Calothamnus gibbosus – Corky Net-bush

Click image to enlarge

Calothamnus gibbosus – Corky Net-bush

Shrubs in the Calothamnus genus are commonly known as One-sided Bottlebrushes or Net-bushes and belong to the exceptionally large and diverse Myrtaceae family. Calothamnus gibbosus occurs NW of Esperance (mostly west of Lort River, 65 km or 40 miles away) to the Stirling Range (NE of Albany), growing on sandy clay loams, sometimes over gravel and generally 10-60 km (6-40 miles) from the coast. This favoured location often places this plant in conflict with farming land, resulting in many colonies restricted to roadside reserves. However it is still reasonably common and can be found in sizeable compact colonies, although these tend to be localised.

Calothamnus gibbosus has been confused with Calothamnus gracilis, which is a very common and widespread species often overlapping with C. gibbosus, although they are rarely found growing together. The general appearance of young plants is very similar, but as they mature the leaves of C. gibbosus become noticeably shorter and thicker, plus more prickly. However it is the stems that differ the most, with this species producing swollen growths along the stems that eventually produce the red flowers, of which the calyx (cup at flower base, but not the petals) are total immersed. The calyx of Calothamnus gracilis is at most only partially immersed.

The fruits remain partially buried in the corky stems and are without ornamentation, whereas C. gracilis are usually ribbed or have nodule ornamentation. The stems of mature plants become more of a feature as they produce a thick corky structure, whereas Calothamnus gracilis as its name suggests has a more slender/graceful appearance. Calothamnus gibbosus tends to grow with heath species, under small mallee eucalypts where recorded growing to 1.5 metres (5’), but are mostly less than 1 metre (3’) in height. The bird attracting flowers are produced between May and November, with the exact timing determined by local weather conditions.

Calothamnus tuberosus - Myrtaceae

Click image to enlarge

Calothamnus tuberosus - Myrtaceae

Common to the larger and more sparsely vegetated inland granite outcrops to the north and NE of Esperance. It is a dry country shrub favouring the mallee region with an average annual rainfall of between 200 mm to 500 mm (8" to less than 20"), which in periods of drought can be considerably less. Calothamnus tuberosus is a spreading shrub growing to 4 metres (over 12') in height, although half this size is more the norm. For such a large plant to thrive on these exposed dry rocky outcrops in shallow soils, with roots having to take advantage of every fault, crack and crevice requires special attributes for survival. This it does by having a lignotuber and tuberous roots that store food and moisture for use during hard times.

Interestingly, the distribution of Calothamnus tuberosus overlaps in the southern (higher rainfall) districts with another granite clinging shrub, Hakea clavata that is more common in coastal regions http://esperancewildflowers.blogspot.com/2009/02/coastal-hakea-hakea-clavata.html. Although this Hakea might need a slightly higher rainfall, it is still in a very harsh environment by the bare rock exposure and often completely dry conditions throughout summer. This plant handles these survival problems by producing thick fleshy and moisture retaining leaves to help it overcome the prolonged dry/hot periods.

At first glance, Calothamnus tuberosus looks like a giant version of another one-sided-bottlebrush, Calothamnus gracilis as they both have grey/green upright and rounded (terete) foliage, but on closer inspection they are very different from each other. The leaves of Calothamnus tuberosus are thick and rigid with a very stiff sharp point. These leaves will not give way when brushed against and can easily penetrate skin, so there is a need to approach with care.

The flowers like most Calothamnus species are a rich red and occur in long or short spikes along old growth branches (the length of the spike probably relating to recent weather conditions and the limitations of the habitat). Also they have a long flowering period and providing weather conditions are not extreme, blossom can usually be found somewhere on the outcrop, although November to January tend to be best for widespread flowering.

Honeyeaters are the main pollinators and it is worth mentioning how the flowers are positioned on the shrub. The long sharply pointed foliage would effortlessly skewer the birds should they try to land on top and bend down into the flowers, but flowers form near the leaf base, so birds fly to the flowers side-on and below the foliage tops, to then feed and pollinate between the vertical leaves. However the sharp foliage can still fend off grazing animals that would otherwise readily consume them if they were unarmed.

 
Update January 2011
Two photos added.

