Slow release fertilizer

[HiOrcDen]

Hi All... So I received a complementary bottle of slow release fertilizer from an Orchid seller recently. It has an appearance of flat-colored green beads, maybe a couple of mm across.

I believe I may have asked about this within a previous thread, though I cannot find it!

So, is a slow release like this safe and suitable both for sphagnum moss growing, as well as growing in bark mix? If so, would there be a difference in the frequency and/or amount applied? (in both cases, do I just sprinkle on top?)
The directions say, to apply once per 6 months for indoor. Right now I am only planning to test the slow release beads for indoors, so I can use ice cubes instead of dilute fertilized water. I am theorizing that ice cubes might help stimulate, at least to some degree, the same effect as nighttime temp drops outdoors.

So is it totally safe to use this slow release, in the recommended amount, for both sphagnum and bark mix, and for any species? Are beads this size okay for miniature orchids too? (I mean like 2-3" pot... and if not, should I employ the mix differently?)

Incidentally, would anyone have any alternate suggestions, besides ice cubes, open windows, or coolers, to improve indoor culture? I basically use a west (slightly south) facing window with some gooseneck led grow lights.

And again, I'd like to be sure the slow release is totally safe! And also, in general, indoors & outdoors as well, is it okay to use both slow release and liquid fertilizers at normal amounts, simultaneously? (or specifically, using dilute liquid with every watering vs periodic full strength liquid)

[Ray]

Slow release fertilizers are just water-soluble powder encapsulated in a porous polymer. Once they absorb water, the solution leaks out into the potting medium.

How fast it leaks is determined by temperature. The polymers have a known thermal expansion, so with increased temperature, will leak faster. Your proposed use of ice cubes (don't do that, by the way) will slow down the release rate, meaning the plants will get less food, for a longer time. Without knowing the temperature-release curve and the formula, I'd be hesitant to use it.

The trigger for flower spike initiation in phalaenopsis is a 10°-15° reduction in average growing temperaturefor 10-days to 2-weeks, before returning to the original, warmer conditions.

[Roberta]

I use time-release fertilizer as a "boost" for orchids that need more than the light fertilizing that I give the whole collection with liquid fertilizer. This especially for those that grow a lot (making lots of new plant tissue) during the growing season, especially Cymbidiums and Catasetinae. Helpful for the larger Catts too. You can use it for Vandas if you can "contain" it so that when watered the extracted fertilizer can drip over the (mostly) bare roots. There are little "cages" that can be purchased or you can wrap some up in a piece of nylon from pantyhose. But for most of my orchids, I just use the dilute liquid fertilizer, they don't need much. And time-release as a supplement for those that do need more.