I would suspect differences in light would be the culprit. With higher light the leaves will grow lighter in coloration. Also a fast change to this location would explain a leave dropping or two. Otherwise your plant looks healthy IMO.

How often do you water? How old is the smaller plant? Are roots coming out the bottom of the pot yet?

-David

I agree with David in that the one on the window sill is naturally a lighter green because it's getting more light than the one sitting in from the window. But the yellowing leaves would concern me, too. Do you water before it gets too dry? Carnosa has somewhat succulent leaves, so it can be allowed to dry quite a bit, though I don't let mine get anywhere near bone-dry. I guess what I'm saying is with carnosa, it's probably better to err on the side of dry than wet. If the yellowing continues, I would probably check the roots to make sure it's not swimming in too much soil. And another thing I'd probably mention - standard potting soil gets "sour" after awhile. It can happen after only 6 months, or it can be good for a couple years. So changing your soil periodically is a good thing. I have a Hoya fungii that has yellow leaves that don't drop - other than being yellow, they seem perfectly healthy. Upon doing some research, I found that it was likely from my soil being alkaline, so I got a soil acidifier. I'm hoping that's going to bring it back to green...

Denise in Omaha

Just to make it a little easier...I posted your pictures directly. Here's your pictures.

The leaf that fell off last week:
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The other leaves showing yellow:
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The little hoya now after a week with fertilizer next to the parent hoya with all leaves not as dark:
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Welcome, Threnodi. ^_^ First, I wanted to commend you on your detailed descriptions and pictures, which are truly helpful in diagnosing your problem. Particularly as we are able to see how the yellowing starts and progresses.

I wouldn't worry about lack of water being the cause. I wouldn't recommend it, but you can leave a carnosa without water for over a month and it will still not drop a leaf. It takes a lot of abuse to get the better of those succulent leaves.

I also wanted to mention that you are correct in assuming the leaves aren't falling off because of age. Carnosas keep their leaves for so long it seems like they are permanent. I honestly can't even think of a time mine lost a leaf where it didn't indicate a problem, and mine, while not being even close to the eldest in this forum, is a good 10+ years.

The way the leaves are turning yellow from the tips, and possibly also their paleness (although as others point out, they do get lighter in high light) could indicate a nutrient deficiency. As Denise says, if you have started fertilizing your plant and seen no improvement with time, the soil ph is likely your culprit. Even if sufficient nutrients are being provided, if the soil ph is too acidic or alkaline, your plant will not be able to take them up.

It CAN take longer than a week to see the yellow recede, but if you are correctly addressing the problem, you should see results soon. I would keep an eye on the leaves that are just beginning to show yellow, to see whether they progress or start to improve.

Good luck, we all know how distressing this is, and feel for you. Your plant is tough, though, and will definitely make it through your diagnosis period.

Thank you for the replies, and I'm glad to hear the photos were helpful! Is there a proper way to post them directly like Puglvr1 did? I couldn't figure how to do that. ^_^; And it's good to know these guys are pretty hardy...

Peanut, the child plant is about 1 year old, has been sitting in that spot about 6 months, and I'm not sure about roots coming out the bottom--if they are they're not all over the place, I see a few tiny twiggy somethings in the holes that could be roots or part of the soil mix.. is there a safe way to tell? Also I tend to water both plants till water comes out the bottom about once every two to three weeks. It seems like it takes longer for water to reach the bottom of the small plant than the large one, so I might give it more water proportional to the pot size..

Denise, I usually let them get pretty darn dry before watering.. though that might be because I've tried getting plumerias to grow on and off the last few years and managed to rot out every one so I'm gunshy.. >.> That's interesting about the ph though! I don't know how to check that or treat, but I'll look it up! I might also try scooting it away from the window to get a bit more shade, and see if that helps.

Greedyghost, Thank you for the well wishes, and the explanation of how PH affects the plant--I know I have a different soil in the child plant since the parent plant came from my mother..

For now I'll look up PH checking and try to scoot it back from the window, thanks everyone! I'll update if things change!

Hi Threnodi, here's a post from Greedy Ghost...

