Bonsai fertiliser

[Simpo Two]

I was given a bonsai tree a few weeks ago and undertsand that it needs a little feeding.

Research over what NPK is needed is mixed but I got the impression they should be roughly equal.

I ordered some 'Bonsai Focus' from eBay having been told by the seller it was 1.6 : 2.4 : 2.6 - the most equal I could find. However it's arrived and is actually 1.9 : 0.7 : 3.9. DOH!

What is actually best and will the stuff I got be OK?

Thanks!

[Basil Brush]

Manure from a very small horse?

[Zad]

Over summer, I used to use a balanced formula, just the generic fertiliser from the garden centre. At this time of year though (as you no doubt know) its a good idea to drop the nitrogen level. Normally nitrogen promotes green growth, phosphorus promotes shoots and roots, with potassium promoting general "hardiness". So for this time of year it is probably a reasonable formulation.

Still a bit naughty though, not sending the product that was requested/advertised.

[Simpo Two]

Thanks Zad. I have normal Baby Bio and also their 'orchid' version - but when I did the maths found the latter was exactly the same but half strength, the cheeky buggers.

Ideally I'd like one fertiliser for all seasons, but it's dawning on me that a bonsai is more like a pet than a plant, so perhaps I'll have to tool up. And maybe if a bonsai is just a small normal plant, it needs normal fertiliser but less of it...?

It's a Japanese Pepper - does that affect what fertiliser to get? www.amazon.co.uk/Bonsai-Szechuan-pepper-Zanthoxylu...

Whilst half my degree was plant physiology I have no experience of bonsai!

[Zad]

I must admit I have never grown one of those, looks an interesting little thing. Yep, as you say, they are just normal plants just smaller. The biggest effect of that is that there isn't a lot of soil around the roots to be a reservoir for water, so they can tend to dry out in warmer weather or if near a heat source (which they generally hate).

Its a few years since I grew bonsai, most are now in the garden now as small vaguely tidy bushes that are nice in the autumn, but generally I fed them on a half strength general purpose balanced feed in the growing season (gives them extra nitrogen for the leaves) and then the rest of the year I used a low nitrogen feed (Chempak 8 12.5/25/25 from memory). In the growing season I fed 2 or 3 times a week, and once a week the rest of the time. Watering is a bit of an art. Most of the books say to immerse in water once a week, but never let them dry out. Blahblahblah. Personally I just look at them and see how damp the soil is with my finger. If it seems dry, I give it some water. It becomes a habit just to check them now and then (as you say, they are a bit like a pet). Generally speaking, more bonsai die from being over-watered than under. Too much water causes the fine roots to rot off, which means it cant take up water, so people give it more water...

One big secret. If at all possible, use rainwater. Plants hate the natural salts and chemicals added to tap water. It builds up in the soil around the roots and they end up not happy at all. If you have to, use filtered water or water from a dehumidifier etc, but rainwater is the business.

[Johnnytheboy]

Zad said:

Watering is a bit of an art. Most of the books say to immerse in water once a week, but never let them dry out. Blahblahblah. Personally I just look at them and see how damp the soil is with my finger. If it seems dry, I give it some water. It becomes a habit just to check them now and then (as you say, they are a bit like a pet).

This is the rule for all indoor plants. Ignore the labels as they all say more or less the same thing. To quote from my blog:

I said:

...it's amazing how many clients who buy plants from us on a supply-only basis go on to harm them by incorrectly watering them.

On delivery they will have asked me, "how much do I water this then?"

I will have replied, "the most important thing to do is test the moisture of the soil every time you water. If it's still wet don't water it. You'll also find it will use different amounts of water through the year. But at this time of year I'd say about half a can full of water a week."

What they will have heard is, "Blah blah blah blah half a can full of water a week."

[Johnnytheboy]

Just been and looked in our garden centre: we sell Westland Bonsai Food in little bottles and its NPK is 1.1:3:3 which seems appropriate if your objective is low growth.

[Simpo Two]

Thanks all, sound stuff.

Whilst I don't want loads of leaf growth, I don't really want much root growth either, due to the small pot! Anyway, I'll try another fertiliser as suggested and see what happens.

Or maybe wait until it shows signs of going pale? Leaves are a lovely rich green at present and I've already seen off an attack of very small whitfly.

[Zad]

I don't want to overstate the root growth thing, it just kinda does what it does. Its more the lack of it that stops growth rather than turning it into a rooty triffid. Even if you stop feeding it, it won't just die, it will just eventually kinda look a bit sad and meh. For houseplants I pre-mix some feed in a 2 litre pop bottle and give house plants some of that now and then (obviously usual precautions with kids and pop bottles etc apply).

[Matt Harper]

I have a Star Jasmine that is about 4 years old and lives outside, in a sub-tropical climate. Moving it outside and exposing it to rainwater made a massive difference to it's health and vitality. My understanding (sophomoric as it may be) is that you should never let the soil dry-out and feed sparingly. Mine gets a light sprinkling of feed pellets every 3 months or so.

[Mobile Chicane]

Bonsai really need mycorrhizal fertiliser (Google it).

[Simpo Two]

Mobile Chicane said:

Bonsai really need mycorrhizal fertiliser (Google it).

Ah, commensal fungi you mean (degree still works!). I actually have some of that, recommended when I bought a grape vine a few years ago. Not sure how long the spores last for though. And it's powder not liquid so not ideal for application.