Dicrastylis archeri - Lamiaceae

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Dicrastylis archeri - Lamiaceae

Dicrastylis in WA is now placed into the Lamiaceae family, but depending on the classification being used, may still be listed in Chloanthaceae by some authorities. Plants in this genus are shrubs with a dense covering of cotton/woolly hairs, particularly along their branches; their flowers are mostly five lobed (one larger than the other four) with five stamens, although Dicrastylis archeri differs by having either four or five lobed flowers and commonly only four stamens.

This species, plus Dicrastylis capitellata (see: http://esperancewildflowers.blogspot.com/2011/01/dicrastylis-capitellata-lamiaceae.html), were both only discovered in 1990 NE of Esperance after a bushfire had passed through the area. D. capitellata is more common and occurs in a number of widely scattered compact colonies, although being a smaller plant, is quickly overgrown and disappears within a few years. D. archeri on the other hand is more restricted and only found in three colonies within 10 km (6 miles) of each other and approximately 20 km NNE of Mt Heywood. Apparently, another colony has been more recently discovered around 400 km west of the above colonies in the Lake Grace region, but I know nothing of these plants, except to say there is a considerable amount of poorly known bushland between, so possibly Dicrastylis archeri will also be found there.

Dicrastylis archeri has a Priority One Conservation Status, which means it is known only from less than 5 populations and is urgently in need of further survey. It is a spindly upright plant growing to around 1.2 metres (4’) high in sandy hollows, often in open mallee woodland with scattered Banksia media and a variety of heath plants. As D. archeri is over twice the height of Dicrastylis capitellata, it can survive competition from other shrubs for ten or so years, but by then their numbers are greatly depleted. Their white flowers fade to cream and form terminal floral clusters that are produced during November and December.

Prostanthera serpyllifolia subsp. microphylla - Small-leaf Mint Bush

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Prostanthera serpyllifolia subsp. microphylla - Small-leaf Mint Bush

Prostanthera serpyllifolia has two subspecies, this one and subsp. serpyllifolia, the latter being quite rare in the Esperance region. Subsp. microphylla is more frequently encountered and can be found in a variety of habitats from coastal regions to the inland mallee where more common. Generally it prefers sandy non-calcareous well-drained loams, over heavier loams or clay (in hollows) or overlying limestone (typical of the mallee and Nullarbor).

Prostanthera serpyllifolia subsp. microphylla the Small-leaf Mint Bush is aptly named as the leaves are under 4 mm (3/16”) in length, plus the leaf stalks (petioles) are also very short being less than 0.5 mm. The leaves tend to be clustered in small bunches and spread along the stem, plus the calyx (under the coloured flower) is less than 8 mm in length. With the other subspecies (subsp. serpyllifolia) all the above are larger and the leaves are not clustered along the stem. For more information concerning this subspecies, see http://esperancewildflowers.blogspot.com/2011/03/prostanthera-serpyllifolia-subsp.html

The hairs on the Small-leaf Mint Bush tend to be more numerous, particularly along the branches, but hairiness generally can be quite variable between populations. Due to the small and often spaced leaf clusters, Prostanthera serpyllifolia subsp. microphylla has a more open structure and can appear a little twiggy. It grows to around ½ metre (18”) in height, commonly in compact colonies after fire or soil disturbance.

Flower colour is another variable feature, differing from red to pale pink, but more frequently with a mixture of hues. Due to this species preference for drier environments, it is officially recorded flowering in WA from April to December (occurs north of Albany, then east across the Nullarbor into SA, Victoria and NSW), however this timing can vary considerably as different colonies respond to local weather conditions. Around Esperance, between August and November would be its customarily flowering period.  Flower size is similar to subsp. serpyllifolia of around 2 cm (3/4”) in length.

Prostanthera serpyllifolia subsp. serpyllifolia – Thyme-leaved Mintbush

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Prostanthera serpyllifolia subsp. serpyllifolia – Thyme-leaved Mintbush

Plants in the Prostanthera genus (also known as Mintbushes) are now commonly placed in the Lamiaceae family, but may still be held in Labiatae by some authorities. In Western Australia there are only three widely spaced records of Prostanthera serpyllifolia subsp. serpyllifolia namely Lake Grace, Zanthus and a near coastal collection on the Nullarbor, it is also recorded from South Australia's Eyre Peninsula, but none for the Esperance region. However, the photos above were of a colony growing with Eremophila serpens (see post under that name in lower right column) on Lake Halbert, east of Mt Ridley and 70 km (43 miles) NE of Esperance.

