Fertilizing After Root Work

[jimlau]

I have some trident and Japanese maples. 2 of them have had root reduction (~30%). Do those with root work having been done need a different fertilizer than those not having root work done?

Also in the spring, in general, what are the best fertilizer ratios for maples? I have 12:10:11 slow release pellets.

Thanks.

 

[Deep Sea Diver]

I have some trident and Japanese maples. 2 of them have had root reduction (~30%). Do those with root work having been done need a different fertilizer than those not having root work done?

Shouldn’t make much difference.. However one might wait a couple weeks and then start with 1/2 strength for the first round

in the spring, in general, what are the best fertilizer ratios for maples? I have 12:10:11 slow release pellets.

Tough question to answer off the cuff. The reason is the answer will depend on the stage of development each maple is in, also what one’s goals for each tree are including the time frame for each tree.

I know this may seem a bit complicated, but consider adding fertilizer as merely one way to put one’s foot down on the accelerator for the tree’s growth. The choice of a certain Nitrogen value fertilizer (along with other variables, including growth habit of the tree, ground vs container growing or size of container, amount of sunlight, amount of branch and root pruning done, frequency of application, media particle size…etc) can dictate the speed/amount of growth of a tree.

Conversely taking away fertilizer or lowering the nitrogen content, slowing down the frequency of application etc, is like braking… or at least easing ones foot off the accelerator.

The same can be said about the other variables mentioned above and perhaps a few more not on the list above.

It’s often simpler for me to think about what rough height and type of growth I want first, (masculine/robust growth or feminine/delicate growth) then vary the environmental variables to foster this growth pattern…. Not to mention doing the research and sourcing to acquire a cultivar known for the particular growth pattern desired…. if grown properly.

Hope that’s clear.

Cheers
DSD SENDS

 

[Shibui]

No need for a different fert after root pruning.
Limiting really strong ferts right after root pruning may be advisable. Many sources advise waiting several weeks before adding fert but all my trees have fert in the potting soil so they all get fertiliser from day 1 and does not seem to be a problem.

The fert ratio you've quoted seems way off to me. Very high P and K with lower N relative to the other 2. Maybe check again to see if there are decimal points in those P and K numbers because they both seem very high. having said that i am aware that some companies in the US sell ferts with crazy ratios because growers think that's what they need. Plants all need more N than both P and K. Any K and P above the 1/3 N level is simply wasted as the plants cannot use it. I certainly wouldn't pay for a fertilizer with that nutrient ratio.
@Deep Sea Diver has already given a pretty good guide to what N does so I won't go further there unless you have any questions.

Is the fert you quoted slow release or controlled release? there's a big difference. Maybe let us know the brand or post a pic of the packet so we can pick up on things you may not have noticed or understood.

 

[rockm]

Fertilizing right after root pruning isn't going to affect the trees much. They just can't use it because that process eliminates a lot of feeder roots that take up ferts. What you apply will mostly run through.

The above advice on ratios is great. Depends on what you're trying to do--get a lot of growth to thicken trunks and branching and refining ramification require different ratios, for instance. The first requires a lot of Nitrogen fuel, while the second can be defeated with that same approach.

 

[jimlau]

No need for a different fert after root pruning.
Limiting really strong ferts right after root pruning may be advisable. Many sources advise waiting several weeks before adding fert but all my trees have fert in the potting soil so they all get fertiliser from day 1 and does not seem to be a problem.

The fert ratio you've quoted seems way off to me. Very high P and K with lower N relative to the other 2. Maybe check again to see if there are decimal points in those P and K numbers because they both seem very high. having said that i am aware that some companies in the US sell ferts with crazy ratios because growers think that's what they need. Plants all need more N than both P and K. Any K and P above the 1/3 N level is simply wasted as the plants cannot use it. I certainly wouldn't pay for a fertilizer with that nutrient ratio.
@Deep Sea Diver has already given a pretty good guide to what N does so I won't go further there unless you have any questions.

Is the fert you quoted slow release or controlled release? there's a big difference. Maybe let us know the brand or post a pic of the packet so we can pick up on things you may not have noticed or understood.

For this cyberian elm, i need more ramification. For my maples, most need fast branch growth. Do I need 2 fertilzers then?

Many are 2-3" diameter, 1-2 feet tall. Most need fast branch/trunk growth.


They are in a bonsai mix with component sizes about 1/8" inch (non-organic): fired clay, bark, and lava rock.


Anyway, I see an 18-6-8 I could get. It is slow-release. Is that suitable, given the info I have listed? I already still have some (15-9-12.)have an Oscomocote Smart Release food

​

Thanks.

 

[dbonsaiw]

I tend to throw in slow release fertilizer when repotting. This way the tree has some nutrients in an otherwise very inorganic soil when waking up.

 

[Shibui]

I suspect the 'slow release' you guys are talking about will be controlled release. We used to have slow release compounded ferts but release was unpredictable and only lasted a few months at most.
The newer controlled release eg Osmocote have special coatings that allow very slow and predictable fert release. I find those excellent for bonsai and always mix some into the new soil when potting up.

For my maples, most need fast branch growth. Do I need 2 fertilzers then?

I think fast branch growth and ramification are 2 sides of the same coin. Good growth helps thicken branches. It also allows more frequent pruning which promotes ramification.
In the later stages a lower N fert might be useful to slow growth and promote shorter internodes and finer twigs for the final ramification but initially just aim for growth.
18-6-8 is reasonably balanced and should promote good growth. 15-9-12 is relatively high in K so probably aimed at flowering or fruiting plants but it will still promote good growth.

Inorganics in potting soil is good but many don't hold onto nutrients so we need to remember to reapply regularly.

 

[Glaucus]

12:10:11 is an odd ratio. Things like 18-6-8 and 15-9-12 make more sense. That low in nitrogen makes more sense very late in the season, assuming the theory that low nitrogen is correct to slow down growth and harden off plants for fall.

Doesn't mean it is bad, but in general you want more nitrogen than the others. And in general, you want phosphate to be lowest.
But it also depends on your substrate or soil. It is still very early in the season, though.
And if you repotted into fresh substrate, it probably has some trace fertilizer in there. Even more so if it is in soil.

First let it grow, then fertilize light. Then fertilize some more. The first thing a fast growing plant needs in the middle of the growing season is nitrogen.

Adding slow release pellets to new potting soil is always safe, assuming you follow the recommended dosage. But I don't know if osmocote should be used with soilless substrate according to the manufacturer.