Rhynchostylis gigantea - chlorosis and dark spots

[vondaix]

Greetings everyone,

Hope you are all well.

I just wanted to see if I could possibly confirm if my rhy. Gigantea has some kind of virus and what to do next if it is confirmed through visual cues.

I got this specimen from an orchid show back in March and I water weakly with a balanced fertilizer, seaweed, and Epsom salt. I spray with calcium about once a month. Watering is done 2-4 times in a day depending how hot it is. It gets about 2 hours of direct morning light until 10AM and then is shaded for the rest of the day.

I have other orchids as well and do not want to spread it around.

Your inputs are much appreciated.

[Ray]

In my experience, those dark spots are common and nothing to be concerned about. The yellowing of the lower leaves is due to the plant drawing the stored water and nutrient reserves out of them.

Can you please provide details about your feeding regimen and how you are watering and applying them?

[vondaix]

Thank you for the quick reply!

To be honest, I'm not so worried about the dark spots but more so on the "ringspot" looking ones under the side of the leaves.

I have a 2 gallon pump that I put 1/2 tsp of balanced fertilizer in, 1 tsp seaweed, and 1 tsp epsom salt. I water this rhy. gigantea alongside my other vandas until they are soaking wet, the white parts of the new root growth turns green, about 2 minutes of a strong spray each basket (not mist).

Let me know if there is room for improvements for my watering regimen. I also know a hose would be most effective but I live on a second floor of a triplex so it's not accessible.

Thank you again.

[Ray]

Originally Posted by vondaix

I have a 2 gallon pump that I put 1/2 tsp of balanced fertilizer in, 1 tsp seaweed, and 1 tsp epsom salt.

That information is of very little value unless you share the formula of the fertilizer and the seaweed, and how often you apply them.

20-20-20 and 1-1-1 are both balanced fertilizers, but 1/4 tsp/gal of the former is about 10 ppm N, which would be sufficient if you applied it daily, while that same amount of the 1-1-1 would be essentially no feeding whatsoever.

How about the seaweed extract?

Do you even need to supplement magnesium? What is your water supply?

[vondaix]

Originally Posted by Ray

That information is of very little value unless you share the formula of the fertilizer and the seaweed, and how often you apply them.

20-20-20 and 1-1-1 are both balanced fertilizers, but 1/4 tsp/gal of the former is about 10 ppm N, which would be sufficient if you applied it daily, while that same amount of the 1-1-1 would be essentially no feeding whatsoever.

How about the seaweed extract?

Do you even need to supplement magnesium? What is your water supply?

My apologies, yes, I use the 20-20-20 fertilizer. I use tap water and looked up the water analysis for the minerals available. I can't remember the exact numbers but there's barely enough Ca/ppm and not enough Mg/ppm.

That's why I don't add calcium per watering and only do it once per month to top up what's already in the tap water and I add Mg in the solution per watering.

I also spray algaecide once per month for some form of prevention. It has one of the ingredients of Physan20 which is not available in Canada.

[estación seca]

Don't use prophylactic sprays. They can damage your plant. They kill off beneficial organisms. They select for resistant harmful organisms. Algae aren't harmful to other plants.