Calothamnus gracilis - Myrtaceae

Click image to enlarge

Calothamnus gracilis - Myrtaceae

This Calothamnus species is usually less than a metre (3') in height, although it can grow to around 1.5 metres (5'). It is very common and widespread with a preference for sand and/or gravel soils in heathland environments, where it will grow from low-lying habitats (not swampy) to the tops of deep sand hills.

The upright foliage is not particularly prickly and as branches are usually brushed aside when walking past, the pointed leaves are seldom encountered. Even when they are, being long and slender they easily give-way, so skin penetration seldom happens. The dark red flowers attract honeyeating birds and provide nectar over long periods, which with good rainfall can be year round. This species is quite strange in the way it flowers, I have seen odd shrubs in full bloom, whilst neighbouring ones are not even setting buds. Others will flower off and on throughout the year and some have only a single grand fling. Moisture availability obviously plays a part in this, which is illustrated when during long dry summers, blossom is rarely produced.

Calothamnus gracilis is quite distinctive in size, foliage and habitat preference, but to confirm identity, the flower parts (petals, stamens and calyx-lobes) are in sets of five, plus the calyx base is embedded into the branch.

Woolly Net-bush - Calothamnus villosus

Click image to enlarge

Woolly Net-bush - Calothamnus villosus

Calothamnus villosus, also known as the Silky Net-bush is a shrub to 2 metres (over 6') in height and tending to grow in thickets on sand or gravel, particularly over granite. Although common where found, it is not widespread in the Esperance region and to my knowledge is only found in the Cape Le Grand National Park and on the mid to lower slopes of Mt. Burdett 50 km or 30 miles NE of Esperance, plus nearby along Wittenoon Road.

Easily separated from Calothamnus quadrifidus by the number of floral parts (calyx, petals and stamen bundles), which are in sets of five, whereas C. quadrifidus are in sets of four, also the seed capsules are shaped differently, but once both shrubs have been seen, they are quite distinct even from a distance. The blood red flowers are around 3 cm (over 1") in length and are very good for attracting honeyeating birds. Like most Net-bushes, the Woolly Net-bush can flower for considerable periods and odd flowers can usually be found year round, although winter/spring is their main period.

One-sided Bottlebrush - Calothamnus quadrifidus subsp. quadrifidus

Click image to enlarge

One-sided Bottlebrush - Calothamnus quadrifidus subsp. quadrifidus

An extremely hardy and widespread shrub to 3 metres (10') in height, although more commonly closer to 2 metres (6'6") or even less. I have encountered this species from within metres of the coast to high inland granite outcrops. Also I have seen it growing in acid or slightly alkaline sandy soil, particularly when over clay, gravel, limestone or rock. However there is one place where they are nearly always found, which is in rocky gullies on granite outcrops where they can form dense impenetrable thickets, although you can often crawl into them on hands and knees. In this cool sheltered environment where the soil has been enriched by the slow decomposition of their leaves, numerous orchids, fungi, lichens and mosses are to be found, along with the scratchings of local indigenous mammals.

With such a widespread plant and a liking for so many habitat types, there are numerous forms that sometimes make positive identification difficult, especially if too much attention is placed on the foliage. The leaves can be long or short, deep green to yellowish, hairy or not, flat and broad or thin and round, plus with or without bumps. To help identify, the stamen bundles of the flowers will number only 4 and will be of equal width, length and general appearance, not 5 and/or unequal as with most other species. The top of the seed capsules are reasonably distinctive too.

The One-sided Bottlebrush has small petals, but large bright red stamen bundles that make a striking display over many months. The honeyeating birds are greatly attracted to this shrub and are constantly moving from flower to flower, whilst small insectivorous species scramble through the thickets in search of invertebrates. Flowering can span from June to December, but with good rainfall it can bloom even longer.


Update: December 2010
In the Nuytsia publication of the WA Herbarium Vol. 20, the species Calothamnus quadrifidus has been divided into a number of subspecies, but only subsp. quadrifidus is listed for the Esperance region. This subspecies is by far the most common and widespread, by occurring from Israelite Bay (east of Esperance) to south of Geraldton. It is separated from other subspecies by having all or most leaves less than 3.5 cm (1 3/8”) in length; they are also terete or semicircular in cross section, plus usually hairy. I might add that locally it is still a highly variable shrub, although falling into the above specification.