Are my Vandas getting enough light?

[rving87]

I got my first orchid, a NOID dendrobium mid June this year. 70 days later, I have 70 different varieties (species+hybrids). I know the popular advice is to go slow, but a) They're fascinating! b) They grow like weeds in my climate (Mumbai, coastal India)

Rushing into it, I've made some mistakes, but orchids are so forgiving in many ways that they bounced back (my first batch of 5-6 mistakes. Been smooth sailing since then)

The grow area is my terrace, but with a opaque shade at about 12 ft height. So it very much acts as a very bright room rather than an open air netted /greenhouse facility. All my orchids are placed on the terrace walls. The terrace is open on three sides -East, West and North (Blocked by adjacent building at about 10 ft away). South is the entrance to my terrace.

All my Vandas are at the east facing window. They have great growth with scores of root tip growths, and leaf growth as well.

I would've been sleeping peacefully if I had not gotten a lux meter. On clear mornings, (this is peak monsoon season, so it is still slightly cloudy on the occasional clear morning, could improve next month) the east facing plants get upto 55-60000 lux (average 20000) for 4 hours. Then their light levels drop to 12-15000 lux for the next 5 hours. The next 3 hours is relatively weaker light from West, maxing at 30000 lux.

I am not worried about any other orchid other than my Vandas. Although they're growing, I would like to ensure they flower as well. Lot of fuss has been made about Vanda lighting in tutorials and on YouTube. I sometimes convince myself that if people are able to bloom this in colder and more northern climates, then I shouldn't have a problem. But then I remember the lux meter readings and start calculating my estimated dli to compare with the dli of the area in which the guy in the youtube video lives. But I still do not know what he would mean by partial shade, or my eastern wall. Because my meter shows me that the orientation of my plant relative to the overhanging roof can mean a difference of 40000 lux for an hour.

Has anyone taken actual readings? Scouring the internet, I could find readings at best from commercial growers. Home growers? With blooming Vandas?

[Roberta]

First, Welcome!

Don't overthink the light bit. Orchids are really adaptable. It sounds like they are doing very well in terms of groiwing - new roots are a great sign. If you find, over time (like a year or so) that you are getting growth and no blooming, you can supplement the natural light with LEDs or fluorescents. Longer duration (especially in winter if you are in the northern part of India) can compensate for intensity. (The farther south, the less seasonal day length is an issue) But at this point, orchids teach patience... nothing happens fast.

[rving87]

Thanks for the words of encouragement Roberta! Taking your advice and leaving them alone for now.

[estación seca]

Welcome to the Orchid Board!

[Veena Manohar]

Hi rving87! I too have a similar growing area with a poly carbonate sheet over half my balcony. My lux readings are pretty low ( 4000 - 6000 max)because it’s been overcast for two months straight. So I’m waiting for the end of the rainy season. I suffered from a similar situation. No blooms!😖
I fertilized weekly with the normal 20:20:20 ( three big pinches) and always added Rexolin Chelated Calcium ( three small pinches) and 5 ml of symbion nitrogen fixer. All to a three liter sprayer. And a pure spray of Epsom salts once a month.
Then we went to buy orchids at a nursery for my bday and I spoke to the owner about my non blooming yet leaf and root bounty problem. He advised me to use 0:52:34 weekly for two months because he thought I was Going too heavy with the Nitrogen. He asked me to use my normal regimen on plants that had just finished blooming( none &#129320.
In two weeks I had spikes on my Vanda, oncidium, Cattleya and my Dendrobiums. 🤗
First in a year. LUX was abysmal.
Needless to say I’m over the moon.
Hope this was useful.

[rving87]

Hi Veena! Thanks for the info, it gave me some much needed confidence. I'm assuming from your info that you're growing in Pune, so the weather is similar as well. This input was therefore very valuable.

Fertilizer wise, I read through a lot ( really, a LOT) of studies, papers and they all pointed to what you say - that high N induces vegetative growth and delays reproductive growth in orchids. I decided to take a different approach, which is the MSU formula, but even more dilute, at 25ppm N, what Ray recommends lately

A Regimen for Growing Excellent Plants >> First Rays LLC

He does use a low potassium mix, but I made a batch of about 200g of MSU fertilizer from raw ingredients sourced from Amazon. For 4.5 L (my average daily use of water - I spray until it runs down the pot) I mix 1.5 g of my mix with <5ppm RO water to get to 25ppm N. At this rate I have 3 months of fertilizer supply left, so maybe I'll mix my next batch with Ray's K lite ratio.

So my fertilizing is every day, but at miniscule doses. Apart from this, I have used Vamoz Mycorrhiza and Utkarsh Microbes once a month for biological nutrient availability.

