For botanists racing to save critically endangered species, it’s a challenge

In Australia we have about 1550 orchid species, almost all of them found nowhere else. Can these precious plants be saved?

Delightful: Queen of Sheba orchid

Orchidaceae is the second largest family of flowering plants, containing an estimated 30,000 species of orchids from more than 800 genera. If you add in cultivars and hybrids, you’re looking at possibly 100,000 different kinds.

In Australia, we have about 1550 orchid species, almost all of them found nowhere else. About 80 per cent of them grow in the ground (called terrestrial orchids) and are inconspicuous unless in flower. The rest grow on trees and rocks (as do most of the world’s orchids), the best known of these being the Sydney rock orchid (Dendrobium speciosum) and Cooktown orchid (Dendrobium bigibbum).

Our terrestrial orchids are mostly found in grasslands, heathlands and sparser forests; owing to agricultural and suburban expansion, rabbits, weeds and drought, many are endangered. Typically, they die down to a dormant tuber in summer when it’s dry, then grow rapidly as rains arrive in autumn and winter, to bloom in spring. Most are small and delicate-looking with exquisitely beautiful flowers. Not only are they adapted to bushfires, many will flower more profusely after a burn – and some even require it.

Pouched leek orchid

There are about 400 terrestrial species concentrated in the biodiversity hotspot of southern WA, where orchid spotting is an exciting part of experiencing the spectacular wildflower displays in spring. The orchids’ common names often reflect their flower shape, such as duck, spider, bunny, hare, mosquito, donkey and bird orchids. There are pink and purple enamel orchids (Elythranthera) whose petals shine like glossy enamel, and bizarre-looking hammer orchids (Drakaea). Sun orchids (Thelymitra) usually open their pretty flowers only on warm, sunny days; most spectacular is the multicoloured Queen of Sheba (T. speciosa).

Rhizanthella. Picture: Noel Hoffman

One of our strangest is the underground orchid, Rhizanthella, which has three NSW species and two in WA, all endangered. They spend their life cycle underground, the tubers producing flowers just under the leaf litter in spring. The flower structure is about the size of a 50c piece; the berry-like fruit is unusual for an orchid and smells like vanilla (which also comes from an orchid, but from the tropics).

All orchids rely on specialised mycorrhizal fungi, which live in the roots and soil, to help their seeds germinate and the seedlings to grow. This symbiotic relationship is very strong in terrestrial orchids, making them especially difficult to cultivate. For botanists racing to save critically endangered species through propagation/reintroduction programs, it’s a challenge.

Q&A

A neighbour gave us a climbing spinach plant with red stems that now has clusters of black berries. Are they seeds? Barbara Jones, Mareeba, Qld

Malabar spinach (Basella rubra with red stems and B. alba with green stems) produces juicy black-purple berries that are edible raw or cooked, and full of antioxidants. The pips inside the berries are the seeds, which germinate easily.

We have a mass of self-sown dragon trees at the base of our fairly mature specimen. Can we dig them out to transplant? Craig Ellis, Perth

Yes, do it now before it gets hot and while they’re still small. Pot them into a propagating or succulent potting mix. Dracaena draco grows only about 25cm per year. Once the initial single stem flowers after 10 to 30 years, it starts to branch. As the new branches flower, after a decade or two, they too branch; ultimately it becomes a sculptural umbrella shape. Plants can live to 400 years.

The crotons I planted for colour a few months ago all look sick and lost their leaves. Why?

Michael Arnold, Sydney

Crotons are tropical plants that rarely survive Sydney winters unless in a warm microclimate. In future, you could keep them in pots in the garden and move them indoors for winter.

The Gardening prize

Send your questions to: [e-mail] or PO Box 3098, Willoughby North, NSW 2068. The best question for September wins a year’s subscription to ABC Gardening Australia and ABC Organic Gardener magazines, worth $109. August’s winner is Natalie Moloney of Brisbane for her question about feijoas