Mikes Exotics and Hardy Plants

Arisaemas, are interesting and complex members of the Aroid family.
Usually the preserve of the alpine and woodland plant enthusiast, the renewal of interest in growing exotics, has seen Arisaemas "Come in from the cold" with more people than ever growing them.
In the past twenty years or so, there has also been a flurry of new introductions, bringing even more species to the attention of the exotics enthusiast.

Although they're distributed widely throught the world, here in the West, we fare poorly, there being just a few noteworthy species.
It is the Far East that provides us with the bulk of the species we grow, including those known as "The Whiplash Arisaemas", with the Himalaya, China, India and of course Japan all being home to many fine plants.

Usually regarded as woodland plants, given some light or dappled shade and moisture, they'll grow almost anywhere.
I've seen them growing on the shady side of rockeries and I've grown A.Triphyllum and A.Consanguineum in a part shaded scree bed, with A.Candidissimum in a sunnier spot.

There are some doubts, about the hardiness of some of the plants I mention here, but in my garden they've all proved to be hardy down to -10c.
Deep planting and a heavy precautionary mulch, takes care of the winter.
However, early risers might get nipped by frost.
For gardeners who live further South than Birmingham, I'd expect all these species to be hardy, further North, the opposite and some may well need lifting and storing for the winter.

Good species to start with are, A.Amurense, A.Candidissimum, A.Consanguineum, A.Costatum, A.Flavum, A.Triphylum and A.Jacquemontii.
Species which may need protection or lifting include, A.Elephas, A.Engleri, A.Griffithii, A.Speciosum, A.Sikokianum, A.Tortuosum, A.Nepenthoides.
There are many more species available, but I think there's enough here to keep anyone going for a year or two.

Growing Arisaemas in pot's, gives you the opportunity to get a close look at these unusual plants.
It's also the best way of bulking up small corms which have been grown from seed or retrieved from around parent plants.
Deep crock pots are the best to use, with those known as "Long Toms" being ideal.
Always use pots which are large enough to give the corms room to grow.
Flowering size corms, should be planted approximately two thirds of the way down the pot, small corms, about the same or slightly less.
Remember, Arisaemas root from the top.

Most people say you should use an acid to neutral compost, but I've always grown them in whatever I've got available at the time.
Commercial orchid compost, as sold by Levingtons and J.Arthur Bower is o.k. but extra bark chips or Perlite should be added to improve the drainage.
Also good is one part coir, one part well rotted manure and one generous part of bark chips or Perlite.
To these mixtures, I also add long life fertilizer and charcoal pieces.

Far more important than which compost you use, is drainage, this must be excellent.
The corms of some species, seem to be more prone to rotting than others and excess water hanging around should be avoided at all costs.
At the risk of repeating myself, always err on the side of too much drainage rather than too little.
I don't use grit or gravel in my Aroid compost's, nor do I rest the corms on the stuff.
Aroids have a relatively soft outer skin and it is easily punctured by sharp edges.
Stick to Perlite or bark chips.

Once potted, they should be kept in a cool shaded area.
Don't water the pots when the corms are dormant, wait until you see the growing point emerging through the soil, then give them a very modest amount of water.
As growth continues, move the pots into better light but avoiding strong sunlight. Give more water and start adding fertilizer.
For flowering size corms, I use liquid tomato fertilizer, for bulking up small corms, I use liquid high nitrogen fertilizer.
I dilute my fertilizer to one third full strength and give them a feed at every watering.
It's beneficial, to keep the plants growing for as long as possible but once the leaves begin to die down, stop watering and feeding immediately.
When corms are fully dormant, return the pots to the cool shaded area again.

There are two ways of planting out Arisaemas, or for that matter, any bulb or corm.
The method you use, depends on whether you want to retrieve offsets.
If you're not bothered, use method one.
If you want to retrieve offsets, use method two.

First, choose your spot where the corms are to be planted.
Dig a fair sized diameter hole, at least 9 inches deep.
Don't skimp on this it's important.
Really loosen the soil at the bottom, excess water must drain away.
If you want to put anything beneath the corm, use Perlite or bark.
Refill the hole, with a mixture of soil, well rotted manure if available and long life fertilizer.
I normally put in a marker stick at this point so I know where the corm is.
If you're planting corms in the shade of say, a palm or tree fern, then do it when they're dormant and try not to do to much damage to their roots.
Even better, plant them at the same time as the shrub, palm, tree fern or whatever.
At this depth, the corms should be o.k. through the winter.
If your a bit unsure though, simply cover with a heavy mulch and that should do the trick.

This is the method I've used, for planting bulbs and corms, for well over twenty years.
It makes use of the plastic baskets that you grow pond plants in.
Its one great advantage is, that it makes collecting offsets very easy.
You simply have to dig down to the basket and lift it out, complete with offsets in situ.
The only downside, is that you can't really use it around other plants, as the roots grow through the basket making it difficult to retrieve without causing any damage.
As with method one, dig a deep good sized hole.
Place the basket in the bottom, put the corm in and finish of as method one.
(I usually make a couple of handles, using some strong wire which, when attached to the basket, make lifting it out even easier.)
That's all there is to it.

Growing Arisaemas from seed is easy, other than a soak in water for a day or two, they need no special preparation.
It also gives you the opportunity, to grow species which are expensive to buy as corms, or are not easily available commercialy.
The downside of course, is that you have to grow them on to flowering size yourself, between three and five years usually, which probably doesn't appeal much to todays "instant gardener".

Autumn through to Spring are the best sowing times and all that you need, are your seed, some pots and a well drained mix of your favourite seed or potting compost.
Soak the seed for a day or two, giving them a swish around in fresh water occasionaly.
Fill the pots and plant the seed, I usually put mine in at between a quarter and half an inch deep, depending on the size of the seed.
Place the pots in a tray and fill with water.
When the pots feel heavy, remove them and allow to drain.
Cover the pots with plastic bags or put them in a cold frame, unheated propagator or on shady window sill.

Germination is erratic and can take several weeks.
When the first seedlings show, remove the cover and move into better light.
I keep mine in the same pots for two years, which gives the young corms a chance to put on a bit of growth before moving them on.
As the seedlings grow, feed on high nitrogen fertilizer.
Don't over water, this can be lethal, the compost should be just moist.
After three years, I switch to liquid tomato fertilizer to encourage the corms to flower.
When they've flowered once in their pots I plant them out.

To grow on from corms, is even easier.
You can leave the corms around the parent plant to build up to a decent size or you can remove them when they're small.
Which ever way you choose, grow them on as outlined above.
You can, actually "force" the corms, so that you cram two years growth into one but this is a bit involved so I'll leave it out.  Posted by: Mike.