Another picture; the entire plant, for reference. It's about 9 inches tall.

so you just had it for 2 mo? it could be a residue from foliar feed at the nursery. it's quite difficult to remove. swishing in water won't remove it. you could try diluting rubbing alcohol 1 part to 3 parts water or even by half water. it won't harm the plant. but you'll need to go wiping leaf by leaf, supporting the underside. it would be an overkill.
i would take a close-up of one leaf ev 3 days and compare the photos to see if spots spread.

This post was edited by petrushka on Tue, Apr 8, 14 at 16:43

I agree that it looks like residue from a fertilizer or pesticide application.
I would not be alarmed by it. Over time it will go away. Your tree looks pretty healthy to me.

Do you have hard water? That's what it looks like to me, mineral residue from very hard water.

As it happens, I checked the water softener and that seems to be the root of the problem? The spots are subsiding a bit now that I've fixed that; but thanks for the help and suggestions, I was really in the dark on this one and it's reassuring to hear it looks as though it's doing OK!! Thanks again!

great!
kira, i have a question:
i think your plant looks great, but it does have a very thick trunk and kind of uncharacteristic small flat umbrella-like crown.
it looks like a bonsai tree or at least a dwarf.
did you buy it like that?
i'd love to see the close-up of the trunk with branches radiating from it. can you show us?

Ah, yes, the trunk is about as thick as my thumb! I've got to admit though, I've never had a citrus plant before, so I'm not sure how unusual that is, but I can provide pictures, definitely!

I did buy my tree like this though, it's always been the same size, though {{gwi:82673}}

Here are some pictures of the {{gwi:82674}} for you; {{gwi:82675}}, {{gwi:82676}} and {{gwi:82677}}!

Be sure to investigate powdery mildew, a relatively common disease on citrus. Early infestations can be rinsed away with plain water or a mild soapy water. Neem oil can be a preventative and curative for mild infestations.

PM is a fungus disease that begins life on the surface of the foliage, but once it begins to enter plant cells, serious damage can occur.

Do you have any horticultural oil? (Not cooking oil.) A weak solution on a soft cloth would be perfect to clean the leaves of chemical and water deposits. Use the technique mentioned above....cradle a leaf in one hand and rub with the other. Tedious, but effective.

I'd keep some bottled or distilled water on hand for your plants.

it's a very unusual looking trunk. how can it reduce in size like that? i am thinking it could be a graft? but how can you graft inside into the middle? and there are no scars either.
very peculiar!
very pretty plant.
rhizo, how do you recommend diluting hort-oil? i've had a bad experience with it on indoor plants : burned algerian ivy and killed crotons. i'd love to use it for mites, but am totally scared at this point. i used ready to spray 2% solution from bonide.

Pet, Hedera species are very susceptible to damage by horticultural oils...don't know about the croton. If I am using it on a plant that I've never applied it to before, I do a quick Google on 'hort. oil damage to ____________ ' before using. It is safe on indoor citrus, but special care is required for those outside in the full sun.

I would read the instructions on the label of whatever hort. oil you're using, and follow the recommendations. It could be made weaker for cleaning the leaves, never stronger.

Have you done an alcohol spray test on your crotons? I mix it up to a 1:3 solution in a spray bottle and apply it to many kinds of plants for mites, aphids, mealy bugs, scale crawlers, etc. Works great for the ivy, but have never tried it on croton.

Spray to the underside of the foliage.

I should have made a caveat about the oil applications, so thank you for bringing it up. Though these plant oils are very safe for most plants, they can cause injury to some. That rule applies to anything we use on our plants.

It's always a good idea to spend a tiny bit of time researching before applying anythings, even a home remedy. Especially a home remedy. In these days of the computer, there is nothing that you can't find out in just a few seconds. ;-)

Anyone is always welcome to email me directly if more information is needed, or posting in here. There are some very experienced folks in these forums.

rhizo,
thank you for answering. i somehow lost track of this thread, and just found it now.
i do use rubbing alcohol mixes from 1/4 to 1/2 on just about everything, including crotons. both indoors and when they are outside. even sometimes give a quick wipe with pure rubbing alcohol if i see scale traces (honeydew): crotons and ivy and citrus are fine with that.
and even indoor avocado. cleaned it up quick.
i also use it to wipe leaves on amaryllis for greenhouse thrips (am in the middle of that infestation at the moment ;) , in hopes that it will damage the eggs embedded within leaves? (if they are there) - seems ok.
sorry to digress, but the only plant that did not like it - was hydrangea (i was controlling powdery mildew with 1/3 solution?) - the leaves dried up and dropped off over sev weeks, not right away, but still... not very good.
seems when i ask about stuff in sep threads i don't get many answers. so here it comes....just one more question if you see it:
have you ever tried soil drench using alcohol solution?
for thrips larvae specifically, but also may be for gnat larvae? i normally use neem oil for that, but it's not totally effective, just slows down things a bit.
i search thru the web like a maniac - if it's out there, i'll find it. unfortunately specific info is very difficult to get.
i will experiment with hort oil again on just a few ivy branches: diluting it by half to start. they do plague mine on hot balcony and indoors too.
and i apologize again for digressing!

Hi, I know it’s been 5 years, but since you didn’t get an answer to this question, I wanted to reply. The only home solution for soil treatment I know of (and have had success with) is hydrogen peroxide. It is very effective on fungus gnats. I believe it actually kills the fungus that invites them. While I haven’t used it on my calamondin, I have used it on seedlings and not-yet-sprouted seeds. My seedlings were experiencing heavy damping off, while the unsprouted seeds grew a fuzzy white mold all over them. The peroxide was effective for both.

If you haven’t discovered this remedy yet, take a look online for further info. You will find it.

I use a solution with 3% peroxide to disinfect seeds and I also use it in spray form and add it to water to keep it sweet while i'm rooting or even just for regular watering, I as read that's a bonsai grower's trick to oxiginate roots in old pots.

how much do you use per 1qt for soil soak? I imagine it's more then 1tb ? I read somewhere that as much as 4tb per 1qt is safe. but I have not tried that. I know that watering with peroxide solution helps with keeping fungus and bacteria in check inside pots.

I think that seedlings are fairly fragile, so how much do you put in for them?

I normally keep standard 3% peroxide solution from the drugstore at all times. it's my #1 remedy ..ok, neem oil can share #1 position too :). alcohol a runner up at #2 :)...ee-rr..and dish soap to save the world and my plants ;)...