybrids and cultivars, it may be necessary to collect from the same tree when flowering in spring and in full leaf in summer. The leaves should be collected from branch systems that have borne flowers the current season and not from the vigorous sterile shoots arsing from near the base.

The ridges in key lead 17, are the ridges that are present on the wood underneath the bark (strip bark to see).

Key based on Meikle, R.D. (1984); Carr G.W. (1996); and Cremer, K.W. (1995) and parts of the original treatment in Flora of N.S.W. (1990).