Like I mentioned above, I've been in this for just two months, maybe another 4 -5 months down the line of I see no spike, I might withhold fertilizer altogether for a couple of weeks, and see if the nitrogen withdrawal induces flowering.

Thanks again for your inputs, they were very useful insights!

[estación seca]

Welcome to the Orchid Board, Veena!

Vandas tend to be seasonal rather than flowering through the year. Many hybrids flower in late fall-winter-early spring.

Especially in a hot climate, Vandas can use a lot more fertilizer than other orchids. More nitrogen leads to more spikes, and withholding nitrogen leads to poor flowering. The authority I quoted before, Martin Motes, is in very southern Florida. It has a climate resembling a summer monsoon, but with some rain in winter. He writes that he waters his Vandas at least once a day, year round, twice in hot weather. He fertilizes every 5th watering with almost 1,000 ppm nitrogen, which is 15ml of 20-20-20 powder in a US gallon, 3.78 liters. This is far more than recommended for most other orchids. He writes that seedlings can use even more than this for proper growth. A properly fertilized Vanda will have a light green zone at the base of the currently emerging leaf that is about 1cm wide. If the zone is narrower, the plant needs more nitrogen. If it is wider, the plant needs less nitrogen. Motes writes that poor flowering is caused by insufficient fertilizer or inadequate light. Since I began using the much higher doses and paying attention to the light green zone at the base of the leaves, my seedlings are growing much better.

Find out what minerals are in your city water. You may have enough calcium already, and you would only need to adjust the pH to 5.5-6.5 to make the calcium more available. Your water utility may publish a water report.

Vandas do seem to need more magnesium than other orchids. Deficiency shows up as tiny red marks during cool weather. It can take months of supplementation to replenish the plant's magnesium.

[rving87]

Hi Estacion!

I did watch some of Mr Motes' videos earlier, although I don't have his book. He says he follows the MSU regime, shifted from his earlier fertilizing practice, about 18 minutes into the video below.


*rough cut* Florida Orchid Growing Part 2: Florida Vanda Growing - YouTube

[estación seca]

He says he switched formulation from 20-20-20 to MSU, but he doesn't say he switched fertilizing practice. In the video he doesn't discuss how he mixes fertilizer nor the frequency he applies it. I watched that video several times when it came out to see if he would talk about how much, and how often, but he doesn't. And note his water in Florida is very high in phosphorus, so using a low phosphorus fertilizer makes sense.

I don't have a link to the original papers, but you can probably find them somewhere online. Michigan State University did not do any experiments with fertilizer. They just switched their collection to a different formulation. They thought it looked better so they reported what they'd done. The orchid world followed.

I think for most orchid growers, who have less-than-ideal conditions, fertilization doesn't matter in the least. Nutrients are not the limiting factor in orchid growth when it's substantially too cool, or there isn't really good enough light, or it's not humid enough, or the growing season is too short because winter is too long. This is the situation for most orchid growers in North America, Australia and Europe more than about 30 degrees from the Equator, especially those growing on windowsills. But when growers can easily provide correct conditions, fertilizer becomes the limiting factor in growth.

I have heard multiple growers of Cattleya seedlings say they use relatively high amounts of nitrogen at every watering during warm weather, 100-125 parts per million. They only water without fertilizer, to flush salts, once a month. I observed when I upped my fertilizing to this level my Cattleya seedlings began breaking multiple leads at every growth cycle. However, I have warm temperatures, good humidity in my growing area, bright cloudless skies for most of the year and a very long warm season.

I'm not arguing to give large amounts of fertilizer to all orchids. Many can't handle it, and many don't need it. But Vandas most definitely respond to higher amounts of nitrogen when they're grown warm, as in your conditions.

And pay attention to the pH. This does make a big difference in availiblity of other nutrients.

I'm adding that Dendrobiums, mentioned in this thread earlier, do not need much fertilizer. They do best with some extra nitrogen around the time they are beginning new growths, and then they need very little. The nobile hybrids often don't flower if they get any nitrogen past midsummer.

[Veena Manohar]

Thanks estac’ion seca! I guess I must buy a ph meter. I made an interesting observation over our unbearably hot and dry summer ( 26C low and 43C highOn bad days in May. Lasts April to June). As the humidity was 30% on an average I was watering my orchids everyday and my Vandas two to three times a day. I grow them bareroot. They grew roots everywhere and were a happy lot. Ever since our monsoon season began I reduced the watering. As we have 85% humidity on an average. And The roots aren’t growing as well as the summertime. Their Growth tips have reduced too. Otherwise they look ok. And, I checked their New leaves. The light green zone is two millimeters. So I guess I have some thinking to do. That was a great tip estac’ion! Many thanks.
And yes all the Moates videos are interesting!