Fungi Key – Earthstars


The Earthstars are members of the Lycoperdaceae, the puffballs, and are in the
genus Geastrum. They have a different structure to other fungi and are even
different from other puffballs, so people who study them use terms that you may be
unfamiliar with. A short glossary and some diagrams are provided below to help.

  • Asperate – with a roughened surface
  • Endoperidium – the inner ‘ball’ that contains the spores
  • Exoperidium – the outer covering that contains the endoperidium and which splits to
  • form the stars or rays as the fungus matures
  • Glabrous – with a smooth surface
  • Hygroscopic – the rays close in dry weather, they become involute
  • Non-hygroscopic – the rays remain in a permanently expanded state
  • Pedicellate – with a stalk between the exoperidium and the ‘ball’
  • Peristome – a complex structure at the top of the ‘ball’ which can be:
    • Sulcate – grooved
    • Fibrillose – surrounded by thin fibres
  • Rays –the individual splits of the exoperidium; they can be:
    • Involute – incurved partially enclosing the endoperidium like a lotus flower
    • Revolute – recurved, bending downwards and lifting it off the ground
  • Rugose – wrinkled
  • Stoma – the pore at the top of the ball where the spores are released. It may be
  • simple (naked) or complex (peristome)
  • Tomentose – felted

Some Geastrums have changed their names. The latest species names are given in
the key; the older names (shown in brackets) are often on Herbarium specimen

Trial Key for Geastrum

1.Stoma naked2
1.Stoma with peristome3
2.Exoperidium hygroscopic, acute rays involuteG. floriforme
2.Exoperidium not hygroscopic, wide rugose rays, endoperidium
pedicellate (G. fenestratum)
G. fornicatum
3.Peristome sulcate4
3.Peristome fibrillose7
4.Exoperidium not hygroscopic, revolute, endoperidium
pedicellate, spores 5.5 – 7.5 µm diameter (G. pectinatum)
G. tenuipes
4.Exoperidium hygroscopic, involute5
5.Endoperidium sessile, involute (G. drummondii)G. ambiguum
5.Endoperidium pedicellate, thick and rugose on outside6
6.Endoperidium asperate, spores 6 – 8 µm diameterG. campestre
6.Endoperidium glabrous, spores 4 – 5.5 µm diameterG. clelandii
7.Stars small, < 30 mm diameter, endoperidium pedicellateG. austrominimum
7.Endoperidium sessile (pedicel absent), stars larger than 30 mm diameter8
8.Exoperidium tomentose (G. velutinum)G. javanicum
8.Exoperidium glabrous9
9.With a collar between the exoperidium and the endoperidium,
spores 4 – 5 µm diameter
G. triplex
9.Lacking a collar, spores either larger or smaller10
10Spores 2.5 – 3.5 µm diameterG. saccatum
10.Spores 7 – 8 µm diameterG. australe

Note: G. triplex is the most common earthstar recorded in Queensland; G. saccatum
is also known from several collections; all the others appear to be rare, with only 1 to
3 collections. If you find an earthstar, photograph it, collect it, make careful notes
using this key and then deposit it at the Queensland Herbarium at Mt Coot-tha.

Gretchen Evans
25 April 2022
Version 1.3