Salix viminalis L.

Multi-stemmed shrub. Branchlet wood without ridges or with sparse, short ridges 2–6 mm long. Current year's branchlets densely tomentose, the hairs not persistent, yellow to orange-yellow (UCL87–71). Flower buds 5.0 mm long, 1.8 mm wide, 1.3 mm deep, narrowly ovoid, 2-keeled, pubescent. Leaf buds hairy, densely short-silky. Leaves alternate, not falcate. Stipule 0.5–9 mm long, 0.7–3.0 mm wide, very narrowly ovate to linear, deciduous. Petiole 2.5–7 mm long, densely tomentose, groove present or absent, glands absent, base not expanded, pale yellow to yellow-green. Emerging leaves green, with moderately densely short-silky hairs. Proximal leaves entire. Leaf lamina 70–175 mm long, 5–20 mm wide, length to width ratio 6–15:1, very narrowly ovate to very narrowly elliptical; base rounded; apex very narrowly acute; leaf galls absent; margins crenate, slightly undulating, finely revolute to plane; upper lamina surface slightly bullate due to impressed veins, slightly to medium glossy, moderately densely tomentose or glabrous except for tomentum on the midvein, stomata absent; lower lamina surface midvein and usually side-veins raised, not glaucous to distinctly glaucous, densely short- to long-silky hairy. Catkin opening precocious to coetaneous with leaves, catkin flowers opening sequentially from base. Flowering branch 17–25 mm long, with 2 subtending leaves. Male catkin 23–24 mm long, 13 mm diameter; catkin rachis not visible between flowers. Female catkin 13–40 mm long, 6–11 mm diameter; catkin rachis not visible between flowers. Flower bract 2.0–2.7 mm long, 0.5–0.7 mm wide, black at the apex, otherwise green, flat; apex acute, densely long-silky hairy on both surfaces and margins. Male nectaries 1 or 2, inner nectary 0.6–0.7 mm long, 0.20–0.23 mm wide, green. Stamens 2, filaments free, glabrous; anthers 0.8–1.3 mm long, yellow, sometimes red-tinted. Female nectary 1, 0.6 mm long, 0.3 mm wide, yellow; ovary 2.2–2.6 mm long, densely short-silky hairy, equal to bract in length but style extending beyond the bract; stipe 0.8 mm long, style base 0.6 mm, style arms 0.9–1.4 mm long, sometimes unequal in length, unlobed to lobed to the style arm base, pale yellow-green.

Leaves are very narrowly elliptical or very narrowly ovate, 70–175 mm long, 5–20 mm wide, with margins crenate. The petiole is short (2–7 mm long). Leaves are persistently silky-hairy below. Female flowers have the ovary densely short-silky hairy, the style arms exceptionally long (0.9–1.4 mm) and unlobed to completely bilobed (all variation between these extremes occurs). The flower bract is ovate, black in the upper half, densely long-silky hairy, and equal in length to the ovary. Male flowers have two stamens and anthers are slightly red-tinted before opening. Skvortsov (1999) stated that the wood lacks ridges, but New Zealand specimens have very sparse, short ridges.

Salix viminalis is most similar to hybrids where S. viminalis is one of the parents, particularly hybrids with the presumed parentage S. caprea × S. cinerea × S. viminalis, formerly known as S. ×dasyclados. Skvortsov (1999, pp. 59–60) found that S. viminalis and S. ×dasyclados overlapped in features so much it was not possible to provide a key.

Another such hybrid present in New Zealand is Salix ×smithiana (S. caprea × S. viminalis), which has a wider leaf lamina (21–23 mm wide, rather than 6–20 mm wide in S. viminalis), branches that are somewhat brittle at their base, and petioles that are flat to convex adaxially.

Salix eleagnos is similar but leaves are smaller (2.6–4.5 mm wide versus 6–12 mm wide in S. viminalis), and the hairs on the underside of the leaves form a fuzzy tomentum (i.e. they are not appressed) while in S. viminalis they are appressed long-silky hairs.

Salix udensis and S. schwerinii are also similar to S. viminalis in leaf size and shape. Salix udensis has wider leaves than S. viminalis (26–30 mm wide in S. udensis versus 6–20 mm wide in S. viminalis) and has sparser short-silky hairs so that the lower leaf surface is visible between the hairs. Salix schwerinii has persistent stipules, while in S. viminalis they are deciduous.

First collection: CHR 115427, C.E. Foweraker, 28 March 1932, "Waimak Road, Christchurch."

First publication: Mistral (2015) noted that S. viminalis was being sold in Christchurch in 1870. This willow, along with Salix purpurea and S. triandra, was grown commercially in New Zealand for basket-making. Allan (1940)​​​​​​​said, "Occasionally escapes from cultivation".

Flowering: Mid-August–early October.

Diploid, 2n = 38 (Argus 2010, CCDB based on 20 counts), provisionally confirmed by flow cytometry using PN312 and PN220 (labelled 'Gigantea'). However, two other clones, PN669 (Salix 'Aquatica Gigantea Korso') and PN245, are tetraploid and may be hybrids.