Natural growing; why do we repot so frequently?

[Leo Schordje]

I have a number of parvi's, the "bloom and die" phenomena is real, but it is avoidable. For me one cause of "death after bloom" is that while it is in bloom, I take the plant out of the growing area, take photos, show it around, take it to shows or judging. During this period, sometimes I forget to keep a close eye on the plant, and it gets too dry, or too cold, or too hot. I have killed a few plants just by mishandling them while they were in bloom. Dry the roots out hard, new root tips die, providing a site for pathogens to infect the plant, fungal or bacterial rots.

Another possilble cause of "death after bloom" is that the plant was weak going into bloom. For my parvi's, if the plant is a weak single growth plant, I routinely cut the flower bud off as soon as it is high enough out of the leaves to do so without damaging the crown of the plant. The sooner you remove the flower bud the more energy the plant puts into making the next growth. I know this is a horrible thought to most people, but if the plant can not be replaced, as is the case with collected material, you should really be concerned more with getting the plant up to size rather than seeing what the flowers look like. Seed propagated plants and hybrids, I do let bloom, because they can be replaced. I have bloomed and rebloomed at least 10 Paph emersonii (I have about 16 of them) and have only lost 4 of the original 20 I bought. Paph emersonii & micranthum are the species that forced me to start the flower bud pruning on single growth plants.

Those are my thoughts, hope this idea helps

 

[Rick]

Leo brings up an old debate on whether or not plants bloom only when in optimal health or plants bloom in a last ditch effort to propogate because optimal health conditions are not available.

(Both conditions may also be true).

Xavier took some soil pH readings around wild clumps of armeniacum and found that the pH near the center of the clump (of past bloomed growths) was lower than the pH around the new (unbloomed) growths where the stolons had pushed out too.

This suggests to me that some type of nutrient depletion or unavailability is going on around old bloomed growths, while stolons are actively "seeking" or passively "migrating" into nutrient available systems.

Logic to me suggests that if cutting a spike to "save energy" for more vegetative growth works in the long term, then either a key (or general) nutrients must be limiting.

This could be caused by a low pH environment as well as too much or not enough fertilizer.

In the case of the paph species growing on limestone / dolomitic cliffs, I would suspect that the pH environment is probably much more constant than in bark moss or CHC potting mixes in pots. Several of us debated an article in Orchids from several years ago about the use of lime in potting mixes being neccessary. The focus of the article was actually on Calcium, but I noticed pretty quick that the pH of unsupplemented bark mix dropped to very low levels over the coarse of the year, while pH held up pretty well with even a small amount of lime. If I remember the low pH plants grew very poorly in comparison but they may have made it to blooming anyway.

Not only is the pH fairly constant, but there should be a small constant availabilty of Ca, Mg, and PO4 coming off of most limestone based substrates.

When you look at the minneral content of plant leaves, there is typcially a pretty close ratio (moles or molecules) of Ca to Mg. However Ca once in a plant is pretty much there all the time. Mg is used in chlorophyl which depending on light and temp be a more "used up" commodity for plants, and may be a more limiting growth factor.

Bio availability of Ca and Mg is highly variable based pH competition between the two ions themselves, and the amount of other metals such as iron and zinc.

So going back to the emersonii/ hangianum issue, I think its a good strategy to use as much inert material in the mix that will still alow a final pH with irrigation water to stay around 6.0 - 6.5, and periodically spike with epsom salts during periods of faster growth. Most waters that people have for tap water already have 2-3X more calcium than magnesium. And then if you amend your potting mix with lime or oyster shell, you will push the ratio of Ca to Mg up even more.
Dolomitic lime can have a better ratio of Ca to Mg, but it is highly variable by source. So the periodic dose of Epsom salts should just bring the Ca to Mg in balance.

 

[Bjorn]

