Confused about orchid maintance
 

I have five "Mini"-Phals (Just Add Ice "Brand") but I have been told they may not be mini's, from Grocery stores (about 2 weeks ago). Should I fertilize them or wait?

I read that 20-20-20 is the recommended mix but according to all I've read the N should not come from Urea. All 20-20-20 brands I've seen contain N from two sources one (the lesser) being Urea. So is it OK to use it?

I have, at home, a box of granulated Miracle-Gro which of the 20% N, 8.1% is from Urea.

Of course it will have to be in solution of 1/2 teaspoon granules to 2 qts of water unless someone tells me differently. Now, how to feed; I understand once or twice a month but is it OK to top feed with a syringe?, and how much?

It has been/is suggested re-potting immediately (even in flower). In one I had trouble getting the plastic pot out the ceramic pot. The potting medium was packed tightly in the center so I loosened some of the potting (but not all), and re-potted it in a larger plastic cup and loosely added dampened sphagnum moss. Then placed it in a small bowl of tepid tap water up to the level of the top of the cup. Hope I've done right.

Robert

Urea nitrogen in fertilizers is fine, and orchids can utilize urea with no problem (this is supported by research). A lot of the bad press over urea is related to primitively-manufactured urea fertilizers that also contained an impurity called biuret (think of biuret as a combination of 2 urea molecules; it can cause plant toxicity at high levels). Modern urea manufacturing processes result in fertilizer with low biuret concentrations, but there is still a concern over urea fertilizer because of past problems.

Your fertilizer should be fine, but I would use much less. A quarter teaspoon per gallon is more than enough; you could even use less (orchids are weak feeders). Once or twice a month is fine. Water thoroughly with regular tap water at the sink, then when the roots are good and wet, water with some of your dilute fertilizer (just pour through the potting medium at the sink, no syringe needed).

I would try re-potting again if the medium was so tightly packed that you can't get it all out of the pot. Re-pot with a fir bark mix or something similar, into a well-drained pot, don't pot in Sphagnum moss (moss will eventually kill the roots unless you are an expert at using moss). Your re-potted orchid should drain very freely and nearly dry out (but not quite completely) before you water again. Remember that nearly all Phalaenopsis die because the roots remained too wet and did not have a chance to dry out between watering.

One more though to add to the excellent advice above. -- Pot in the smallest pot that will fit the roots. When the pot is large, it retains moisture more readily and that leads to wet and then rotten roots!

Guess I'll have to get some other potting medium. There are some at the big box stores so I'll have to pick some up.

Thanks for the information.

Robert

Concur with the above advice. Phals are pretty bullet proof. I fertilize every other week, and let them almost dry out between waterings. Most of my phals came in spaghnum moss and I replanted in a bark mixture. To me the moss tends to pack down over time, retain water for too long, and compress around the roots. But that's just me. Moss may work just great for you. :)

Good advice above.

I've used fertilisers with Urea in before with no problems. There are Urea free ones around usually as specialist orchid ones, but one with Urea in won't kill your orchid and is better than not fertilising.

Two comments on feeding:

1) Orchids are slow growers, so need far less fertilizer than do most other plants.

2) The concentration you apply should be determined to a large part by the frequency of feeding, and probably should not exceed the rule-of-thumb of 100-150 ppm N weekly.

I feed at roughly 35 ppm N at every watering. This time of year, when the sun is bright, so there is a lot of growth driving force, I may water my greenhouse 3 or 4 times/week, resulting. If I used plain water most of the time and only fed weekly, I'd probably go for 100 ppm N.

Ray

I've calculated 2 tsp/gal will give 100 ppm N ,(20-20-20) Miracle Gro, but I'm not totally confident of my calculation. Is that correct? I don't want to over fertilize my orchids.

Robert

Wrong

Fertilizer PPM Calculator

I liked the PPM Calculator site you gave. It works out different than the one I used so I think I'll use it to see how things go.

Thanks, Robert

This one is useful as well. Both the link Nexogen gave and this one are on Ray's website. This one does things the other way around, you put in the NPK from the bottle/packet and the target PPM you want and it tells you the tsp/gal.

Fertilizer Mixing Calculators

Thanks Rosie. Just wish I knew the formula just for my own info.

Robert

teaspoons/gal - Target ppm N / (13.1925 x %N on label).

There is also a very easy rule-of-thumb guide you can use, and that is to divide the factor below by the %N on label, giving you the teaspoons/gal for 100 ppm N.

The numerators by ppm are:

50 - 4
75 - 6
100 - 8
125 - 10
150 - 12
175 - 14
200 - 16

In the case of your 20%N formula, your other calculator had you applying 2 tsp/gal, or 500 ppm N (probably close to 3000 ppm TDS), which would surely have killed some more sensitive plants, and damage the roots of most.

Thanks Ray, I'll keep this in mind (and in My Favorites box).

Robert