About fertilysers for Slipper orchids.

[Ray]

Lance, I find your responses to be very thoughtful and astute - except for the last sentence in your reply to me. <insert grin here> Sorry for taking things wrong.

Re Physan: I have used it as an algae preventive on greenhouse glazing and drench pots. The labels says 2 teaspoons per gallon for rots, but I have seen the occasional damage in seedlings at that rate, so try to limit it to no more than one.

A commercial grower I know adds minute amounts to his irrigation tank - I think he mentioned it being in the neighborhood of a teaspoon per 20 gallons, or something like that - and commented that he has seen no botrytis, and a huge reduction in all rots.

As an experiment, I have added some to my fertilizer concentrate tank @ 1 tsp/5 gal to see if it will keep the bacterial sludge at bay (yes, but not completely - maybe I should increase that), and I can see no issues with the plants, since it is diluted 128:1 from there.

 

[gonewild]

Thanks for the interesting discussion on watering. I've had a major concern with water sitting on leaves through the night as we've moved into November and December. My main heat is in floor, which is great for maintaining high humidity, but the leaves do not dry out before evening, which is at 4:30 PM, now, here in central Minnesota. I've taken to running the back up LP gas heater to dry things out. It seems to be working.

Unless your night temperature is lower than the plants optimum temperature water simply sitting "on the leaves" should not cause a problem. Water in the crowns of plants like Phals would be a problem however. Running your heater in late afternoon to help dry the water is a good practice. You can probably get the same results by running a strong fan without heat to dry off the foliage.

Since moving into the greenhouse in September, I've already noticed the Paphs perk up. I'm sure some of this is due to natural light, but, as Lance has mentioned, I also believe that the whole plant getting doused with water has helped, too. When I was growing in the house, the water was directed CAREFULLY to the media to avoid splashing water on carpets. The leaves rarely got wet. Plants grew and bloomed OK, but I never felt they were at their best.

Yes!

 

[Erythrone]

I have had a few bad experiences with Physan so I don't use it anymore.
I would still use it as a cure but not for prevention or substitute for more air circulation.

Me too. I prefer cinnamon extract. (hot water or alcool. Thanks, Ray, I took the idea on your web site)

But I use similar products (Quat) for cleening the room, but no longer on plant.

 

[Ross]

Unless your night temperature is lower than the plants optimum temperature water simply sitting "on the leaves" should not cause a problem. Water in the crowns of plants like Phals would be a problem however. Running your heater in late afternoon to help dry the water is a good practice. You can probably get the same results by running a strong fan without heat to dry off the foliage.

I have two, soon to be three HAF fans running constantly as well as a couple small fans in the corners that were temporary. I'm using an old pedestal fan until the other fan arrives. Even with all this air movement, things dry out slowly, now that the exhaust fans are shut down for the winter. I believe it is due to the high humidity caused by in floor heat evaporating water into the air, and poor air exchange due to the tightly sealed construction done to save heat. Do you think another method of air exchange would be helpful, and if so, any suggestions?

 

[Erythrone]

Lance, I find your responses to be very thoughtful and astute - except for the last sentence in your reply to me. <insert grin here> Sorry for taking things wrong.

Re Physan: I have used it as an algae preventive on greenhouse glazing and drench pots. The labels says 2 teaspoons per gallon for rots, but I have seen the occasional damage in seedlings at that rate, so try to limit it to no more than one.

A commercial grower I know adds minute amounts to his irrigation tank - I think he mentioned it being in the neighborhood of a teaspoon per 20 gallons, or something like that - and commented that he has seen no botrytis, and a huge reduction in all rots.

As an experiment, I have added some to my fertilizer concentrate tank @ 1 tsp/5 gal to see if it will keep the bacterial sludge at bay (yes, but not completely - maybe I should increase that), and I can see no issues with the plants, since it is diluted 128:1 from there.

Thank you Ray. I forgot to say that I still use it for humidifier. I wonder if it can react with salts when mixed with fertilizer? And does it change pH?

Yes, I read that similar product (Kleengrow) are effective against Botrytis cinerea, fusarium (tomato, cucumber, etc) and other diseases. Efficient against some virus too.

 

[gonewild]

I have two, soon to be three HAF fans running constantly as well as a couple small fans in the corners that were temporary. I'm using an old pedestal fan until the other fan arrives. Even with all this air movement, things dry out slowly, now that the exhaust fans are shut down for the winter. I believe it is due to the high humidity caused by in floor heat evaporating water into the air, and poor air exchange due to the tightly sealed construction done to save heat. Do you think another method of air exchange would be helpful, and if so, any suggestions?

