Fertilizer??! So what is the deal on how to use it?
 

So I'm back with yet another question. So what is the deal with fertilizing my orchids? Most sites I've read said Never give a dry plant fertilizer, so I water them first then fertilize, 1/2 strength, twice a month. I know my Paphs can be sensitive so I only feed them once a month, but no matter which plant I always water it first. Now I have read one site that says just the opposite, "don't water them on the week you fertilize" ????? I'm so confused!!! Please help. Thank You

OK, you will get a dozen different replies to this, so think carefully.

I base my treatment of orchids on what I consider they would get in nature. OK, in places you have to compromise a bit, but watering and fertiliser shouldn't need to be compromised at all.

Go to First Ray's page and read everything he has posted on fertilising. It is a seriously good read. To summarise, he tested what was running down the trees, and went from there.

He has come up with his own fertiliser, K Lite. I consider his theories as very sound. So I use an ultra low dose of his KLite (about a gram in 6 litres of RO water.)
I use this on all orchids, everytime that I water. RO water because then I know exactly what is in it.

If you water and then feed, the fertiliser is wasted. Orchid roots are very sensitive to salts (fertilisers = salts) so it's important to keep it weak.

I have been using this for a year and a half, and my results are great.

My mantra has been weekly weakly.

This can be a particularly complex subject, and there are more opinions than there are growers out there, as Bil said, but I believe that some scientific evaluation of plants' conditions in the wild can help simplify it. The following is my "take" on the subject, put together on another forum, but may answer your questions, and some you haven't yet had. Keep in mind that everything (and I do mean everything) is not "black and white", but a matter of degree.

Foliar versus Root Feeding:

• Because many orchids have evolved to be very conservative with their water, they have developed thick, waxy, cuticle layers on their leaves to retard water loss. It's particularly evident in phalaenopsis, for example. Those layers tend to be very water repellent, so would prevent the rapid absorption of the aqueous solutions.
• The areas of the leaf surface that DO absorb are closely associated with stomata (which don't absorb liquids), but again, as a water conservation adaptation, they tend to be on the undersides of leaves, which tend to see less solution exposure.
• Orchids vary all over the map, so some plants may absorb nutrients better through the foliar route better than others, while all absorb them well through their roots.

Water First, Then Feed:

• In nature, epiphytes attached to trees and shrubs basically only get fed only when it rains, and the exudates and collected detritus gets washed down to them out of the canopy.
• That happen almost immediately upon the commencement of rain, then it's nothing but pure water after that.
• The velamen on the roots has been shown to be particularly good at trapping the nutrient ions immediately, and holding onto them, so they won't be washed away by the continuing downpour - another evolutionary adaptation for their "niche" lives.
• If you water first, you saturate the velamen, and the plant can no longer absorb the nutrients from the later-applied solutions as well.

Urea versus Non-Urea Nitrogen Sources: There is a lot of discussion as to whether urea may be directly absorbed by orchid plants, and the "common knowledge" is that it must be decomposed into ammonium compounds for absorption, but that's not strictly true.

• Nitrates and ammonium compounds are poorly absorbed through the leaves, but are preferentially absorbed through the roots.
• Urea has just the opposite affinity, which is why many "Green Up" products sold for lawns are loaded with urea.

Formula & Concentration:

• Orchids are about 85% water, 14% carbon and nitrogen, and 1% everything else, combined.
• Analyses of the "throughfall" and "trunk flow" of water cascading from the leaf canopy and down branched to epiphytes (bil was incorrect - it's not my data) has been shown to be <25 ppm total dissolved solids (TDS), with almost all of that being nitrogen.
• There is no such thing as a "bloom booster". A plant is genetically programmed to bloom to its maximum potential, and a well-grown plant will do so. The best we can try to attain is to not do something that detracts from that.
• Rotating fertilizer formulas - unless you have poor ones - is a waste of time. That plant in nature sees a nearly identical "diet" at every feeding for its entire life.

Watering Frequency & Volume This is well above feeding in the plants' "Maslow's heirarchy" of needs:

• Growth of a plant is more about fixing carbon than anything else. That primarily comes from CO2 in the air, but watering affects that capture.
• There is an enzyme within plants that can react either with oxygen or carbon dioxide. When the water supply is readily available at the root system, hormones signals are sent upward telling the leaf stomata to open, which allows the "inhaling" of more fresh air, containing roughly 4% CO2 at this point, and the "exhaling" of the O2 freed during carbon fixing.
• If the water supply is lacking, as happens when we water infrequently, those hormone signals are not sent, the stomata stay closed, and the CO2/O2 ratio decreases, lessening the probability of that enzyme to fix nitrogen, hence slowing growth.
• If one does the calculations associated with carbon fixing, in order for a plant to gain 1 kilogram of mass, it must process roughly 210 liters of water, and only 10 grams of fertilizer elements.

So summing all of that up, I have adopted the following regimen:

• Use a high-nitrogen fertilizer formula. I like K-Lite (12-1-1-10 Ca-3 Mg)
• Make sure the formula is complete, with all of the trace elements.
• Apply it at a very low concentration (I use 25 ppm N) at every watering.
  [*[Select a potting medium and container that allows frequent watering without suffocating the roots.
• Flood the pot at each watering. Not only is it irrigation and feeding, but it aerates the pot and flushes away fertilizer residues and plant waste products.

I have been growing orchids for over 40 years, and my regimen has evolved throughout that period, ending up with that about 5-6 years ago, and I have never seen my plants do better.

^^ What he said^^ ;)

I don't disagree with much that Ray had to say, except I haven't joined the K-Lite cult. It is a lot to absorb when you were probably looking for a simple and reassuring answer. Here's my attempt.

I would interpret "Never give a dry plant fertilizer" to mean don't fertilize a water stressed plant. But if you are drenching thoroughly with a weak fertilizer solution it isn't really a concern. "Don't water on the week you fertilize" could be a precaution about over-watering in addition to that fertilizer drench.

So, no need to pre-water, just make sure you water thoroughly when you fertilize. Personally, 1/2 strength twice a month is at least 4 times the amount of fertilizer I use, but isn't outside the typical range of recommendations. And make sure you are using fertilizer with calcium and magnesium (unless you are sure your hard water supplies them) and at least the basic micronutrients.

For most people, as long as they do fertilize occasionally, fertilizer will never be the thing that limits their success with orchids. And no matter how much people wish, fertilizer will never make up for whatever other problems you have with culture.

I don't view the use of K-Lite as a cultish thing; it's an experiment!

So far, so good.

And to throw in yet another set of opinions:

• I disagree with the Klite experiment's premise, preferring a fertilizer with nearly equal K and N, or lower N. Phosphorus is not needed as much as K or N, but generally is not harmful if plants get more than needed. I can send you a published paper on an experiment that demonstrates this (with orchids) at your request.
• Urea is well absorbed by orchid roots without being broken down first. Another experiment (with orchids) demonstrates this, published results also available if you are interested.
• I think most of us agree that dilute fertilizer is best for orchids. While we may disagree with one another on the best orchid fertilizer, I think most of us would agree that any water-soluble fertilizer formulated for orchids or houseplants is probably OK as long as it is not over-applied. The earlier advice to not apply fertilizer to a water-stressed plant is also sound advice.

And I have 48 years of experience in medium to large size commercial orchid nurseries in Denmark, Germany, Holland & England (the largest had over 15 acres under glass).

They all water first, fertilize next.

So I beg to differ with those who experiment with other schedules.

Oh my goodness, thank you all or your input. Will be trying a weak weekly routine, with a liquid fertilizer that contains calcium and mag.