Anyone having any info on the chemistry of the limestone on which hangianum and emersonii is found? Is it lime or is it dolomite?
When I use dolomite in my mixes, its as dolomite, i.e. stoichometric dolomite with equal amounts of Ca and Mg (molar). This is also the stuff I added to the old micranthum planting in the picture at the beginning of this thread. Plenty of it. Perhaps as much as 1 part out of 5 was added as coarse dolomite (a bit like rather coarse sugar). So, at least that one had acess to plenty of Mg and Ca and the pH has probably been constant all these years.
One thing that I have noted is the reluctancy of many paph growers to incorporate plenty of limestone(dolomite) or oyster grit into the compot. Some of it is probably inspired by the warning in the books of the Bakers and Braem having warnings against putting limestone into the mix; allegedly because cold water dissolves limestone and the liberated calcium then would poison the plants. How can one imagine that plants growing directly on limestone (e.g. hangianum or helenae and most other parvis occasionally do) should survive the winter? Because it does get pretty cold there, almost down to freezing. And ok, even if it is not raining much, the plants are supplied by, amongst other sourses, seepage water, that according to this cold water theory should be poisonous for the plants.
Well, the idea about cold water dissolving limestone is not all wrong, actually its the dissolved CO2 in the water that dissolves the limestone, and cold water holds more CO2 than warm water. BUT, this also happens in nature, and in soil and the plants still survive.
In in a recent thread by Paphioboy on this forum http://www.slippertalk.com/forum/showthread.php?t=19262
he gave this link which is a link which includes Paphiopedilums in Laos with cultural recommendations:
http://www.orchisasia.org/especes/p/paphir/paphir_en.html
As a matter of fact, they recommend a mix containing 1 out of 4 parts of limestone.
By having cupious amounts of limestone(dolomite) in the mix, at least the pH (and phosphorous supply?) should be stabilised and also the supply of Ca and Mg(if dolomite is used).
Water is of course important in this connection, and while I do not have any experience using "hard" water, I think that rainwater or equivalent is the best approach after all.
Btw. there is one negative aspect about putting too much limestone into your mix - the pots get d... heavy.
Bjorn

 

[paworsport]

I have an old malipoense bought in 1990 form a nursery closed now in France. The plant was obviously not a selected but direct import. The plant is vigourous, flowers every 18 month but has not the habit to make stolon : only one new growth etc...

 

[Rick]

Averyanov describes a qualitative difference between the hard crystaline limestone that (I think) emersonii grows on and the soft, stratified limestone that (I think) hangianum grows on in Vietnam. Neither is listed as "dolomite" and mineral content is also not mentioned.

From looking through some geological sources, Dolomitic limestones are very common, and a special yellow dolomite is quarried in Vietnam.

The % amounts of Ca vs Mg in limestones and dolomites is more like a continuum rather than discreet forms, and the cutoffs are somewhat arbitrary. It's almost as bad as slipper taxonomyoke:oke:

Dolomites I believe tend to be softer and easier to disolve than high calcium limestones.

 

[Bjorn]

Averyanov only says something about Mg in soil when he describes alkaline soils. There he states that they are rich in Mg. The deposits of thse soils are according to the map adjacent(just south) to the limestone where hangs and emersoniis ++ are found. Can we , based on this, suppose that the limestone is rich in Mg?
Btw. Its impossible to see any difference between crystalline Dolomite and Limestone. Both looks like marble - at least the stuff I have is white, dense and with crystallites of perhaps 1mm, i.e. fairly coarse textures and probably slow to dissolve.

 

[TyroneGenade]

Hi,

The Leeanum experiment is under way. I took the plant out of it pot and was surprised to see a miserable rotting root system on a healthy plant. There were lots of new roots coming so I repotted as well in bark with some broken bricks and river sand and then into a smaller pot! (Not the direction I was hoping to go.) I cut off one piece of 3 growths which went into a small pot with bricks and leaf litter. As the bricks are alkaline in any case I figured there was no need for limestone.

So I have 2 experiments on the go... If both die then we know this isn't a way forward. If they thrive, then I can try something more picky about potting conditions.

 

[Leo Schordje]

About limestone, Rick, you are right. I used to work in chemicals for concrete industry. As you said, the chemical properties are on a continuum, there is no bright line between dolomite and limestone. About the hardness, & resistance to weathering, again the full continuum exists. Hardness of all types of limestone (including dolomite) is directly related to the inclusions of impurities, like silica, manganese, iron and other minerals. Dolomites high in manganese and iron can be very hard, as can nearly pure calcium containing limestone if it is high in silica and formed under favorable conditions. The second factor influencing hardness is the formation process, the number of times the parent material has been dissolved and re-crystalized and the pressure and temperature at which this happens. So it is possible to find the full range of hardness for both dolomite and for limestone.

 

[tenman]

I have two reservations about long-term growing without repotting. While it may work in isolated instances, the key fact that must be remembered is that plants in nature are not growing in a limiting plastic pot. The chief problem is that if there are any ingredients in the mix which can break down, they can often clog drainage holes, causing a serious problem and ultimately root death. As well, said breakdown may eliminate the possibility of aeration in the mix itself, also leading to root problems. Lastly, if you look closely, plants in nature are not growing in one location. That is, the plant moves on through time as it grows naturally, leaving the old dead and dying growths in the depleted area as its new gowths inevitably march on to new turf.

