Marsh (Banksia paludosa)

Description

The two subspecies of Banksia paludosa are identical in foliage and flower, and differ only on their size, habit, and response to bushfire. Banksia paludosa subspecies paludosa is most commonly encountered as a spreading multistemmed shrub generally under 1.5 m (5 ft) high, or rarely 2 m (7 ft). In heathland habitats such as Nadgee or Barren Grounds Nature Reserves, it may not exceed 1 m (3 ft) in height. At an exposed area such as Green Cape, it is reduced further to a 30 cm (12 in) prostrate shrub. This subspecies has a woody base, known as a lignotuber, which begins developing in the first year of life. Banksia paludosa subspecies astrolux is a more open non-lignotuberous shrub which reaches 5 m (16 ft) high. The bark and foliage is rough and covered in multiplication signs, although the new growth is covered in fine hair. The stems are generally less than 2 cm (0.8 in) in diameter, and may be red or yellow when young. The leaves are alternate or whorled along the stems, and spear- to egg-shaped (lanceolate to obovate) in shape. They measure 4–13 cm (1.6–5.2 in) long and 1–3 cm (0.4–1.2 in) wide. The leaf margins are entire or have occasional serrations. The leaf undersurface is white, with a midrib.Flowering occurs over autumn and winter (April to July) and the flower spikes, known as inflorescences, arise from stems that are three or more years old. Cylindrical in shape, they are composed of a central woody spike or axis from which a large number of compact floral units arise perpendicularly to it, and are generally 3.2–4 cm (1.3–1.8 in) wide and 7–13 cm (2.8–5.2 in) high. The individual flowers are more openly spaced than those of other banksias, and this is especially evident in late bud.This, coupled with the tall thin shape of the flower spike, makes the species quite distinctive.The flower spikes are pale- to golden brown in bud, and open to a more gold colour after anthesis. Variations are seen, one form having a grey limb in bud, and plants with particularly tall flower spikes have been recorded near Huskisson at Jervis Bay. As with most banksias, in anthesis the opening of the individual buds proceeds up the flower spike from the base to the top (acropetal). The process from bud to the finishing of flowering takes six to eight weeks. As they age, the flower spikes fade to grey, with the old flowers remaining for years. Up to 60 woody follicles develop on each spike, known in this stage as an infructescence. Narrow and elliptic, they measure 0.9–1.8 cm (0.4–0.7 in) long, 0.1–0.5 cm (0.0–0.2 in) high, and 0.3–0.7 cm (0.1–0.3 in) wide. Some follicles open spontaneously, but most remain closed until burnt by bushfire. Each follicle contains one or two fertile seeds, between which lies a woody dark brown separator of similar shape to the seeds. Measuring 1.3–1.8 cm (0.5–0.7 in) in length, the seed is obovate, and composed of a dark brown 0.8–1.3 cm (0.3–0.5 in) wide membranous "wing" and sickle-shaped (falcate) seed proper which measures 0.8–0.9 cm (0.3–0.4 in) long by 0.3–0.4 cm (0.1–0.2 in) wide. The seed surface can be smooth or covered in tiny ridges, and often glistens. The resulting seedling first grows two asymmetrical obovate cotyledon leaves measuring 0.9 cm (0.4 in) long by 0.7 cm (0.3 in) wide, which may remain for several months as several more leaves appear. The first pairs of leaves are oppositely arranged on the stem, have 3–4 "teeth" on their margins, and are narrowly obovate in shape. They are around 1.2–1.4 cm (0.5–0.6 in), and each following pair of leaves is slightly larger.The cotyledons of Banksia paludosa, B. marginata and B. integrifolia are very similar in appearance.The foliages of larger shrubs of both Banksia paludosa subspecies resemble those of Banksia conferta subsp. penicillata, but the latter has a wider inflorescence, and the buds are more crowded in appearance on the inflorescence before anthesis. Banksia paludosa also bears a superficial resemblance to B. oblongifolia, but the latter has a prominent midrib on the leaf underside, the new growth is covered in rusty fur, and the old spikes are bare of flowers. The latter grows on dryer rocky soils while the former grows in wetter sandy soils.