Air Circulation

[lamwn]

Hi all,

I have been thinking quite a bit on this thing about air circulation recently, and got to hear the views of many experienced growers on this too.
Unfortunately, I could not conduct any 'private experiments' to find out for myself , so I figured the best way would still be to discuss it on the forum.

As we all know, stagnant, humid air encourages fungal growth and rot. Air circulation prevents this, as well as keeps CO2 concentrations around plant foliage higher by replenishing it from surroundings. It may also help cooling plant foliage if there is water on the foliage or simply due to transpiration (though this of course causes water loss for the plant!)
However, too much air circulation causes RH to drop and may result in high water loss from plants.

What I was interested in finding out is how much is good, and how much is too much. And maybe even what species particularly dont mind sacrificing some RH for more air circulation.

In addition, I would like to know if anyone could share experiences on the following...or even better still, conduct a small scale experiment with the following factors:

(i)Strong air circulation in the day (when plants photosynthesize), weak air circulation at night (when they dont)
(ii)Extremely strong air circulation, but in an enclosed system...for example, strong fans but no ventilation windows in a greenhouse, or small fan units in an enclosed terrarium.
(iii)Dry winds

Thanks in advance for all inputs.
Lam

[rainforestguy]

Lam,
This question is a difficult one to answer for all species/hybrids to make generalizations. The main point to make here is that not all species/hybrids grow the same. Wind, drier air actually makes tougher plants. If humidity is too low, pitcher size and even development will be compromised. We should always look at nature. We have seen plants growing in very hot regions, often perfectly in full sun, but when we look deeper at their roots, we find a water table. On another hand, we see plants growing in deep ravines and crevices and seemingly on pure limestone. Others are epiphytic in nature and grow on trunks and stumps where moss and other debris collects.
Plants are best when found growing in exposed sites, with their viney tips always exposed to harsher wind, sun and the elements. The ability of upper pitchers to coil, grasp and cling to anything suggests that they are probably adjusted to seasonal/monsoon or even storm conditions. Anyone trying to pull to cut a leaf or stem discovers how permanent they really are and do not break or detach readily. These suggests to me that wind is not an issue for them. One of the greatest adaptions in some species is the almost enclosed lids (i.e. N. clipeata) where plants grown on precipices and vertical conditions allows them to remain steadfast and able to grow despite gusts of winds exposed on a daily basis. These plants while not really vines, do scramble and grow among the cliff vegetation and outcrops.

My own experiences suggests that these plants adapt readily so long as other variables in water match them accordingly. Plants exposed to very windy areas need more water than those grown in stagnant, or protected areas. Plants exposed to these dramatic conditions tends to grow well and adapt or modify leaves, pitchers and stems to accommodate these growing needs.

Other plants actually like it drier. N. veitchii has been best grown in drier conditions. Whether this is due to their adaption for growing along trunks of trees or just due to their regions, plants actually grow better drier than soaking wet. My best veitchii's are grown in areas where a wind tunnel exists. Neighboring veitchii hybrids also show a preference for these drier conditions.

N. bical has had difficulties growing in very windy and exposed regions, but they do adapt. Pitchers tend to be smaller and harder than their siblings grown wetter, shaded.

There is no cut and dry method to make plants adapt, but when exposing plants to drier/windier conditions, wetting the plants and soil, roots is of utmost importance.

Michael

[kinabalu]

Hello,

I'm new on this forum, and i like already it. So nice to meet you.

Here is a very interesting subject.
Some nepenthes like pervillei or madagascariensis grow in open areas. When i've been in si-tu, humidity was quite low during the day. Hot days, but a lot of air.
So since some weeks i'm using a little system in one of my terrariums for pervillei for exemple, and it works better than before with high hmidity during daytime. The plant looks stronger, with green light leaves. It's growing in pure sphagnum, with a dryer soil between 2 watering. ( The plant is quite small )
So i think air circulation is a must for a part of nepenthes, and important too.

Best regards,

Kina.

[rainforestguy]

Most people (and commercial growers especially) make the mistake and say that nepenthes require high humidity, yet their companion plants in the wild do not. Nepenthes also grows with various epiphytic orchids, ferns, hoyas and various epiphytes/natural ground dwellers, but you don't always need to maintain high humidity for good development.
The idea of growing them in LFS and other wet soil substrates seems odd when natural wild populations of nepenthes usually are found in granite, lime, and clay soils many times without even organic components present.
I believe the way we are growing nepenthes (mostly from literature and growers' accounts) tend to be misleading and full of deception. Nepenthes actually grow better in media with more porosity and where water can freely drain through. Comments in the past have lead this discussion to saying that they require the oxygen from free moving water and that water must be diluted with lime residue or even acid solution. The point we are missing is that they require free water to flow through their roots as they have adapted growing in this manner and expect the same.
Getting back to air circulation. Most wild naturally grown nepenthes are almost always found exposed to good air circulation or even under-breezes that occur in the canopy and shaded communities. Air circulation is a must!

M

[agustinfranco]

Hi all:

This is a very interesting topic for discussion. Rainforest has a very valid point, exposed plants make tough plants, but these have to be a bit more adaptable to begin with in order for them to grow tougher.
Also there are some plants which can grow under low humidity ie, ventricosa, maxima, truncata and a wide range of hybrids. Others will not pitcher unless a minimum humidity level is met ie, ephippiata

circulation of humid air is far more useful than circulation of dry air.

Gus