 

[Rick]

I have two reservations about long-term growing without repotting. While it may work in isolated instances, the key fact that must be remembered is that plants in nature are not growing in a limiting plastic pot. The chief problem is that if there are any ingredients in the mix which can break down, they can often clog drainage holes, causing a serious problem and ultimately root death. As well, said breakdown may eliminate the possibility of aeration in the mix itself, also leading to root problems. Lastly, if you look closely, plants in nature are not growing in one location. That is, the plant moves on through time as it grows naturally, leaving the old dead and dying growths in the depleted area as its new gowths inevitably march on to new turf.

Some of the same logic I used to using the slat basket instead of pots. Many of my most successful non slipper orchids are mounted or in baskets that I just top up with fresh moss periodically. Many paphs are cliff dwellers growing a lot like epiphytes with roots totally exposed, so why not treat them more like more other epiphytic orchids?

 

[Bjorn]

Tend to agree with Rick above. If we are to change the growing regime towards more "Natural" growing, one typical move would be to look at the pots. Aeration is probably an important point. When it comes to decay etc. a potting mix based on inorganic "structure builders" like expanded clay, limestone etc. with organic material as supplement and nutrition for the roots could be a starting point. A rough guide for the proportioning of the structure is that monosized material generally packs to approximately 50%. I.e. if Leca is poured into a container, then approximately 50% of the occupied volume is Leca, the rest is voids. These voids can accomodate finer stuff and so on, and astonishing packing densities can be accomplished by careful packing. For orchids we would like to have porosity though, and should therefore leave room for the roots. I would expect that the most serious problem is connected to the size of the plant, particularly for large plants with massive roots. I strongly suspect that after some time an undersized container will be full of roots, some of them die after a time, and if the container is too small, the conditions get stale and the root die-off spreads.
Managing the whole concept (that is growing with a minimum of re-potting) gets much easier with moderatly sized plants.

 

[tenman]

Some of the same logic I used to using the slat basket instead of pots. Many of my most successful non slipper orchids are mounted or in baskets that I just top up with fresh moss periodically. Many paphs are cliff dwellers growing a lot like epiphytes with roots totally exposed, so why not treat them more like more other epiphytic orchids?

One difficulty in replicating the natural environment is that those cliff-dwellers are subject to almost constant seepage of moisture past and over/under their roots. In culture we are mostly limited to watering in intervals and keeping the substrate moist to allow the constant uptake of water they are used to. Growing Disas in a flowtable simulates their natural environment more accurately than most other methods of growing orchids I have seen. Of course, a paph isn't going to want its roots submerged all the time, either. So perhaps mounting paphs slantwise on a rock with some detritus loosely under/over the roots and then having a drip tube attached to allow for a constant but minimal amount of water (rainwater, of course) to seep down the rock would be close. But what a pain to set up, and then there's the runoff to consider...

 

[Rick]

One difficulty in replicating the natural environment is that those cliff-dwellers are subject to almost constant seepage of moisture past and over/under their roots. In culture we are mostly limited to watering in intervals and keeping the substrate moist to allow the constant uptake of water they are used to. Growing Disas in a flowtable simulates their natural environment more accurately than most other methods of growing orchids I have seen. Of course, a paph isn't going to want its roots submerged all the time, either. So perhaps mounting paphs slantwise on a rock with some detritus loosely under/over the roots and then having a drip tube attached to allow for a constant but minimal amount of water (rainwater, of course) to seep down the rock would be close. But what a pain to set up, and then there's the runoff to consider...

I tend to over water (something daily), and keep air humidity very high. My present mounted and basket stuff stuff does great, which was another consideration in moving my cliff dwellers to the baskets.

So far in the first month things are going great. I'm particularly impressed with the growth of some roth seedings so far. My adult stoneis are showing new growth and roots, and I'm seeing new root growth in sanderianum seedlings.

One or two years from now I might be cursing this system, and everything seems to work good for a couple months, but we'll see.

 

[cnycharles]

.... So perhaps mounting paphs slantwise on a rock with some detritus loosely under/over the roots and then having a drip tube attached to allow for a constant but minimal amount of water (rainwater, of course) to seep down the rock would be close. But what a pain to set up, and then there's the runoff to consider...

if you had a reservoir at the bottom, put a small aquarium pump there and pump the water back up to the top

 

[tenman]

I tend to over water (something daily), and keep air humidity very high. My present mounted and basket stuff stuff does great, which was another consideration in moving my cliff dwellers to the baskets.

So far in the first month things are going great. I'm particularly impressed with the growth of some roth seedings so far. My adult stoneis are showing new growth and roots, and I'm seeing new root growth in sanderianum seedlings.

One or two years from now I might be cursing this system, and everything seems to work good for a couple months, but we'll see.