What is the humidity of the outside air?
To dry the foliage you have two basic choices... raise the air temperature or lower the humidity of the air.
As odd as it sounds letting in some outside cold air might be cheaper than just running the heaters. If the humidity is lower outside bring in some of that air and the standing water will evaporate fast. Sometimes a tightly sealed greenhouse is not as efficient as one that leaks!

 

[gonewild]

Lance, I find your responses to be very thoughtful and astute - except for the last sentence in your reply to me. <insert grin here> Sorry for taking things wrong.

Ray, I will never intentionally write anything to pick on someone, to easy just to not write anything. But I will sure argue and discuss!

 

[TyroneGenade]

I believe it is due to the high humidity caused by in floor heat evaporating water into the air, and poor air exchange due to the tightly sealed construction done to save heat. Do you think another method of air exchange would be helpful, and if so, any suggestions?

On solution would be to pump cold air (or rather water) through a radiator into the green house which can condense the humidity. There used to be an Atlanta Orchid Society Bulletin PDF online detailing how Alan Reinke used solar heating to heat his green house through winter, by pumping solar heated water through the green house and storing the heat in larger water barrels. This simple heat pump can be used to good effect to pump heat out as well. Instead of running the water through a solar heating array one simply runs it through the cold earth or through steel or copper pipes mounted in the cold air. Pumping water or some or other coolant through the outside pumps and then through a radiator you can dehumidify your air as well as collect lovely distilled water for your orchids.

The efficiency of the system will depend on the surface area available for heat exchange.

 

[Brabantia]

I could not been able to imagine that my initial question would generate as many pages of discuss very interesting in addition.
But maybe the exact direction of my question was not well understood, English is not my native tongue.
I reformulate this one: It is well-known that an excess of nitrogen weakened the plants and makes them more sensitive to the fungal and bacterial diseases (large cells with thin walls). Can the ratio nitrogen / potassium modify this sensitivity to the diseases? As for example: a fertilyser 13/5/20 would it be more appropriate than a fertiliser13/4/15? Of course these fertilizers would be always used with Calcium and Magnesium in sufficiency.
Thank you in advance for your comments which are always very spiked and appreciated.

 

[Ernie]

Can the ratio nitrogen / potassium modify this sensitivity to the diseases? As for example: a fertilyser 13/5/20 would it be more appropriate than a fertiliser13/4/15? Of course these fertilizers would be always used with Calcium and Magnesium in sufficiency.

Good refocus. Like I said, it's really hard to say, and difficult to test satisfactorily to generalize for "all orchids". However, I'd say that the difference between your two examples is nearly negligible and you will see little difference in a hobby collection using a 13-5-20 vs a 13-4-15.

 

[gonewild]

The answer to your question is "Yes", the ratio nitrogen / potassium can modify this sensitivity to the diseases.

You are on the right path with what you are thinking. However the answer is very complex and can not be as simple as a percent formula.

The balance between all of the nutrients (minerals) is important. Not just between one or two. The MSU formula comes the closest to being perfect for a wide range of tropical plants growing in artificial media.

Yes if your Nitrogen level is to high compared to other nutrients the leaves grow fast and soft and become more prone to disease. But there are many factors that can influence the best fertilizer formula to use. Things like does your media hold nutrients or do the nutrients wash out quickly? Is your day and night temperature correct for the species you are growing? Is the light level strong or weak?

The MSU formula was not "invented" for orchids. It simply is a formula that works well because it provides a good ratio of minerals for orchids. The basic formula was being used by commercial growers long before MSU published their studies.

 

[Brian Monk]

The answer to your question is "Yes", the ratio nitrogen / potassium can modify this sensitivity to the diseases.

Nitrogen/Phosphorous/Potassium ratios are also responsible for some aspects of "physiologic timing" in certain orchid species and genera. For example, phosphorous is often proposed as a "bloosom booster" in orchids, especially when applied inthe fall. I think we have all discovered that phosphorous is not as necessary in the quantities previously used in general orchid culture. But the ratio of phosphorous to nitrogen does change seasonally. With Cymbidiums, one can achieve a cessation of the growth phase of a plant, and an initiation of a resting/reproduction phase by increasing the phosphorous:nitrogen ratio for several days. This is a potentially devestating technique, as I have been told by several comercial growers that it can cause even very weak plants to bloom quite well, ensuring a severe decrease in the next years growth and often the death of the plant.

 

[Ross]

What is the humidity of the outside air?
To dry the foliage you have two basic choices... raise the air temperature or lower the humidity of the air.
As odd as it sounds letting in some outside cold air might be cheaper than just running the heaters. If the humidity is lower outside bring in some of that air and the standing water will evaporate fast. Sometimes a tightly sealed greenhouse is not as efficient as one that leaks!

Current temp is 16F