The genusArisaema 

 Number of taxa 

There is some doubt as to the actual number of species of Ariasaema.

The following table gives some values found online from various sources.

The International Aroid Society, (IAS), gives a list of 498 species, varieties and forms _[11] and a list of 31 cultivars. _[12]

There is also some uncertainty as to which species are hardy. IAS has published lists of 44_[13] & 63_[14] species it considers to be hardy. Arisaema Information has a list of 46 species it classifies as hardy and one of 31 species it feels need to be overwintered in a frost-free enviroment._[8]

However, the latter list from 'Arisaema Information' contains A. speciosum which we've have grown outside for a number of years and which has survived winter lows of -10ºC, although it has never flowered.

I think that the IAS figures are likely to be the most reliable.

The list of 63 hardy species contains nine which require an American Plant Zone value of 7b, (-12ºC to -15ºC), or warmer. Lower temperatures than these are reached at Redhall about once every five years so our definition of hardiness has to end at 7a. There are also a number of synonyms and varieties in this list so, when these are removed, I'm taking the remaining 43 plants from the IAS list as the collection objective species, although I shall also include varieties and cultivars whenever possible. I've also included A. utile which isn't on the IAS list, presumably because it's sometimes thought to be a synonym for A. griffithii, but which the latest research recognises as a distinct species._[15]

 Distribution 

The map below shows the global distrubution of the genus 'though some populations are very limited.

[By Ninjatacoshell - This file was derived from: BlankMap-World6.svg: , CC BY-SA 3.0, Link]

The largest group is found in Asia where they grow from the Himalayas through China to Japan and south to India and South-east Asia . They are also also found in the Middle East, East Africa and there are four species in North & Central America.

 Classification 

There are several Taxonomy keys available either for the genus as a whole or for plants from particular loctions.{Flora of China, [FoC],_[1] Ohi-Tomai, Wu, H Murata and J Murata, [O-TZMM]_[15] S Renner, L-B Zhang, and J Murata, [RZM],_[16]}

Guy & Liliane Gusman, Eric Gouda, Pim Bongaerts & Joost van Gijn have perhaps the most comprehensive key in their, "Key to Arisaema species of the world"_[17]

The genus is traditionally divided into a number of sections. However, there is no general agreement as to how many sections there should be.

"...most of the sectional classification, go back to Engler (e.g., 1879; our Fig. 2), who gave much weight to leaf shape (diagrams of most species' leaf shape: Gusman and Gusman, 2002). Based on new anatomical and morphological data from living material, Hara (1971), Murata (1984, 1990b), and Gusman and Gusman(2002) made major modifications to Engler's system..", (RZM, p. 885, 2004). They used 11 sections for their sampling but the results suggested that there should be 12 sections.

FoC, (2010), has taxonomy keys for 12 sections.

O-TZMM, (2016), recognise 15 sections of Arisaema and, on the basis that this is the most recent document I've found, I shall use these pro temp; but in the belief that this number is likely to change in the future. Their paper shows a table, (Table 1), of various sectional divisions of the genus from Engler, (1920), to Murata et al, (2013). Their fifteen sections are shown below with the Type species for each section.

The O-TZMM sections,

The above considerations lead to the table below which lists the collection target species, together with their section code and name. Any Section Type species are shown in bold.

The Collection target species,

 Reproduction 

Arisaema have three methods of reproduction, from rhizomes, from stolons and from seed.

 from rhizomes  Several species develop rhizomaceous offsets on their tubers. These can be detected by a small leaf growing in close proximity to the main leaf/leaves.

 from stolons  A small number of species send out stolons so that the plant eventually forms a clump.

 from seed  Arisaema are very unusual with regard to the production of seed in that the majority of the plants change sex: some up to five times duting their lifetime!

Most young plants are male but, as they mature they change to female. This change seems to be dependant not only on the genetics of the species but also on the size of the local population and the availability of nutrients. _[18]

Pollination is carried out by Fungus Gnats, (genera: Sciaridae, Mycetophilidae, Dolichopodidae, Phoridae or Keroplatidae), _[19] When a gnat flies into the male flower it makes its way down the spadix, picking up pollen as it goes. When it finds itself at the bottom of the flower, there is a small hole through which it can escape. If it then repeats the process with a female flower, it spreads the pollen on the stigmas. Unfortunately, when it reaches the bottom of a female flower, there's no way out! _[20] However, we've noticed that some female flowers have a small hole chewed through near the base and it may be that some of the fertilizers create their own exit!