To fertilize or not to fertilize orchids ?

[Roberta]

Elemental nitrogen in the air (N2) isn't available to plants. (Legumes such as beans have nodules containing bacteria that can "fix" the nitrogen from the air into bio-available forms, don't think orchids can.) But in a lot of locations, there are nitrates, nitrites (NOx) in the air. It's pollution, but certainly could do a bit of fertilizing (a very little bit)

[Orchid Whisperer]

Roberta:

The environmental calculations I mentioned are in the State of Georgia's GUIDELINES FOR SLOW-RATE
LAND TREATMENT OF WASTEWATER VIA SPRAY
IRRIGATION. (sorry for the caps, I just cut & pasted the title). The 5 lb N /acre/year value is correct. I suspect this constant is based on EPA research, but I would need to research it further to be sure. Although I do different work now, about 23 years of my career in environmental work included nitrogen budget calculations.

I agree that the N2 in the atmosphere is the dominant N form, and is not available to most biological processes, unless it is fixed by N fixing bacteria. If atmospheric N2 was more readily plant-available, we would probably never need N fertilizers.

There are other sources and forms of atmospheric N. Decomposition processes on the ground do volatilize a substantial quantity of N. Lighting also converts some N2 to NO3-. Oceans store and volatilize substantial N to the atmosphere. Just some examples.

[Cymbaline]

Originally Posted by SouthPark

Definitely - claims of never fertilising is one thing. But adequate details (from them) would be required. This includes growing media, growing conditions (where the plant is placed or mounted or potted), and what sort of water they use, and water-analysis results (details). Also - details about what they find or see inside the pots (after a long time of growing).

For growers that sometimes re-pot orchids (upgrading to larger pot etc), some may find cases of insects/organisms living in the pot, or some sorts of harmless fungi growth etc. Some factors may allow the orchids to acquire the 'nutrients' that they need without 'manual fertilisation'.

You are right. I should have added to my post that this is the Water Culture Orchids & General Orchid Care group in Facebook and the two people who keep making these claims keep their orchids in water culture. I think the full water culture ( as they call it ).

I have been in the group since 2018 trying to learn about orchid care and these two are very active in the group so I remember things they have said in the past.

One of the ladies, has mentioned before has well water that is softened with potassium and uses that to water her orchids. I have a potassium water softener as well and from what I understand , not all potassium is removed from the water in the water softening cycle. So it's my though that her orchids are at least receiving potassium in their water so there is that.

---------- Post added at 07:17 AM ---------- Previous post was at 07:06 AM ----------

Originally Posted by Ray

Yeah, I've heard the "my grandmother never feeds her plants.." line many times.

Once or twice it was followed up with "Manure tea isn't food, is it?"

I received my very first orchids via. inheritance from my aunt . The orchids are for sure 10+ years old as I remember them being in different houses. Her house then later her nursing care home (retirement home?),.

Anyways I can attest that these two were pretty neglected and thankfully they survived but didn't really thrive. They never grew new pbulbs or bloomed. Just lived. They also were different types of orchids growing in the same pot. A dendrobium and an oncidium.

So for 10+ years they were in the same medium, in dim light ( east window of her bathroom ) and only occasionally watered.


Once I got them in the end of 2017 to mid 2018 they did a little better . The oncidium grew new pbulbs but they didn't fatten up. I think because I had them outside on my patio where they got better light.

In 2018 , I started to research what to do with them . Repotted , and took them indoors and placed a grow light over them and also started fertilizing / watering weekly and suddenly they took off. The Oncidium's pbulb fattened up very nicely but no spike. It rapidly started new pbulbs however. The dendrobium grew a HUGE pbulb.

So I take it that either the extra light or the extra fertilizing or both was appreciated .

[Roberta]

Originally Posted by Cymbaline

I have a potassium water softener as well and from what I understand , not all potassium is removed from the water in the water softening cycle.

