Guides’ plant of the month for October

The scented sun orchid (Thelymitra macrophylla) is a beautiful orchid which occurs in limited locations in the Kings Park bushland, flowering mainly in late September to early November.

Flowers are mostly blue but can be mauve or even pink.

Thelymitras are known as sun orchids because the flowers only open fully in sun, remaining closed during the night and in cloudy conditions.

The genus name is derived from the Greek words thely (female) and mitra (mitre hat), referring to the appearance of the hooded column (the orchid’s reproductive structure). A distinguishing characteristic of the species is its big leaves, hence the name macrophylla.

The flowers are carried on an elongated inflorescence of about 10–20 individual flowers.

In most orchids the lower petal is modified into the labellum or lip, which bears the rostellum or beak which contains the modified stigma and stamens. However, in the Thelymitra genus, all six petals and sepals look similar with no obvious lip.

As the common name indicates, the scented sun orchid is often sweetly scented but like many orchids it has no nectar and offers no reward to its pollinator, a native bee. To attract the bee, its blue colour mimics that of other blue flowers in the vicinity.

The seeds are very tiny and numerous, like dust. Orchid seeds lack food reserves so depend on an orchid mycorrhizal fungus to provide the nutrients necessary for germination and growth of the new plant.

To find the scented sun orchid or other Thelymitras such as the leopard orchid (Thelymitra fuscolutea) or the blue lady orchid (Thelymitra crinita) you will need to search on sunny days. Check with the Visitor Information Centre for likely locations or join one of our seasonal walks this month.