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.

Dicrastylis capitellata – Lamiaceae

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Dicrastylis capitellata – Lamiaceae

There are a number of Dicrastylis species, but they are not well known possibly because most tend to grow in remote, out of the way places that are often hot and dry in summer, therefore seldom visited. Due to these isolating conditions, a number have only been discovered within the past 20 years, including this one. First discovered in sandy areas within mallee country 30-50 km (20-30 miles) to the North and NE of Mt Heywood, it a shrub to ½ metre (18”) in height and only occurs after bushfires to form localised but sizable colonies. These slowly die off over a few years, as developing larger vegetation begins to dominate light and moisture availability.

Mt Heywood is 85 km (50 miles) NE of Esperance and the region further north, where Dicrastylis capitellata grows is very poorly known. To illustrate that, you can go from there north to Broom (1700 km 1060 miles) and not encounter a single settlement, you will also only cross two bitumen roads. Most of this country however is desert and very difficult to access. Returning to Dicrastylis capitellata, I know it from several colonies in an area 20x30 km (12x18 miles), but apprantly it has since been found near Mt Holland, which is 190 km (120 miles) west of Norseman and about 300 km (185 miles) from the Mt Heywood colonies. So likely this species occurs in suitable habitat in the also poorly known country between.

Currently Dicrastylis capitellata has a Priority One Conservation Status, which means it is poorly known from less than 5 populations and due to its small population size is under threat. Personally I know it from more than 5 sizable colonies, which does not include the Mt Holland ones. However the problem with official records is those doing the recording must be at the site 2-4 years after a bushfire as no plants will be seen if visited at other times, .

In habitat, Dicrastylis capitellata favours sandy loam flats in low-lying areas over limestone, these regions normally support eucalyptus and Melaleuca species, which after bushfires leave only a narrow window for these plants to reproduce before they are crowded out. The pink/blue flowers form into small heads, which progressively come into bloom, moving from the base to the branch tips. These branches are unusual in that the portion with the flowering heads, bend outward almost 90 degrees, so all flowers form a near horizontal flat plain to provide unhindered access to pollinators.

The Herbarium website records Dicrastylis capitellata flowering in May, which I think is an error, or refers to the Mt Holland colonies, but those to the north of Mt Heywood are known to flower November to January. Some variation to this period may happen with unseasonal rainfall, but due to their robust flowering stems, I doubt if they could grow these quickly enough much outside these times, before the regions summer temperatures (commonly 35-40 degrees C or 100 degrees F) cause rainfall to evaporate.