A lot of tropicals have evolved to funnel water off their leaves... AND I know, living in a dry mediterranean climate that tropicals NEED that wetness... it's awful hard for me to provide that kind of humidity... to even get close, I have to have a greenhouse.

I have a misting/watering system in my covered greenhouse. I have aroids, carnivorous, begonias, philodendrons,orchids etc in there. Even in the tropics it can get 'very dry'.
In fact where we live, we haven't had rain for months! Some plants, crotons, scheffleras, are fine, but most others 'revel' in the misting.
Banana need the moisure as well. In fact, if it gets above a certain temp. they stop growing. In a wetter area, bananas will grow twice as fast

My climate is tropical. Does that make it already humid enough for the plants, or would they still benefit from constant misting? I'm just a little concerned about airborne pathogens such as rust on my cannas. I wonder whether it's better to *not* spray and discourage diseases, or to spray and encourage plant growth.

My cannas don't receive any 'extra' water all all. Mostly, because where they are planted, there is no taps/hoses!
My proplem, here is with the wind. The cannas down the driveway are protected, somewhat. But in the planting bed they get a 'real blast'.

I am FAR from an expert in tropicals, but I can't imagine rust forming on plants in their natural environment. Here in the States I get rust on rose leaves in the winter... but I think it's because it's not cold enough to inhibit the rust fungus.
I't THINK that tropical plants have evolved to deal with constant dampness. It may be 'dry' but dry is relative... up until last week, We here in Sacramento had like 2" of rain for the year... :) And I know that the plants that are native here would probably get some kind of fungus, if they could stay alive, in the tropics. But I highly doubt that tropiccal natives would, or they never would have evolved. Some types of canna are called 'water cannas' so they've definitely evolved to tolerate a lot of water.
I wouldn't worry about it... if some kind of fungus grows, it's pretty easy to take care of.

Hi
You live in Malaysia and you don't have heavy rainfall??
I thought that whole area was either wet or underwate!! lol Are you high altitude or between mountains.??
The only thing I've ever seen kill Canna is hard freeze and drought.. They love water and should flower year around in your area.
Have always wanted to visit there. Tell us what it's like in your area?? gary

I think that your question has 2 answers.

You say in your header that you live in the "Tropical Rainforest". And its true that a lot of the acreage in Malaysia (and a lot in Costa Rica, and Ecuador, and Borneo, etc) IS in fact covered with tropical rainforest. But living in a tropical CLIMATE, and actually living IN the Rainforest, are 2 entirely different things.

Plants that are native to the rainforest have adapted certain features in order to not "drown". The forest floor is supposedly actually fairly dry...its not a huge bog anyway, but its moist and humid. But supposedly, the hard or heavy "flooding" rainfall per se never really reaches a lot of the plants on the forest floor. The tree canopy is so high that it catches a lot of the water, and from there it "trickles" down gently.

That is why certain plants like some anthuriums, bromeliads, and orchids have evolved as epiphytes who grow up in the lower canopy...to catch the water as it trickles down in their cups or on bare roots.

As Heathen said, many plants (especially aroids) have developed leaves that funnel water off and don't allow it to collect in the leaves and axils, where it would cause rot or disease.

And in everything I have ever read about heliconias, the largest stands are always by river banks, and in fact, they tend to "start to take over" in areas where the forest canopy has been destroyed, thus letting in more light and rainfall that hits the ground.

For plants that you are growing in your YARD (as opposed to the actually plants out in the rainforest) you may well need to supplement water, but your humidity should be good enough. These are not really in their "natural environment", even though they are in their "natural climate".

>heathen1
I think your point is correct when it comes to most tropical plants and fungal diseases but I believe that the canna-rust pair is an exception. I have yet to see a single canna grove that has not been infected by rust to some degree. Some are so badly affected that they look as if they were hit by a small hurricane. Granted, the rust is not fatal due to the canna's vigorous growth. However, it does detract from the pretty foliage and blooms.

>garyfla
You're right about the heavy rainfall, but the only time when it stays consistently wet is during the monsoon seasons twice a year. At other times, the high temperatures (30 deg Celsius and above) ensures that most excess moisture dries up real fast. I'm not concerned about the cannas receiving lots of water at their roots; I'm just wary of encouraging rust infection by keeping foliage wet. Do tell me if you plan to make a trip to Malaysia. I live near the capital (Kuala Lumpur) and would be more than happy to show you around!

>bihai
Thanks for pointing out my mistake. I do live in a moist tropical climate, but not the rainforest per se, hehee. What you said about heliconias is true for cannas here as well: they really take over any patch of land they're grown on. In fact, the only controlling factor seems to be....the rust!

hello
i only grow one clump of Canna due to leaf roolers ,an insect that decimates the leaves. Heliconia seem immune to it so i mostly grow those instead.
I usually just whack them off when a pest problem comes along within a month they're flowering again lol. Rust does not seem a big problem for me.Poor soil is so i grow them in enriched beds or standing water because our winters are so dry.Have never noticed any problems with wetting the foliage. Are you growing the fancy leafed varieties??
As to the invitation to visit I'm packing my bags as I write this lol But probably not; though I'll pass along the invitation to my doctors they have most of my money and want even more . need to repair the house etc. etc. lol.
Would sure be fantastic,have many plants from that area.
thanks gary

I've heard about the leaf rollers. A swarm of them just decimated my bamboo during the last monsoon, but my cannas have not been attacked so far. And no, I don't grow the fancy-leafed varieties, not because I don't want to, but because they're quite uncommon here - except for the one with yellow-striped leaves and orange flowers which grows everywhere! Admittedly, most of my cannas are dug up from the roadsides. I often go canna-hunting to collect specimens with rare/pretty blooms.

I grow all my grounded plants organically, and am beginning to think that badly rusted cannas are a sign of unhealthy plants due to poor soils and synthetic fertilizers. Perhaps my concerns about wetting foliage were unfounded after all. I guess plants can pretty much take care of themselves as long as we provide them with good growing conditions.

I stopped planting new cannas because of leaf rollers. I ****HATE**** them. They decimate my cannas every year. There are so many nice cannas I would like to grow. I splurged one year and bought the CLeopatra canna, a very nice variegated strain that was about $25, DECIMATED. I have observed that leaf rollers will travel from cannas to bananas if given the opportunity. I tried treating my cannas with Thuricide one season, but it was ineffective because the almost daily thunderstorms we get here in summer just wash it right off.

I never get rust on my gnawed on cannas, but frequently get it on my plumeria. It doesn't really seem to hurt anything, though, so I never spray with anything.