To Fertilize or Not?
 

[MODERATOR NOTE: Following is a discussion moved from a different thread by me (WaterWitchin) which may be of interest to those beginning their orchid journey]

All mine [Sarcochilus] also outdoors on a NNE facing balcony but with nothing to shade except building structure on the south and east sides. Temps here usually about 10 degrees warmer than SF.

Seen a couple of leaves yellow but seems it’s because there's new growth elsewhere, roots or new fan/leaf, so I think nutrients are just being recycled elsewhere. They definitely grow much slower than Phals.

Plain tap water daily since April. No fertilizer.

What is your reason not to fertilize?

I don’t think they are heavy feeders but I think they certainly will benefit from it. They need their “vitamins” to grow, just like we do.

IMHO, in the end you’ll notice deficiencies.

Nothing other than just being a complete newbie to growing anything other than Phals.

Read many posts that most important is to get cultural conditions right because if they aren't, fertilizing won't help. I agree from personal experience with a couple of my Phals. Since I killed an Oncidium from dehydration, I wasn't even sure I could provide conditions well enough for any of the plants I got last Aug/Sept to survive, let alone flower. Kinda wanted to see how they did for a full year before changing anything up.

A couple have been pooped on by birds. Sometimes gets pretty windy so also had a little leaf litter buildup (read that's where some Sarcs are found in the wild growing on rocks around streams) and some minerals in plain tap water (calcium?) was my rationale that they might still be getting a teeny bit of "natural" fertilizer. But I did buy a general 8-8-8 fertilizer to start trying later this year if any seemed to do well enough.

Orchids are slow growers and it will take a while before deficiencies show up. A year is nothing in an orchids life.

Certainly getting cultural conditions "right" is the most important part. I don't agree with "fertilizer won't help." Yes, as you have discovered, fertilizer won't help if your plant is so dehydrated it can't survive. Neither will it assist with any excess lack of culture with rotting medium, too much light, too little light, temperature that is too cold or too hot for the particular plant, Bird poop and leaf litter buildup aren't particularly important either way unless excessive. Using tap water works for most orchids other than if high TDS you're going to fight mineral buildup.

Fertilizer won't cure cultural conditions that are going to kill the plant in the long run anyway. What fertilizer CAN help with is giving the plant more vigor to survive cultural mistakes while you're tweaking what the plant needs in the way of correct watering, temperature, air, and light.

I use a 12-1-1 10 Cal-3Mag fertilizer with RO water. You don't need to get that carried away, but there's also a reason there's a different NPK for different plants...for example I don't use a fertilizer formulated for tomatoes on my violets or vice-versa.

It can't hurt to use fertilizer, and probably might help. You might want to give them a boost while you're learning the culture. Fertilizer is much cheaper than orchids.

Orchids (and many other plants) in habitat have fungi growing inside through outside their roots. These fungi help the plant absorb nutrients from the surroundings. Orchids grown in labs lack these fungi. Fertilizing is necessary for our orchids.

Many people never fertilize house plants, then they wonder why their plants die. House plant potting mixes contain no nutrients beyond a few the manufacturer may put in the bag. Once these are exhausted the plant has no nutrition. I ask these people whether it would be reasonable to keep a house cat and give it nothing but water and a litter box?

Well, the housecat would show the ill effects much sooner... green plants do take care of the basics - carbs - thorough photosynthesis. Cats need the carbs to live. But eventually, the plants also need to grow new tissue, and that's where the "vitamins" come in . To some extend they can "recycle" tissue from old leaves, spikes, etc. to take even longer to show the effect of not getting the minerals. But eventually it does catch up with them. To thrive (not just survive) they do need a bit of fertilizer. Not much, but they do need some.

Is it possible orchids grown outdoors can pick up mycorrhizal fungi up through airborne spores or decomposing leaf litter? I compost a little on my balcony for my few non-orchid plants.

We don't have the mycorrhizae in our environment that orchid seeds need to germinate... that is why they have to be propagated in flasks with media that provide the necessary nutrients. I would not consider whatever they may pick up from the environment to be a source of nutrition, at least not a reliable one.

I don't know whether just a few fungi coexist with many orchid species, or whether it's a nearly one-to-one species to species cohabitation. Almost all species of orchid need symbiotic fungi in habitat for seeds to survive. The fact that almost no orchid seeds will germinate in cultivation without laboratory intervention tells me the symbiotic fungi do not set up housekeeping with our orchids outside habitat.

The bottom line is a small amount of fertilizer is necessary for orchid growing. Plants we buy come from sellers who probably fertilized heavily to get them to market size as fast as possible. In our care there may be sufficient nutrients stored for some time, perhaps up to a year or more. But once the stored nutrients are gone, the plant will suffer.

Calcium and magnesium may come from most tap water, but other nutrients don't. Nitrogen is always important for plant growth. Plants can't synthesize structural nor enzymatic proteins, chlorophyll, nor nucleic acids for cell division and growth, without an external source of nitrogen.

Edit: At the lecture I heard, Mr. Barrie from Australia said they water their Sarcos at the nursery with fertilizer solution 365 days out of the year.