Should I mix Osmocote in the soil at repotting time?

[Clicio]

There is always the possibility of mixing slow release fert directly into the bonsai soil mix at repotting time (early Spring).
Is it a wise thing to do? I keep wondering about one or more of the little pellets exploding inside the rootball and doing real damage. In short, is it safe? Does it work?

 

[0soyoung]

Prills don't explode (what an image! ).

Some mix the prills in the soil/substrate. I don't because I don't have troubles with them washing/blowing away when simply strewn on the surface. I figure if it as on top the fert has the best chance of being utilized (versus prills at the bottom of the pot just contribute to run-off), but it probably is not a big deal. So I think do as you please.

On the other hand, if you are growing stuff in garden soil and plastic nursery pots, pots blowing over can be a problem, in which case mixing in the soil saves fert.

 

[Clicio]

Prills don't explode (what an image! )

OK, exploding was sort of a poetic license...
Let's rephrase it:
Releasing all the fertilizer at once for some reason?
Nah, you have already answered that, thank you @0soyoung !

 

[one_bonsai]

Put it on top. Fertiliser leaches downwards

 

[TN_Jim]

I don’t think osmocote explodes, just slowly deteriorates like a salt lick...unlike Florikan (similar), those green gel tabs in nursery mixes, can’t say I like that shit

I’ve used osmocote and have just tried to catch as much as possible at first, and put back on top, any lost or retained..no seen issues. As I put more things in bonsai pots, I haven’t put osmocote back or reapplied.

 

[leatherback]

I do mix in every once in a while. Not osmocote. I have grated horn fertilizer, some form of bonemeal

 

[Alain BERTRAND]

Put it on top. Fertiliser leaches downwards

Yes, there are studies that show that top dressing of SRF/CRF is a little bit more efficient than mixing in it the substrate. Nursery professionals do it for speed.

 

[Wires_Guy_wires]

I throw some fertilizer and old substrate in my new bags of soil and water it. I'm not a big fan of osmocote; some pellets take a week to break down, others take years. The release is a bit unreliable for my taste.

Pre-fertilizing is somewhat of a discussion point. I am in favor of it because I've been doing it for over a decade in potted plants and almost a decade in the lab where it's standard protocol to do so.

 

[just.wing.it]

I know if you get a tree from Brussels Bonsai, fertilizer balls seem to be a major component of the substrate mix, like 20%.....its kinda ridiculous.

 

[Jeremy]

I mix osmocote in my pots after the trees are tied in. We regularly have summer temps in the mid 30's celsius with the occasional 40+. They seem to last longer this way without all exploding at once on a hot day

 

[Shibui]

I mix controlled release in with all my mix before planting. Technology has come a long way since the first coatings which did have a tendency to dump fert in hot weather but even then I never saw any harm done even though it gets pretty ho here.
Most of the manufacturers now have options for tapered release - more early for fast growing plants like seedlings or a gradual build up and most of the release later in the cycle which suits what we do better. There's also the options for different release lengths from 3 months though to 18 months. I get the longest term release I can to last a whole year and through to next spring.
Controlled release is a great backup to provide a constant low level release of nutrients even when I forget to apply the fortnightly dose of liquid or solid.

Last time I read the guidelines the preferred method of application was to apply the prills in dibble holes into the root ball. Second best was mixed with the soil before planting. Least effective is sprinkled on top - the prills are not in contact with moisture to release the fert for much of the time and I assume sunlight would affect the coating? While fert certainly does leach downward the majority of the roots are in a layer at the bottom of the pot so not much gets past them.

I have used several brands and found it completely safe and works very well for me.

 

[Anthony]

Not Osmocote .
Look for Multicote, designed for use at 30 deg.C
from Israel I believe.
Good Day
Anthony

 

[Clicio]

Thank you all, very interesting discussion.
I will mix the prills into my mix next repotting season and let you know the results.

 

[sorce]

Good 0so is up there, he is the one person I trust that uses it.

We can't "Kleenex" osmocote.
Don't call exploding green balls osmocote of osmocote is truely solid and stable.

That said, climate matters.

I still stick by my understanding of it as complete foolishness, since there is no version of it sold for pots with no dirt that get watered 2 times a day.

I mixed Biotone In my soil one year, and it remains my best season of growth.

Sorce

 

[Leo in N E Illinois]

There is always the possibility of mixing slow release fert directly into the bonsai soil mix at repotting time (early Spring).
Is it a wise thing to do? I keep wondering about one or more of the little pellets exploding inside the rootball and doing real damage. In short, is it safe? Does it work?

For the most commonly available brands of coated, time release fertilizer, the rate of release is temperature dependent. My climate varies from -32 C below freezing in winter to +32 C above freezing in summer. This is pretty extreme. IF you can find a coated fertilizer designed for you typical temperature range, then it is a good thing. Do not overdose your soil.

I had a pine that looked like it needed nitrogen. I top dressed with a good dose of a coated fertilizer. A month later the tree still looked chlorotic. This was spring, weather was running 5 C to 15 C, at the warmest. It was unusually cool weather, but it did not occur to me to take the cool weather into account. So a gave a second "heaping dose" of fertilizer. Finally the prevailing wind shifted, and summer kicked in. Daytime highs of 30 to 35 C. Bang, tree turned green for a day or two then suddenly turned the most frightening yellow and gray. All the new growth died. The tree was being poisoned by excess fertilizer. I had to do an emergency repot. Put the tree in new potting mix with zero coated fertilizer. The tree took 2 years to recover. The third year it was finally growing normally.

Result, I still use coated fertilizer, mostly as an additive to pots with young trees that I am encouraging to grow rapidly. You must keep in mind that coated fertilizers have their release governed by temperature. You can use it to your advantage. It can also be a disadvantage. You just need to keep this trait in mind.

 

[Clicio]

You must keep in mind that coated fertilizers have their release governed by temperature. You can use it to your advantage. It can also be a disadvantage. You just need to keep this trait in mind.

Exactly.
So let's say I repot next month, buds starting to swell and all.
Early Spring here.
If I mix the prills to the soil and they are expected to be released during the next three months, then when Summer hits their effects will be over.
And no ferts during the peak of the summer, January/February.
I guess it will work alright.
Digressing now; even if the temperature outside is let's say 38°C, if moist the rootball should be much cooler, am I right?

 

[leatherback]

even if the temperature outside is let's say 38°C,

Gotta love Brazilian spring!

 

[Clicio]

Gotta love Brazilian spring!

NO!
It was hipotetic!
38°C is high summer. Today is 20°C, end of the winter.
BTW, I hate hot weather...

 

[leatherback]

BTW, I hate hot weather...

Really? Last spring we spent time at a bonsai show you did not think it was hot.
I was loosing weight a pound a step

 

[Clicio]

Really? Last spring we spent time at a bonsai show you did not think it was hot.
I was loosing weight a pound a step

HAHAHAHAHA.
Being Brazilian, I can NOT lose face to an European in matters such as carnival, beer, beautiful girls, huge tropical trees and...
Hot weather.
I hate it.