Time release fertilizer in direct contact with roots

[JScott]

I'm bad about remember to use liquid fertilizer on a regular schedule, so I use a time release fertilizer. My concern with this is that as orchids tend to do, I have many roots at the surface or right below the surface of the growing media. I try my best to keep the time release pellets from being in direct contact with the roots, but sometimes they work their way down there, and end up touching the roots (I mostly grow in clear pots, so I can see this is happening).

I haven't noticed any obvious harm coming to the roots, no black burn spots where the pellets touch the roots, or anything of that nature, but it still worries me. Is this something I should be concerned about? Have other people who use time release fertilizer noticed any harm to the roots when the pellets touch the roots? Does anybody have any suggestions for keeping the pellets away from the roots? Or am I worrying over nothing?

[Leafmite]

Depends on what fertilizer and what orchids/plants you have whether you need to worry.
I use Osmocote for most of my plants and the more commonly grown types of orchids and I have never had any trouble with it. (I wouldn't use it on some of the miniature pleuros or Butterworts, though). I bought the little baskets that they sell for bonsai and fill them up with the osmocote, then push them into the medium. (my medium is lava rock).

[Roberta]

I just toss the time-release fertilizer pellets onto the surface of the pot, have never seen any problems. Some people put it in the middle layer during a repot, that works too (but requires that one thinks about it proactively... I usually don't remember until I'm done) At any rate, never had a problem.

[Fairorchids]

I use it only on Cymbidiums (a lot), and Calanthes (a little). Have never had a problem.

I know that Waldor Orchids use some on their Cattleyas, which have a lot of surface roots. Never seen a problem there.

A friend tried it one year on his Cattleyas. He probably used a bit more than Waldor. There was no damage to plants, but it appeared to inhibit blooming that season.

[JScott]

Thanks guys! I feel better now. I mean, I've been using time release for about to years now and I grow in mostly clear pots (mostly Catts, Oncidium intergenerics, and Phals, with a few additional odd things here and there) so I can monitor the health of the root system, and I had never noticed a problem, but it still made me a little nervous, so it't nice to hear from other people that it's not something I need to worry about. Thank you for your reassurance.

[orchidsamore]

I use hundreds of pounds of slow release every year.

It never burns nor does it ever over-dose.

I dropped an entire handful (water release) on a 2 inch seedling and it was not worth the time to try to remove it. So I was going to let it die but it never did. I no longer bother to measure and probably use more than recommended as necessary. Some is just wasted.

Two more important issues. Do not use Osmacote in year round hot temperatures like Florida. Osmacote is temperature released. At 90 degrees it releases twice as much nitrogen as at 70 degrees. It is too hard to control (it states this on the commercial bags). It was developed for northern climates where you could throw it on your garden in October and it fertilizes you garden the first warm days of spring sitting inert.

We use water release fertilizers. Too much water releases more fertilizer but also is washing it out.

[SouthPark]

Originally Posted by JScott

I mean, I've been using time release for about to years now and I grow in mostly clear pots (mostly Catts, Oncidium intergenerics, and Phals, with a few additional odd things here and there) so I can monitor the health of the root system, and I had never noticed a problem, but it still made me a little nervous.

Nice info there JS. If you used it for two years now without issues under your growing conditions, then one wouldn't expect to be nervous anymore.

If it were just for say a few months, then that would be a different story.

I've never used time-release fertiliser before - but looks like if used appropriately - no problem.

I just use weak liquid fertiliser - once a month, with a weak liquid cal-mag application in-between (eg. 2 weeks after the fertiliser). The rest of the time is just plain watering of the media. I figure that some chemicals/nutrients is still hanging around in the media somewhere for the roots (to get some of) whenever the media becomes wet again.

Forgetting to use fertiliser sometimes shouldn't be a problem. Just use it every once in a while. I think maybe (also) it all depends on what sort of growing set up we have for the orchids. And one method a lot of people use to get some really good performance is weak fertilisation once a week or maybe once every couple of weeks.

I've never needed to flush out my media or pots before with my less frequent fertilising schedule. But definitely beneficial to heavily flush the media out with water every once in a while for cases where more fertiliser is used.

With time-release ------- definitely, just like a lot of things, if over-done or too much of it, used under inappropriate conditions ------ it could be nasty for the roots and plants. But apparently, if used properly - no problem!

Great question and great thread.

[Ray]

Jerry, can you tell us which "controlled release" fertilizer(s) you consider "water release"?

It is my understanding that, in truth, water and temperature control all such coated fertilizers. The powder is encapsulated in a porous polymer coating having a designed porosity and thermal expansion.

At a constant water content of the potting medium, temperature determines the release rate.

At a constant temperature, the amount of moisture becomes the controlling factor.

[Keysguy]

As my orchids are left to the elements in my shadehouse during the summer (5 months) while I'm in the north country, I use time release 3 different ways while I'm gone.
1) in bonsai baskets that I twist tie to each of my mounted or hanging plants.
2) sprinkled on top of media for the potted plants
3) layered into media during spring re-pot of my catasetums.

#3 method clearly brings roots into direct contact and #2 does probably in excess of 50% of the plants.
Have never had a single issue I would attribute to the fert.

The rest of the year when I am here, I fertilize weekly by hand sprayer.

If it wasn't for time release my plants would go the entirety of the prime growing season here with no food. Unless of course I wanted to pay someone to come in and do it every week.

[SouthPark]

Fertiliser is food of sorts ...... as in 'vitamins'/elements ..... essential elements. I have Angraecum eburneum plants growing outside in orchid pots - scoria media - that haven't been repotted for a few decades, and never received any man-made fertiliser at all.

The roots have actually grown out of their pots though, and some are touching the ground - the soil. And some insects etc are living inside the pots (in the scoria). So they likely get their elements/vitamins from the ground and/or the activity in the pot. These orchids are just beginning to form flower buds on their spikes for this latest round of flowering.

Nearby are relatively big dendrobium (hard cane) ones ------ also growing in scoria media, never been manually fertilised as well for a few decades. They flower very reliably too. These orchids just get their water from either the air or from the automatic lawn sprinkler that waters the lawn (and these orchids along with it at the same time) each night.

As for 'time-release' fertiliser, as long as it gets the job done without ever harming a plant, then that'll be great. The other thing thing is sharing the information about this sort or variety of fertilising method. Great to know what has been workable for others out there.