growth and bloom fertilizers have been recommended for cymbidiums.

[LouisW]

Im definitly not an expert on cymbidiums, but i do have one so this is a good thread for me too.

That said I have noticed that, more than other orchids, growth and bloom fertilizers have been recommended for cymbidiums. The higher nitrogen formulas(the first number in x-x-x on the label) are growth boosters, and the higher phosphate fertillizer (the middle number in x-x-x) is a bloom formula.

if any one else can elaborate on this it would be very helpful, as i am not positive of this.

[JLu]

LouisW, you have opened a never ending controversy. There are believers on all fronts of this issue and you will get all kinds of replies to your question. No one has all the necessary data to prove their position.

So my belief (and I think it's mainstream thinking)....plants use a lot of nitrogen so they need enough for optimum growth. Personally, I use 50-75 ppm nitrogen at each watering. There are some excellent orchid growers who use 125ppm and I can not say that's wrong. At least one Paph authority says Paphs need no fertilizer whatsoever. I don't buy that. However...nitrogen promotes foliage growth and too much (whatever that is) can result in lots of foliage and no (or reduced) bloom. This effect (foliage with reduced bloom)is widely believed across horticultural interests and I believe it.

Phosphate is a more controversial and potentially dangerous issue. Even though P is a macro nutrient, it is needed in smaller quantities than nitrogen. You can actually kill plants and permanently poison soil with phosphates. Admittedly, this is unlikely with orchids where they are potted and flushed frequently, but absolutely in soil phosphates can be bad if over used because they are not mobile (do not leach) in the soil and accumulate over time. I'm going to say (with expectation of some criticism) that so-called bloom formulas are rip offs and do nothing good with a huge potential downside. I recommend against them unless you know by foliage analysis that you have a P shortage.

Remember, in the wild, most orchids get slight fertilization versus their terrestrial counterparts, so they are evolved in a nutrition poor environment. I think that also suggests not falling for fertilization schemes intended (but not necessarily suited) for regular garden plants.

You'll get every suggestion on earth here. This just mine.

[jerrymeola]

If you average the higher nitrogen with the higher phosphorus you get a balanced number. Why stress the plant twice. Use a balanced fertilizer all the time unless you can identify a specific need.

[JLu]

Jerry, I agree with you completely (on the bag stated formulation), but there is a difference between the reporting of nitrogen and the reporting of phosphorus and potassium.

Nitrogen is reported as percentage nitrogen in the product and further broken down by law into the proportions of nitrate, ammoniacal, and urea sources of N.

Phosphorus is reported as % phosphorus pentoxide (P2O5). Since P makes up only 40% of P2O5, the amount of P in the formula is 40% of the reported number.

Potassium is reported as potassium oxide (K2O). So the K in the formula is about 57% of the reported number.

In 10-10-10 there is 10% by weight nitrogen, 4% by weight phosphorus, and 5.7% by weight potassium.

Pure water MSU is 13-3-15-8Ca-2Mg. So it's really low in P since it's
40% of 3 or about 1.2%. Personally I like that low value because I have good luck with it.

However I do not disagree with your "even" recommendation such as 10-10-10 or 20-20-20 as long as it's known that these numbers don't tell the entire tale.

[Hummer344]

I use a little growth stuff for a few weeks in the spring. After that, its balanced stuff the rest of the year. I think that the extra nitrogen helps the plants put out better(& more) growth. The rest of the time I can't be bothered. Oh, ya, I can't remember either. To much confusion on when & what needs what. LOL. As far as cyms go, the cooler the fall nights are, the better & more spikes I get.

[LouisW]

Oh wow. I actually meant my original post as a response to anther persons question. I don't know how it ended up as a new thread.

[LouisW]

Though I am glad I accidentally opened this discussion.

I have been trying to think of a reason that plants in the wild might experience this nutritional change over their growth and blooming periods, but I could not logically deduct one, so for now I will stick with "balanced" fertilizer for more natural conditions. Hummer334 you also make a good point. I have been stressing out about which plants need what fertilizers and sometimes i feel like im poking them and saying "bloom why don't you!"

Ill just use 20 20 20 year round and pay closer attention to the temps.