"To post the photo below, I am using:
img src="http://farm4.static.flickr.com/3058/5788512177_805bd28648.jpg"; with "

Hopefully that helps...just put one at the beginning and one at the end.

Thanks, Pug! ^_^

Your photo host should also have somewhere where they provide the html that you can just copy paste in the Message body.

I'm sorry if we worried you, but if higher light is the reason the leaves are a lighter green, this is not a problem (unless you believe it to be ugly). In fact, your plant is likely to bloom faster in higher sun. ^_^

Hoya roots are pretty easy to distinguish from twiggy bits of soil. They tend to be creamy white or greenish white and reasonably thick. I think peanut is trying to establish how well your cutting has filled out its pot, in which case, there would be an easily visible proliferation of them near the drainage holes.

Ahh, okay! Oh, I'm all for faster blooming, though it sounds like these guys can take over a decade to get to that point, huh? My mom's plant that these guys came from ends up covered it lovely smelling blooms once or twice a year, so even if it takes a long time, I'm looking forward to it!

But I don't want it to be dropping leaves if it shouldn't-- as to the roots, I did see a couple creamy strands sticking perhaps a centimeter out of two of the drainage holes...though when I tried to loosen up the top soil I found a lot of strands there that I think are roots because they all look connected, even though they're thinner and brown...Perhaps it's pretty full?

Hi Threnodi, creamy roots are alive and brown roots dead. I'm guessing the problems with them may have originated from overheating, just because the pot of your plant is black and placed on a metal tray, and the weather is sunnier now. Over or under watering are possibilities too. Once the problem with soil or overheating is corrected, your plant will grow new, healthy roots. If you decide to repot it, try a slightly airier mix, Hoyas like that.

I used to believe that it took carnosa that long to bloom, but after Pepeuve's posts, I'm now a believer that in ideal conditions, carnosa can and will bloom quite quickly.

You can see in the link below a cutting he took of a carnosa that formed 5 peduncles in under a year. I'm not sure how much longer it will take the cutting to bloom, but it's certainly doubtful it will need a decade.

If you ask his advice, he says: sun, sun, and more sun. And if you go to his blog, you can see from his photos that his Hoyas, grown on a balcony in Malaga, Spain, have very very pale leaves.

My carnosa is over 10 years old, however I grew it in dim light for most of that decade, because I didn't know any better. After I put it right up the glass in an eastern exposure, it formed peduncles within a year.

I find it hard to believe that after 2-3 weeks in summer, your plant hasn't had sufficient time to dry out. (In fact, that sounds closer to a case of underwatering and underfertilizing). It is a good sign that you are seeing healthy roots at the bottom.

If you're still seeing a decline, this is what I'd do. First, take it out of the pot and look at its roots. They should all look creamy/tan and firm. You want to be confirming that none of them look brown/black and shriveled. You also want to keep your eyes out for fungus or insects.

If they look okay, then repot it with some extra perlite and/or bark like Kukka suggests, and try and step up the watering schedule a bit. The next time you're ready to water, stick a chopstick or kabob stake all the way to the bottom of the soil. This is just to confirm that the bottom of the pot isn't somehow staying damp through some miracle. It is a little weird that this pot is draining more slowly than the big one. Normally I wouldn't go through this rigamarole, but it's clear something is wrong and we have to start eliminating possibilities.

Here is a link that might be useful: Pepeuve's well behaved carnosa cutting

Maybe that's it...maybe with the weather warming it's been getting too hot, or running out of water too fast being right up in the window in a black pot.. Hm! Perhaps I should look into putting it into a slightly bigger white pot and leave it up close to the sun, and try not to leave it dry as long. It does seem like it's pretty tight quarters in there, when I tried to stick in a chopstick I had to push quite hard to get it far in.

Do you have any advice on how to go about taking it out and looking at the roots/repotting? Heh, I've never got that far before..! Do you flip it over and try to gently hold on to the vines and pull off the pot? If it was in clay or something that curled in a bit on top that would make removing a root bound plant pretty hard though, huh? Though luckily I'm not in that situation..

I see what you mean about Pepeuve's light leaves, Greedyghost! That's really encouraging! East is the one direction I don't have windows in my home, but they're currently sitting in the southern window. I'll cross my fingers for them!