Endemic to Mexico, Arisaema macrospathum is the only Arisaema from the North American continent found South of the USA border. It is a small species, reaching only around 50cm in height, and in my opinion is an oddly named species, for the spathe does not seem exceptionally large. However, Arisaema macrospathum is a very beautiful plant which can be found in a number of attractive forms.
Spathe colouration can be variable, mostly with shades of green, occasionally with reddish brown reticulations or pale stripes. G. and L. Gusman show a stunning pale green form in their monograph ‘The Genus Arisaema’. Variation can also be seen in the length and colour of the spadix and the colours of the petioles and peduncle. It has only a very short pseudostem of a few centimeters.
Found only in moist and moderately cool temperate cloud forest in mountainous regions of Northern Mexico, this is sadly not hardy in the UK. The forms of Arisaema macrospathum below were originally collected at around 1800m in moist, shaded Quercus germana woodland.
The tuber seems relatively small, reaching around 3 or 4 in diameter. Sessile offsets or bulblets are produced from the tuber.
Seeds and germination:
I have yet to set seed from my plants. However, in common with other members of Section Tortuosa, I expect that seeds cab be stored dry with no significant loss of viability.