A potassium water softener uses potassium instead of sodium to replace the hard-water calcium, so it doesn't take any potassium out, puts an amount in to replace the calcium. Much more potassium than plants need, but much less harmful than sodium (a big no-no for plants). So that is the benefit of this type. The calcium in the original water is not harmful at all to the plants. Actually, the potassium-softened water is higher in Total Dissolved Solids than the original "hard" water (do the chemistry replacing calcium with potassium) Still, you can get away with it (but probably better to use the untreated water)

[Cymbaline]

Originally Posted by Roberta

A potassium water softener uses potassium instead of sodium to replace the hard-water calcium, so it doesn't take any potassium out, puts an amount in to replace the calcium. Much more potassium than plants need, but much less harmful than sodium (a big no-no for plants). So that is the benefit of this type. The calcium in the original water is not harmful at all to the plants. Actually, the potassium-softened water is higher in Total Dissolved Solids than the original "hard" water (do the chemistry replacing calcium with potassium) Still, you can get away with it (but probably better to use the untreated water)

Okay good to know. I have a RO for my carnivorous plants which can't take high TDS , I'll start using it for my orchids.


Thank you

[ArronOB]

This question has been bothering me too.

I was an enthusiastic grower of mainly Oncidium and cattleya type orchids from about 1996 to about 2008 when life intruded. I fertilised once every year or two during that period, which I thought well mimicked the conditions of the various epiphytic species growing naturally in the area. This was not slow realease fertiliser.

From that point till about 3 years ago I had a residual collection of hardier species growing at our holiday home which I never fertilised.

Then about 3 years ago we moved to a location with slightly milder winter weather and my interest was rekindled, with now about 150 mainly Oncidium and cattleya types. I now fertilise weekly and apply kelp monthly.

I don’t believe there was any difference in growth or flowering between the early period and now. Maybe there is, as it was 20 years ago and memory plays tricks, but I just don’t think so.

I am, however, doing my bit to keep the fertiliser companies rich.

So why do I fertilise so regularly. I think it’s some type of FOMO. Maybe, just maybe, it makes a little bit of difference and I can’t bear to forgo that possibility.

I think the internet plays a role. In those early years there was no equivalent to this type of forum so there was less connectedness. Less circulation of ideas good and bad, less envy of other people’s plants, less marketing and hype over nonsense products, no thought of purchasing products out-of-area.

Through all this time I have grown in bark which I make sure is well aged before I put plants in. Water with our very good municipal supply. My plants grow outside, mainly in shade houses. I don’t get too particular about ‘cleanliness’.

My conclusion is that orchids need only a minute amount of fertiliser. Ninety-something percent of what we give them is wasted. I’m the worst culprit.

[Ray]

Originally Posted by ArronOB

My conclusion is that orchids need only a minute amount of fertiliser. Ninety-something percent of what we give them is wasted.

I am quite in agreement.

It is very well established that poinsettias must have 1/2 gram of nitrogen to take them from a rooted cutting to their fill Christmas glory. Growers know - and I do mean "know" - the 1) volume of their pots, and 2) the water-holding capacity of their potting medium, which allows them to know the holding capacity of each pot. They also know the time until harvest and the frequency of feeding, so they can closely calculate the concentration of fertilizer they need to apply at each watering, so the net over the time period is 0.5g N/pot.

Switch to orchids...

We can certainly calculate the volume of a pot, but unlike poinsettias, we do not know the water-holding capacity of the medium, and cannot trust that the roots (being far less extensive than those of a terrestrial plant) absorb all - or even a large percentage - of the absorbed solution. Plus, as they are - relative to most terrestrial plants - very slow growing, we may not have a guess at how much fertilizer they need in the first place.

OF COURSE we're wasting most of what we apply.
However, we can still make adjustments that move in the right direction.

My personal regimen involves frequent watering with very dilute fertilizer, which is what makes the ions available for absorption and wets the velamen so they can be. I use KelpMax regularly, so my plants have more extensive root systems than they used to, so seemingly have a greater absorption capacity. That is further improved by my use of Inocucor, which, by populating the plant and medium with a beneficial fungal network, increases the absorption capability exponentially (a bit of hyperbole there, as I don't really have a number) via the hyphae network.

[DirtyCoconuts]

I had no idea rainwater could be so dirty!!!