In this unusual Lake Halbert habitat there are a number of plants, but these are very localised and restricted to thin strips of sandy loam, surrounded on all sides by samphire communities growing in a clay/gypsum loam. This is the only location I have seen these plants, but they may also exist in similar habitats on other playa lakes within the region. The other subspecies Prostanthera serpyllifolia subsp. microphylla, the Small-leaf Mintbush is quite common in the northern Esperance Mallee.

The subsp. serpyllifolia differs from subsp. microphylla in several ways, the most obvious being the leaf size, being larger with subsp. serpyllifolia from 4-13 mm (almost 3/16” to over ½”), whilst subsp. microphylla are less than 4 mm in length. The leaves are also flatter and more evenly spaced along the stem; subsp. microphylla leaves are more recurved and clustered along the stem. The petiole (leaf stalk) is longer 0.4-1.5 mm or more with subsp. serpyllifolia, but sessile or to 0.5 mm with subsp. microphylla. Also the calyx with subsp. serpyllifolia is longer 6-12 mm (1/4”-1/2”), but only between 5-7.5 mm with subsp. microphylla.

The Thyme-leaved Mintbush is reasonably bushy and grows to ½ metre (18”) in height, the red flowers (to 2 cm or ¾” in length) were very eye-catching and no doubt attracted visiting honeyeaters who also checked out the Eremophila serpens flowers whilst there. Flowering time is recorded from August to December (Flora of SA), with the above in bloom during October.

Maireana erioclada – Rosy Bluebush

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Maireana erioclada – Rosy Bluebush

The Maireana genus (also known as Bluebushes) is part of Chenopodiaceae, which is a large diverse family containing a substantial number of plants that grow in saline and/or calcareous environments. Such habitats are found around the coast, in saltmarsh, saltlakes, around the edges of salty streams and lakes, or over limestone. Maireana erioclada favours the inland region in well-drained environments, some of the photos above were taken of plants growing on deep gypsum mounds that are exceedingly dry places; they also prefer open habitats so 1-2 years after soil disturbance or a bushfire can have plants making an appearance.

Maireana have small flowers that are surrounded by a horizontal wing/wings and sometimes with appendages above and additional wings below. These are collectively known as a fruiting-perianth as they persist and continue to develop after the flower has finished and the seed has formed. Although the flowers are small and largely insignificant, the wing arrangement is the ornamentation and secondly the fleshy or succulent bluish foliage.

Maireana erioclada grows to around 60 cm (24”) in height and is found in WA from the NE of Albany to Kalgoorlie, then across the Nullarbor to SA, Victoria and outback NSW. This species in this genus is one of the most attractive, with initially spectacular golden yellow perianths that age crimson and can completely obscure the foliage (later to grow through). The shapes of the perianth wings are quite distinctive to each species and a major classification feature; another (for this species) is the appressed white woolly branches, plus the leaves are succulent and club-shaped.  August to October would be the best time to see this colourful species.

Thomasia cognata – Sterculiaceae

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Thomasia cognata – Sterculiaceae

The Thomasia genus is part of the Sterculiaceae family along with other notable genera like Brachychiton, Rulingia, Guichenotia, Lasiopetalum and others. Apart from Brachychiton, which is a tree, all others are shrubs, many with a conspicuous covering of stellate hairs (several hairs radiating star-like from a common centre). The genera are relatively straightforward to distinguish one from the other, but they can be very fiddly when trying to key out the species, due to similar shaped floral and foliage components, although they are obviously different in the field or if specimens of other species are available for comparison.

Thomasia is separated from other genera by (mostly) having small scale like petals (in this instance these are red near the centre of the flower); anthers that open in terminal pores or slits, which face towards the centre of the flower; each calyx lobe has one prominent rib (the calyx lobes look like white or pale pink petals and make up the major portion of the flower); the three bracteoles (green lobes under the calyx) are broad and conspicuous.

