fertilizer for orchids

[radhasrikanth]

Nitrogen(N)
phosphorus-44%
potash-K2O
MgO+S-8%
chelated Fe,Ze,Mn,Cu,and B,Mo-0.3%

this is the chemicals written in my fertilizer,pack can i use them .
and some of the leaves in dendrobium and catteleyas have turned yellow, color with black spots.what could be the problem???

[Kmac]

Can you post a picture of the yellowing/spotted leaves? That would be very helpful.

Kathi

[Cjcorner]

Fertilizer for orchids...in general you do an even formula such as 5-5-5 NPK or 20-20-20 NPK (the latter is simply 4x stronger). The first number stands for Nitrogen, which encourages growth and helps turn your foilage green. The second is Phosphorus which encourages root growth. Potassium, the third, encourages fruit development and flowering. There are also micronutrients that can be provided from other sources. My favorite is liquified kelp. It's made a huge difference in my ability to bloom certain plants, and others are throwing multiple spikes. I also use a nice dollop of honey every 3 months or so...but only during warm sunny times. You do not have to use a fertilizer specifically labeled for orchids. But if you don't, be careful of "potash" with too much urea. That can burn your orchids badly. You will be able to find urea information as well as the NPK ratio on the container if you look around a little. The favorite saying around here is to fertilize weakly weekly...every 4th week use clear water and flush pots well so extra fertilizer salts will not build up.

[jerrymeola]

You have a high phosphorus fertilizer that many sources including myself think is bad for all plants especially orchids.

Phosphorus inhibits the plants ability to absorb micro-nutrients especially magnesium and calcium. It also will kill beneficial microbes in your potting mix.

The University of Michigan has done the best testing of fertilizers and recommends low phosphorus fertilizers.

Dr. Martin Motes in his two books Florida Orchid Growing and Florida Vanda Growing recommends against the use of high phosphorus.

The State of Florida has made it illegal to use phosphorus in the summer months.

Florida commercial growers are using a 17-3-17 formula with Magnesium and Calcium added in summer growing season and a 7-0-44 mix for winter root growth.

A balanced fertilizer 13-13-13 or 20-20-20 is a decent compromise.