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Dianella congesta

Flax Lily / Beach Flax Lily

Family: Asphodelaceae (subfamily Hemerocallidoideae)

Dianella congesta is a clumping lily-herb with rhizomes to 20 cm long, forming mats, usually with inflorescences within the foliage, rising to about 1 metre tall.

It has a mainly coastal-fringe occurrence, growing as far south as Potato Point on the south coast of NSW, north into Queensland, as far north as around mainly Bundaberg but with a few disjunct records near Cairns and Cape York.

It grows in dry sclerophyll woodland and shrubland on coastal sand dunes.

Dianella spp. produce their leaves on a buried condensed rhizome, with some species exhibiting aerial stems with alternate to clustered leaves.
In this species, the leaves are arranged alternately on opposite sides of aerial stems, appearing clustered, to 45 cm long, and to 2 cm wide, mid-green to lighter green. The bases of leaves are occluded – a feature where the two halves of the upper side of every leaf are folded lengthwise and seemingly glued together – a useful identification feature for this species combined with habitat (especially when it is not in flower).

Dianella spp. produce flowers on elevated inflorescences, usually above the foliage, which are described as cymose but have a panicle-like appearance. The individual flowers are blue to violet and are arranged in branches on the main axis. Flowers are bisexual with six tepals (three sepals and three petals which are almost identical – a typical lily-characteristic) and a superior ovary.
In this species, the inflorescence does not really exceed the height of the foliage, with flowers mid- to dark blue, about 15 mm across, occurring in spring–summer. The stamens have yellow filaments and yellow-brown anthers.

Dianella spp. produce berries, usually purple in colour.

Fruit is fleshy, blue to purple, to 12 mm in diameter.

In the garden

This species is restricted in the wild to coastal habitats where, because of its matting characteristics, it is a very effective sand-binder. However, it grows readily in cultivation and has been planted extensively. It is very useful in places such as road-roundabouts and street gardens and similar council landscapes.

Reports have been made that it can spread into bushland areas where it does not naturally belong.

It is hardy in sandy soils. It may tolerate heavier soils but must have adequate drainage.

Can be planted around rocks. A worthy plant for the garden especially planted in odd numbered clumps.

It is a great gap filler and can provide some dense cover for small reptiles and invertebrates.

Most plants in this genus are fast growing and hardy once establish in well-drained soils in a sunny or semi shaded position.

After flowering and after the berries are finished, remove flower spikes at the base of the plant and at the same time remove any dead or yellowing leaves.

Use a suitable native fertiliser for better flower displays.

Propagation

Propagation can be from the ripe seed sown in spring with good success.

Other information

A benefit of Dianella, along with many other monocotyledonous plants, is they can be transplanted. This is best done in Autumn and Winter. Plants can be dug up and divided along the rhizomes and replanted. It is best to cut back the foliage by two-thirds if doing this and replant, where desired, quickly. The author has found this is the quickest way to establish a sizeable plant. Keep transplanted plants moist for a few weeks.

Dianella is a genus of about forty species of monocotyledonous flowering plants (which have been subject to family reclassifications in recent times). They are commonly known as Flax Lillies and are closely related to other native genera such as Thelionema and Herpolirion, as well as, more broadly to Xanthorrhoea and Lomandra.

The genus has much variation and there are likely more species which require formal descriptions.

To view the list of Dianella species accepted by the World Checklist of Selected Plant Families as at October 2020, use this link.
https://en.wikipedia.org/wiki/Dianella_(plant)

Fruit can be eaten raw or cooked and have a comparatively better taste than other species (Wild Food Plants of Australia, Author: Tim Low 1989).

Most Dianella plants will survive fire; regenerating quickly from rhizomes as well as any seedbank.

Dianella – Latin diminutive of Diana – the Roman Goddess of the hunt and wild animals, often associated with woodlands. The first specimen of this genus was collected from the island of Mauritius by French botanist-explorer Philibert Commerson (1727-1773) and was simply labelled “Diana”.
congesta – from Latin meaning “congested” or “crowded together”, referring to the crowded nature of the foliage.

Not considered to be at risk of extinction in the wild.

Plants of South-Eastern New South Wales – Dianella congesta profile page
https://apps.lucidcentral.org/plants_se_nsw/text/entities/dianella_congesta.htm

NSW Flora Online (PlantNET) – Dianella congesta profile page
https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Dianella~congesta

By Jeff Howes, edited Dan Clarke