|Microtis media, Illustration.|
The tiny flowers are green and arranged in a many-flowered (50 to 100) spiral in a spike or raceme around the erect and tall central stalk. The lowermost flowers are close the exit of the stalk from the sheathing leaf. The dorsal sepal is sharp-pointed and forms a hood over the column. The lateral sepals are oblong and sometimes recurved. The dorsal sepal often keeps the oblong petals out of sight. The lip is ovate-oblong with united basal calli. The lobed lip has a rough, irregular margin.
Every flower tends to set seed, after being pollinated by wingless worker ants from the genus Iridomyrmex, attracted by nectar at the base of the lip. This is an exceptional case of pollination by ants, since ants tend to secrete an anti-fungal substance that kills pollen. This doesn't seem to affect Microtis pollen.
Microtis orchids are often cryptic and difficult to differentiate. Microtis unifolia seems to have three different groups in New Zealand with different geographical ranges, habitats and flowering times.
Species and subspecies accepted as of June 2014:
- Microtis alba R.Br. (1810) (SW Australia)
- Microtis alboviridis R.J.Bates, (2008) (SW Australia)
- Microtis angusii D.L.Jones (1996) (New South Wales) (endangered)
- Microtis arenaria Lindl. (1840) : Notched Onion Orchid (Victoria, Tasmania)
- Microtis atrata Lindl. (1840) (SW Australia, Tasmania)
- Microtis brownii Rchb.f. (1871) (SW Australia)
- Microtis cupularis (D.L.Jones & G.Brockman) A.P.Br., (2007)(SW Australia)
- Microtis densiflora (Benth.) M.A.Clem. (1989) (SW Australia)
- Microtis eremaea R.J.Bates (1996) (SW Australia)
- Microtis familiaris R.J.Bates (1990) (SW Australia)
- Microtis globula R.J.Bates (1984) (SW Australia)
- Microtis graniticola R.J.Bates, (1996) (SW Australia)
- Microtis media R.Br. (1810) (SW Australia)
- Microtis oblonga R.S.Rogers (1923) (SE Australia)
- Microtis oligantha L.B.Moore, (1968) (New Zealand North Island)
- Microtis orbicularis R.S.Rogers (1907) (S. Australia)
- Microtis parviflora R.Br. (1810) : Slender Onion Orchid syn of M. unifolia
- Microtis pulchella R.Br. (1810) (SW Australia)
- Microtis rara R.Br., Prodr. (1810) (Queensland, New South Wales)
- Microtis unifolia (G.Forst.) Rchb.f. (1871) : Common Onion Orchid (widespread from China, Japan, Philippines, Indonesia, Australia, New Zealand, Melanesia, etc) (abundant)
Most Microtis are very easy to grow, and readily volunteer themselves in other pots. Microtis are often found in gardens around Melbourne from wind-born seed.
- Jones D.L. (1996). "Microtis angusii, a new species of Orchidaceae from Australia". The Orchadian 12 (1): 10–12.
- R. Peakall, A. J. Beattie (1989). "Pollination of the Orchid Microtis parviflora R. Br. by Flightless Worker Ants". Functional Ecology (British Ecological Society) 3 (5): 515–522. doi:10.2307/2389565. JSTOR 2389565.