Leaves turning yellow, water issue?

[prismane]

I have been studying this issue I have had with 2 of my phragmipediums and I don't think I am quite getting my watering right. The short story is 2 of my phrags are showing yellowing leaves from the tips. I water with RO Water with a small amount of better gro fertilizer added at each watering. I use 20-14-13 (TDS never higher than 75). On occasion I supplement my water with dilute calcium nitrate and epsom salt (I never let the tds go above about 75). I flush weekly and the flush water shows pretty low on the TDS meter.

I have:
Phrag Green Hornet (Logifolium x Pearcei)-Just finished blooming and is producing 4 new growths (growing fast). All old growths have leaves where the tips are yellowing back. Repotted, showing lots of new root growth but leaves yellowing. In orchiata, large perlite charcoal, moss top dressing with a couple pieces of oyster shell. Watered about every other day. Always kept wet.

Phrag Jason Fisher-Seedling size. Growing quickly. In straight Orchiata. Watered every other day and always kept wet. Not showing any problems with the water I am using


Phrag Court Jester. Recently acquired, repotted into fresh orchiata, perlite and charcoal. Tip is turning yellow. Roots not strong.

Light: Window supplemented with LED. Cattleyas have grown and flowered under this setup.

 

[Ray]

"Never over 75 ppm TDS" really doesn't tell us a damned thing about the actual amounts of N, P, & K, Ca, or Mg that you're applying, but I'd bet that some of what you're seeing is an insufficiency in the last two, if not nutrients altogether.

A customer recently measured the TDS of 100 ppm N K-Lite at around 500 ppm, so if I ignore differences between meters, their general inaccuracy, and ratio the concentrations of the ions, you're probably applying less that 15 ppm N, which, by itself, isn't all that bad.

Calcium, however, is needed constantly by a growing plant, as the mineral is not well translocated within plant tissues, so your occasional application is a concern.

I have no idea what TDS it produces, but a teaspoon of Epsom Salts per gallon will provide plenty of magnesium with no stress to the plants.

 

[prismane]

"Never over 75 ppm TDS" really doesn't tell us a damned thing about the actual amounts of N, P, & K, Ca, or Mg that you're applying, but I'd bet that some of what you're seeing is an insufficiency in the last two, if not nutrients altogether.

A customer recently measured the TDS of 100 ppm N K-Lite at around 500 ppm, so if I ignore differences between meters, their general inaccuracy, and ratio the concentrations of the ions, you're probably applying less that 15 ppm N, which, by itself, isn't all that bad.

Calcium, however, is needed constantly by a growing plant, as the mineral is not well translocated within plant tissues, so your occasional application is a concern.

I have no idea what TDS it produces, but a teaspoon of Epsom Salts per gallon will provide plenty of magnesium with no stress to the plants.

Where did you get these nutrient values that you are targeting for phragmipediums? Can you give me reference?

 

[abax]

I grow a lot of Phrags. and I recommend K-Lite once a month in winter and
every 7-10 days in summer at 1/4 tsp. per gallon. How's your humidity in
your growing area? My personal experience in my greenhouse is less watering and higher humidity with LOTS of air movement. Some Phrags develop brown
leaf tips on old growth and some never do in the same conditions. I donno
why!

 

[Ray]

Where did you get these nutrient values that you are targeting for phragmipediums? Can you give me reference?

The original concept for the applied concentration was derived from Benzing's Vascular Epiphytes, in which the measured concentrations of nutrients (almost all nitrogen) in the water cascading though the forest canopies in the tropics tended to run in the 15-25 ppm TDS range, and happened at least daily.

While slippers may not really be epiphytes, they tend to live on substrates that are very nutrient depleted, or at least that's my rationale, as I treat all of my orchids equally...

Beyond that, it's based upon about 6 years of experience, in which I've been applying K-Lite (12-1-1-10Ca-3Mg) at 25 ppm N every 2-3 days, with KelpMax and Inocucor Garden Solution each, applied once per month.

Angela's recommendation of 1/4 teaspoon/gallon K-Lite is about 35-40 ppm N, by the way.

 

[xiphius]

If you are keeping them very wet and flushing weekly, then you are probably not giving them enough nutrients.

I was a little paranoid when I first got my besseae and ended up doing something similar. Increasing the ferts a bit greened it back up. If you are diligent about keeping your phrags very wet, then I have found that it is not as critical to worry about keeping your TDS super low. My regular water and fert solution is above 100 ppm (total) on the TDS meter and I have no issues even with besseae and andreettae (which both have a reputation for being finicky). Normally I shoot for around 30 ppm N with MSU RO fertilizer (Rays recommendation) and then add some kelp extract and Superthrive. I flush with my tap water (from a well) that is around 120 ppm TDS. If they are growing at a decent rate, then phrags can take more ferts then most people give them credit for.

That said, I wouldn't take tap water that is baseline 200+ pm TDS, add ferts on top of it, and expect plants to thrive .

 

[prismane]

I grow a lot of Phrags. and I recommend K-Lite once a month in winter and
every 7-10 days in summer at 1/4 tsp. per gallon. How's your humidity in
your growing area? My personal experience in my greenhouse is less watering and higher humidity with LOTS of air movement. Some Phrags develop brown
leaf tips on old growth and some never do in the same conditions. I donno
why!

I grow my phrags in a room in my house. Right now it gets about 65 at night and about 75 during the day. I run a humidifier and a fan and the humidity never dips below 50% but maxes out at about 60%. The rest of the house it dips pretty low.

I have read about K-Lite fertilizer in the AOS journal where they seemed to be under impression that a lot of our fertilizers way overkill with potassium and this problem is compounded with low calcium and magnesium. I have thought switching to something like K lite.

 

[prismane]

The original concept for the applied concentration was derived from Benzing's Vascular Epiphytes, in which the measured concentrations of nutrients (almost all nitrogen) in the water cascading though the forest canopies in the tropics tended to run in the 15-25 ppm TDS range, and happened at least daily.

While slippers may not really be epiphytes, they tend to live on substrates that are very nutrient depleted, or at least that's my rationale, as I treat all of my orchids equally...

Beyond that, it's based upon about 6 years of experience, in which I've been applying K-Lite (12-1-1-10Ca-3Mg) at 25 ppm N every 2-3 days, with KelpMax and Inocucor Garden Solution each, applied once per month.

Angela's recommendation of 1/4 teaspoon/gallon K-Lite is about 35-40 ppm N, by the way.

Thanks for the recommendations. I am a little unfamiliar with using US measurements. I plan on getting a balance to start weighing out my fertilizer to get a better idea about how much I am adding and then dilute it into a 5 liter container. Are you factoring in the percent composition by mass from the chemical formula for each nutrient into these calculation or are you going simply off the 12-1-1-10-3 numbers?

 

[Ray]

As nitrogen is THE most important nutrient, professional growers generally control their feeding regimens by controlling the nitrogen, while using a formula they have chosen to provide the rest of the nutrients in amounts they're happy with.

On a fertilizer label, the nitrogen is expressed in elemental weight percent, so that makes it relatively easy to calculate concentrations, especially using the metric system. A part-per-million (ppm) is equivalent to a milligram-per-kilogram, so if you're looking for 5 liters of a 25 ppm N solution using a 12%N fertilizer, you need to mix 5kg x (25mg/kg / 0.12) = 1042 mg, so a simple 1g of fertilizer per 5L would be fine, giving you 24 ppm N.