Keep us posted; it'll be interesting to see how they do. Good luck!

if you had a reservoir at the bottom, put a small aquarium pump there and pump the water back up to the top

Yes, but the water wouldn't be fresh for long, going through the crap around and under the roots. I like the 'drip' idea, but it would be monumentally difficult for a large collection of paphs, and you couldn't share the water between them for fear of spreading things. I know it's risky even with the couple dozen disas I have, but it's the only way I can manage them. I know several folks who have had problems with spreading fungus/bacteria among an entire collection of disas thusly and lost most of them. I think I've reduced the chances of that substantially by switching to straight diatomite as my medium for them, but it still concerns me.

 

[Ernie]

Tenman, ever consider adding a UV sterilizer to your recirculating water? You can find inline and submersible ones on eBay for under $50 (I'd guess a 9 watt unit would work for you).

 

[valenzino]

Remember that in the natural environment plants die daily and only few reach specimen size....the goal of the plant is to produce seeds once.
Growing plants to big size is a human behaviour...
I agree about air in the roots and less repotting possible...
but depends on many different topics.
Exaple,leaf mould growers use to run ...so yearly repotting is better...strap leaves ones...is better to repot less often.
Few Paphs have "underground roots",usually are on the surface and run far away from the plant...very good air qty...
My opinion is best to try "thick net pots" with semy inorganic media and disturb less possible roots while repotting.

 

[cnycharles]

Tenman, ever consider adding a UV sterilizer to your recirculating water? You can find inline and submersible ones on eBay for under $50 (I'd guess a 9 watt unit would work for you).

ah, I thought of this, this morning when at work... have supervisor who has had many fish tanks and talks about all the bells and whistles. also some apple cider producers use these systems for sterilization, as well as more greenhouse and nursery producers who must re-use their waste water as they have very strict water use requirements in their states or localities. in central ny there are no use requirements like this since we seem to have a high level of rain and snowfall each year (and plenty of clouds when it's not actively precipitating)

 

[Rick]

Remember that in the natural environment plants die daily and only few reach specimen size....the goal of the plant is to produce seeds once.
Growing plants to big size is a human behaviour...

I would agree if you are talking about seedlings primarily.

There are many species of plants and animals that have not adopted the salmon or octopus model of dieing after their one and only reproductive event. I disagree that slippers are more like annuals and ready to crater after one seed production event (even though I realize that any given growth blooms only once). We seem to see multiple cases where many paphs seem to not want to flower until they have acheived at least a few growths in a pot. In particular I think you have reccomended not dividing roths until multiple growths are achieved.

I think we've all seen plenty of in-situ pics of huge clumps of many adult slipper species that would suggest that big multigrowth slippers are not strictly a GH (human) phenomena.

Given the low succes rate of polination and seedling survival, at some point in plant age (size), slippers must be pretty durable for years on end to keep from going extinct.

 

[Bjorn]

One comment to the water issue: I have a rather extensive collection of Dendrobiums mounted on bark. Before I got my greenhouse some 15 years ago, I grew them indoors, mounted on a wire-mesh. Because of this and because of extensive travelling I installed a drip-irrigation system on the slabs with a tray to take the excess water. The drip-irrigation worked nicely in combination with occasional misting and the excess water was almost in balance with the evaporation, i.e. I had to empty the collecting tray only occasionally. This shows that it works. It is however most certainly dependent on pure water, rain or R-O or at least "soft" water due to evaporation from the roots. This was for dendrobiums. Now , In the greenhouse, I spray everthing down with a hose, and that is of course much easier.
My paphs grow either in baskets or pots. The baskets are rather large for the size of the plant so commonly its used on small species, often several of them together, like the pics in the first entry of this thread. The soil that I am using looks quite "gravelly" i.e. gravel with organic matter (bark, moss, minced twigs etc. The gravel consist of mostly dolomite and marble, but also perlite, expanded clay and plain sand. Top dressing may be done with decayed leaves, bonemeal etc, but first of all, moss growing on the surface is sought for. This is only happening if the surface is quite moist, so my watering regime might be a bit different from others. I try not to overwater but still keep surface moist - This is to mimic dew. I rarely flush the pots, but every morning the surface is sprayed, and the humidity is kept at 70% and above (70-95%) during daytime, and during night it raises to >95%. After the lights are off, frequently a thin fog fills parts of the greenhouse, but without excess moisture to the plants.
If the moss grows, everything is fine, if it dies off then obviously something is wrong. It could be the fertiliser being too strong, seems as the limit is around 250ppmTDS for healthy moss. Too much moss is not good either so occasionally some might be removed. This is mostly done for small paphs in baskets. Btw. these are not hanging baskets, Just rectangular basket like plastic boxes with ribs on the sides, intended to store things in. Most of the larger paphs are in regular pots, but I am slowly converting them from standard mixes to more long lasting attemts like the one described above.