Feeding Vanda Orachoon x Vanda tessellata
 

I was gifted this plant by a member of my local orchid society—thanks Jim! Luckily, I have the space to accept things like this, but my experience with vandaceous types has been limited to small seedlings.

Since I’ve had it I’ve been spraying the roots till the point of runoff twice a day with the same 25PPM nitrate solution my mounted plants get, but I feel like that’s not what it wants—it seems like everyone is feeding their Vandas quite heavily.

I mix up a 100PPM nitrate solution from concentrated stock everyday for my solitary mounted Catasetum; would this Vanda appreciate the same amount of feed as the Catasetum and does being in bloom change how I’d feed it?

Thanks in advance for any and all input/criticism!

Some photos…You can click on them for a closer look

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https://i.postimg.cc/hfbwZzg3/IMG-1536.jpg

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I leave it to others to tell what is best for the Vanda - I tend to 'way under-fertilize. Blooming makes no difference in the regimen. But it seems to me it is pretty late in the season for that much fertilizer for a Catasetum... those should be slowing down now - with reduced or no fertilizer. You might want to start a separate discussion on that one, in the Catasetum forum.

Thanks you Roberta! I’m sure it appreciates whatever water it can get while it’s getting used to its new surroundings—I just want to do everything I can to keep this blooming for as long as I can.

Will be posting in Catasetums shortly!

All plants need the same amount of fertilizer and water to add the same amount of mass - for one pound of tissue to be generated, it requires about 5 grams of NPK (essentially all nitrogen) and about 200 pounds of water. Add to that the fact that plants lose upward of 95% of absorbed water to transpiration, and that latter becomes 2 tons of water.

I think the "heavy feeder" reputation of vandas is simply due to the fact that they have "instantaneous uptake" only, when the velamen is wetted, as they are so-often grown bare root and do not have the "extended absorption period" that a plant potted in a retentive medium may have.

Please clarify your fertilizer solution parameters. You referred to 100 ppm and 25 ppm, but is that ppm TDS or ppm N? The latter is the important measure, and they can be significantly different. The original MSU WW formula, for example, has a TDS that is 5.3x the ppm N, while the TDS of the RO formula is 7.4x the ppm N.

Also, how are you determining the concentration? weighing, EC measurement, or TDS meter?

If you want to apply some serious SWAG (scientific wild-assed guessing) to the question, you can estimate the nutrient uptake with this calculator, but you need to estimate the total length of the roots on that thing, their average diameter and velamen thickness.

For example, of those are about 175 cm in total length, their average diameter is 5 mm, and the velamen thickness is 1 mm, then when using a 100 ppm N solution, the maximum uptake per watering is only 2.2 mg N. That would suggest that you need to provide 5000/2.2=2273 feedings for the plant to grow a pound of mass. (~6 years if you do that daily)

Howdy Ray; I am most pleased that you’ve decided to participate!

On the topic of the ‘heavy feeder’ reputation of vandas growing bare root, the absence of any media to retain moisture and nutrients makes total sense. I suppose everybody is just different in how they feed: I’ve dug through the vanda threads that talk about feeding and it seems like it’s a case of ‘ask 10 growers’—some praised the Motes method(1TBSP of 20-20-20 per gallon of water every 5th watering) while others called it a waste, and everything from pantyhose to algae extract in between. That being said, I can’t find anything wrong with starting out low and slow and working up to higher fertilizer concentrations just to see what works well for my conditions.

On the topic of my fertilizer parameters, I apologize for my lack of clarification—all of my numbers are PPM of nitrogen. I tend to write ‘nitrate’ after the concentration to sort of differentiate between TDS while simultaneously letting people know what kind of N I’m talking about; I’ll work on that! I weigh(pocket scale) all of my materials and will use a TDS/EC truncheon to check for consistency from time to time—2.4g of calcium-ammonium nitrate decahydrate (15.5-0-0)per gallon of my tap water(~100PPM TDS) yields a solution at ~400PPM TDS, of which ~100PPM is supposed to be nitrogen in the form of nitrate. That was just an example for the nitrate—I add maybe .4g of other mostly non-nitrogenous stuff(.3g magnesium sulfate heptahydrate and .1g of Masterblend 4-18-38) to sort of round it out and add some micros. This is my stock solution that’ll get diluted for everything besides the Catasetums and maybe the Vanda.

Now the topic of SWAG has me flooored: I was having a spirited conversation with someone close to me about how one could theoretically calculate nutrient uptake using the volume of velamen and this person laughed in my face…Somebody’s eating crow for dinner and I cannot wait to show them the calculator! Thank you for sharing that with me—I know there’s a storm coming my way and there are probably more important things to do, but I do have a pair of calipers…

Thanks again for stopping by, Ray!

Whoa, Nellie!!! You’re putting a lot of faith in SWAGging!

One of the big unknowns is how quickly nutrients move from the velamen to the vasculum and beyond, and that can have a significant impact on the guesswork.

I dont know about others, but here is my Vandas after all the last few months after I bought them at Lowes,they only have recieved the local well water(thats all)
Attachment 168530
Sorry its so blurry
This is the same v. as next to my name but its a new spike and blooms.

Whoah there, SWAGging qualifies as a deliberate and educated guess or whatever fits the current narrative around these parts(I’m looking at big sugar, Army Corps of Engineers, EAA reservoir, and the SFLWMD)!

I don’t get many ‘I-told-you-so’ moments, so I have to seize this one!

On the topic of how quickly the nutrients move through the plant, I wonder if that could be quantified by taking tissue samples at different times before and after heavy feeding. Maybe put the plant on a fasting diet of just water, take some root and leaf samples for reference after the fast but before the feed, then feed it a ton and take more root and leaf samples from different parts over a period of time and compare it to the ‘fasting’ numbers…I’m not going to do this, but a man can dream!

---------- Post added at 10:45 AM ---------- Previous post was at 10:39 AM ----------

Heck if you’re pulling it off on just well water, I am very likely overthinking it…Hopefully my plant won’t mind this weeklong spell of dim light and wind. How often are you watering WD?

WD, be a little careful about drawing conclusions after just a few months. If it is still that happy after two years of just well water, then you may be able to draw some conclusions but in the short term, it may be still be drawing on reserves from its previous life in a nursery.

I saw a video of a lecture on the subject, and they used the N15 isotope to track movement in Phal. Sogo Yukidian plants. In a nutshell, after a single dose of fertilizer solution, they noted a small increase in the N15 concentration in all tissues after one week, and it pretty much leveled out between 8 and 16 weeks after application.

They applied a nutrient solution containing 11.25 atomic% N15, and a week later only about 1/10 of that was detected in the plant itself.