How about micro nutrients? I only know a little about the importance of calcium and magnesium but if anyone could elaborate on other nutrient relationships and effects I would love the info.

[Andrew]

As JLu implied, this topic is a big can of worms. While solid scientific studies of nutrient uptake have been carried out in non-orchid species, most of the info about orchid nutrient requirements is a mixture of anecdotes and studies by hobbests and horticulturists that, to be honest, lack experimental and statistical rigour (it could be worse, you should see some of the BS science that gets touted as fact in aquarium circles).

There are two schools of thought, one is that if you feed continuously with a single complete fertiliser that will supply sufficient nitrogen, phosphorus and potassium (why do you guys never discuss potassium?) the plant will use what it wants, grow strongly and flower of its own accord. This also has the benefit of making a mixed collection easier to fertilise.

The second school of thought is that seasonal flowering orchids have distinct nutrient requirements during different growth stages. "Green" growth is a nitrogen hungry process due to the heavy nitrogen demand in producing chlorophyll. Thus, when the plant is actively growing leaves increasing nitrogen will meet this nitrogen demand. During flowering phosphorus and potassium are supposedly in more demand so the proportional concentration of these macronutrients are increased. Phosphorus is utilised in nucleic acids, phopholipids etc. It's utilised in leaf, root and flower growth both structurally (DNA, cell walls) as well as in energy production. Why bloom fertilisers contain so much of it is beyond me. Presumably, it's a throw back to flowering annuals etc where flowers are produced on mass at a high energy cost to the plant. From both the scientific literature on typical perennials as well as those who have tried to look at orchid response to nutrient availability (as mentioned above, not by the most scientific means), phosphorous requirements are pretty low and grossly increased phosphorus contents in bloom boosters probably says more about the inexpensiveness of phosphorus than plant requirements. Be aware that mycorrhizal fungi are often sensitive to phosphates. If you are growing anything even mildly myco-heterotrophic (doesn't apply to most orchid growers) or if you are using a fungal agent like trichoderma (or worm tea for that matter) you'll want to take care that you're not oversupplying phosphate to the detriment of the fungi. The often overlooked macronutrient is potassium. It's a major transport and channelling ion in plants. I don't know why it's rarely discussed in orchid nutrition because its effects of flowering, fruiting and disease resistance (Cymbidiums flower in the cooler, more stressful months) are well documented for other plants. Most orchid bloom boosters in Australia have increased potassium compared to growth formulas, of course we don't used the oxidised states of nutrients to express NPK's so it may be more obvious when reading the fertiliser packets. To summarise the growth/bloom fertiliser method probably has less to do with starving or pushing growth as it has to do with meeting demand with minimal waste, although some orchids (eg Dendrobium nobile) do respond to nutrient starvation.

As for which method is better, take your pick. Both approaches have merits and I'll still happily listen to both the one and two fertiliser parties. Personally, I changed to using only one fertiliser for my Cymbidiums a few years ago and I'm now going back to two because I just haven't been getting the count and quality that I used to get (low K or high N?). Do orchids receive this kind of seasonal shift in nutrient availability in the wild? Most likely not but if you've ever seen orchids in the wild you'll find 99% are scrappy, sorry excuses for plants that have no place on the show bench.

[JLu]

Very good information, Andrew. Great post!!

The following is not in response to your post, but instead a couple of things I meant to say earlier.

There is a belief in horticulture that you can not over fertilize because the plant will just use what it needs and ignore the rest. I don't agree because you can poison the plants growth area and do considerable damage with too much fertilizer. Again...it's hard to relate this to a potted orchid if the medium is well flushed frequently. I just point it out for your consideration. Plants are not usually going to die from under fertilization, the opposite is not so obvious.

Additionally, the above appears to be untrue at least with nitrogen. Extra N will spur additional foliage growth. Anecdotal evidence (which I strongly believe in this case) is that this excess foliage growth is less resistant to disease, including fungal infection, than plants that do not get excess N. While I admit that I'm not much of a botanist, there are several reasons that this could be true. Observations from knowledgeable growers suggest that daylily plants getting a high N exposure are more likely to get a rust disease that is specific to daylilies. There are other observations as well. I can't prove it, but I do believe it (and I'm usually suspicious of anecdotal observations).