Thomasia cognata is very habitat specific, preferring the calcareous sands in stabilised near coastal dunes. Here particularly after bushfire, they can be common in hollows, flats and lower dune slopes. Along the south coast of WA there are few collection records, although in habitat they can be quite common. Probably most plant people do most of their botanising in non-calcareous soils a little inland, where flora diversity is much greater. Currently from very patchy collections, they are noted from Esperance around the coast to north of Perth.

This is a small compact shrub rarely exceeding 30 cm (12”) in height, but commonly spreading 60 cm (24”). Flowers are over 1 cm (1/2”) diameter and bloom (often consistently) from August to November.

Eucalyptus forrestiana - Fuchsia Gum

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Eucalyptus forrestiana - Fuchsia Gum

The Fuchsia Gum, also known as the Fuchsia Mallee, is a popular nursery species and well known to many gardeners, however few realise it only naturally occurs in mallee country to the NW and NE of Esperance, with the Peak Charles region being its most northerly limit. Eucalyptus forrestiana until recently had three subspecies, which have been reclassified into separate species. These are now known as E. dolichorrhyncha, which has a much longer operculum than E. forrestiana and E. stoatei that has additional ribs around the fruit. The latter has been documented here (see lower right-hand column).

Eucalyptus forrestiana is quite variable in height, from 2-8 metres (6’- 26’) in height, the shorter ones often mallee like (multiple stems) growing in shallow sandy soils over limestone, whilst the larger tree like ones (single trunk) favour low-lying areas in deeper heavier loams. They are also found in sandy/clay soils over broken granite. The trunks are silvery grey with pinkish highlights and uncluttered with old dead stems.

Initially buds are greenish, changing to yellow/red and commonly progressing to bright glossy red. The fruits remain red for several months, but gradually change to brown, purple and grey. The actual flowers are yellow and relatively small, playing a secondary ornamental role to the hanging red capsules, which are strongly four ribbed and grow to around 5 cm (2”) long and 3 cm (over 1”) wide.  The stalk is another 5 cm in length, so are very noticeable.

With such spectacular fruits, flowering times are less important regarding visual appeal, but they can bloom throughout summer and autumn, although the main period may vary depending on environmental and weather conditions. Where Eucalyptus forrestiana occur, they are often very common and demand your attention as you pass through.

Lobelia anceps – Angled Lobelia

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Typical plants growing in a non-calcareous sandy/peat soil

Plants growing in deep calcareous sand near creek outlet to the sea

Plants from a hollow and seepage zone in deep calcareous sand

Lobelia anceps – Angled Lobelia

In Western Australia due to the Classification System now adopted, Lobelia anceps is regarded as belonging to the Campanulaceae family, but may be placed into Lobeliaceae elsewhere. The species name has also been known as Lobelia alata, but has now been universally changed to Lobelia anceps. This species is very widespread and in Australia occurs from Geraldton (north of Perth) around the south coast (including, SA, Victoria, Tasmania and NSW) to north of Brisbane in Queensland, where commonly found in near coastal, cool moist soils. It is also found in New Zealand, South America and South Africa.

Lobelia anceps is a low sparsely branched perennial that will ramble near the ground or lean against taller vegetation to a height of around a metre (3’). It will grow in sun or shade, but requires a moist soil in exposed situations, so is usually encountered around seepage areas, swamps, lakes, streams, etc. It mainly flowers in the warmer months (September to May), but blossom can be found anytime.

Most Lobelia spp. are very sensitive to soil type, particularly the pH by either growing in acid or alkaline conditions. Locally, Lobelia anceps grows in both soils, but when in calcareous soil has different features from the norm and is probably evolving into a different species, but to what extent it has progressed down this path and if it should be classified differently, requires further study.

The above photographs have been divided into three groups, with the top four taken from plants growing around a non-calcareous sandy/peat soil and are reasonable typical of this species.

The centre four photos are from plants that were growing in an exposed moist situation, in deep calcareous sand near a creek outlet to the sea.

The bottom four photos are from plants growing around a hollow and seepage zone in deep calcareous sand, also close to the sea, but a more sheltered position.

The three colonies above are within 14 km (8.5 miles) of each other, to the west, and south of Mt. Merivale (20 km east of Esperance).