Delighted by A. dahaiense

Not all flowers are beautiful, but my goodness arisaemas have curious flowers and equally peculiar propensities.

Arisaema ringens has been around New Zealand gardens for a long time – sometimes called Jack-in-the-pulpit though that is more correctly used for the American species, A. triphyllum. While A. ringens has handsome, glossy foliage, the flowers hide beneath in such seclusion that you are likely to miss them entirely.

The last twenty years have seen an influx of new Asian and Japanese species to the country, many of which have piqued the interest of collectors. Even now, the choicest ones are difficult to source – often more a case of who you know rather than where you can buy them. And if you get hold of them, some are very difficult to keep going, especially in garden conditions as opposed to nursery pots.

Arisaema tortuosum

Not all are devilishly difficult. A. tortuosum is easy and will seed down freely, a bit too freely, we find.  It makes a big patch, maybe 75cm tall, with the green hooded flowers sitting above the foliage. We find it is perfectly happy in the border right beside the house on the eastern side where the only water it gets is run off from the adjacent path.

Arisaema speciosum

A. speciosum is another easy variety in semi shade. It has handsome foliage, lovely mottled stems and curious flowers in burgundy-brown that really do look like hooded cobras. But the issue is that the flowers are held beneath the foliage so unless they are planted on a slope or on a margin where you can see into the patch, you may miss the flowering season. The early summer blooming A. candidissimum is one of the prettiest forms and is not difficult to grow with its palest pink and white hooded blooms appearing before the foliage dominates. It also multiples well.

Mark’s A. sikkokianum hybrids

And then there are the tricksy ones, few more so than the Japanese A. sikokianum with its phallic spadix and hooded spathe rising prominently above the foliage. It is a show stopper in spring, though definitely curious rather than beautiful. After many years of growing it, I can tell you that it is difficult. We have never seen it increase from the corm. Growing well, it will set seed but these need to be raised in controlled conditions because it will not seed down naturally here. Even then, the patches tend to get smaller with time, rather than larger. It was for this reason that Mark experimented with hybridising it, to try and get increased vigour. This is known as hybrid vigour, in a similar way that the controlled breeding of designer dogs can make the offspring a stronger genetic strain than the highly refined parentage of pure breds. It has worked for us. The offspring carry all the best characteristics of A. sikokianum but they grow more strongly and are reliable as garden plants. Few would pick the difference to the lead species, but we know they are actually hybrids.

Arisaema dahaiense

For sheer bizarre appearance, the more recent acquisition of A. dahaiense has to take the cake. It is very peculiar and not a carnivorous plant, though it looks as if it should be. The mottled, frilly flange is particularly striking. Because we are gardeners rather than plant collectors, the fact that this large-flowered curiosity has settled down quite happily in the leaf litter of open woodland conditions is a real bonus.

Peculiar propensities?  Arisaemas are hermaphrodites. When they are young or growing weakly, they are male. Only when conditions are right and the plant is strong, do they become female and therefore capable of reproduction. Then if they need a wee rest, maybe after a season of prolific seed set or drought, they revert to male again. Is this a metaphor for the human condition, some may wonder. I could not possibly comment.

A. taiwanense seed

If you notice a vague visual similarity to the mouse plant (Arisarum proboscidium), the striped Arisarum vulgare or arum lilies you are correct. Though not close relatives, they are all aroids in the Araceae plant family. Arisaemas go dormant in late summer and grow from corms – often roundish balls or larger round discs, though speciosum corms can look more like something unfortunate that the dog has left behind. Some species set copious amounts of seed which can be attractive in itself in autumn, though it helps to know your species. I remove the tortuosum seed because it can spread too freely whereas the speciosum seed, while abundant, has not created problems for us.

If you really want to know more about this plant genus, the gold standard reference is currently still a book, a proper book, not the internet – “The Genus Arisaema” by Guy and Liliane Gusman.

Arisaema candidissimum

First published in the December issue of NZ Gardener and reprinted here with their permission.