Sphagnum and fertilizers

[sept2256]

I'm trying to use only sphag for some orkids.
How have I to fertilize?
Should I consider sphag like bark or like inert medium and therefore to fertilize as a semi-hydroponic colture?
thank you for your advice,
Pierangelo

[tucker85]

Treat it like inert medium. You do not need high nitrogen fertilizer used with fir bark. use either a balanced fertilizer or one of the low phosphorus MSU types.

[Royal]

Hi Pierangelo,

Plants in sphagnum moss don't need fertilizer as often. I try fertilize plants in bark at every watering, flushing with plain water once per month. For the few I do grow in moss, I only fertilize once per month.

[sept2256]

Tucker,
what do you mean for balanced fertilizer? like 20-20-20 + micro? MSU formula doesn't have in your opinion high nitrogen formula (19-4-23)?
Royal,
have you never tried to fertilize every watering? did you see differences?
Thank you all,
Pierangelo

[tucker85]

Yes that is what I mean. Because orchids are not grown in soil they need to be given the three major elements and the micro (also called minor or seconday elements) also. When a fertilizer contains the major and minor elements it is referred to as a complete fertilizer. A 10-10-10 would be an example of a balanced fertilizer because it has the same amount of nitrogen, phosphorus and potasium. If it has micro elements too then it's both a balanced fertilizer and a complete fertilizer. The MSU formula fertilizers have a lower amount of phosphorus like your 19-4-23 + micros. High nitrogen fertilizers meant for orchids in fir bark and sometimes used with young plants would be something like 30-10-10. In my non-expert opinion either the balanced fertilizer like 10-10-10 + micros or an MSU type like 19-4-23 + micros would be appropriate for sphagnum moss. You don't need a high nitrogen fertilizer like 30-10-10 which is meant for use with fir bark. In that sense you would treat sphagnum like an inert medium although it isn't really inert. I hope this isn't confusing things even more.

[tucker85]

I haven't tried fertilizing with every watering but I know people do and they've had good results. I fertilize weakly, weekly during the spring and summer. I have used balanced fertilizers and MSU formula fertilizers and I have no opinion on which is better. They both seemed to work well for me.

[Royal]

I grow mostly in bark, and I try to fertilize at every watering. I put a few plants in shpagnum and they did great initially. After watering everything on the same schedule, the plants in sphag seemed to react negatively (burned leaf tips, roots turning away from the surface of the media).

I agree with Tucker, orchids in moss don't need as much fertilizer and can suffer from salt buildup or pH changes more quickly. I prefer a somewhat balanced fert formula. MSU is perfect.

[sept2256]

Thank you all for your experience
So you consider MSU formula balanced, even if it has low P? Is P so ininfluent for the grow? and for the blooming?
Thank you again,
Pierangelo

[Orchid126]

I agree with RoyalOrchids. Sphagnum moss holds much more fertilizer than bark, and therefore needs fertilizing less often or weaker strength, or more thorough flushing with plain water.