Can you please add a pic of your cutting?

If that's not possible, the most likely thing to suspect is that your scissors or jar had some kind of pathogen. The other thing that sometimes goes wrong is if the cut is made into woody material. Those cuts rot much more often than cuts at softer, younger growth.

Try separating them into as many jars as possible, so that if one becomes ill, it doesn't affect all. Using jars with larger openings makes it much more easy to get the roots out later, especially if you leave them in water all winter.

You might try adding some hydrogen peroxide to the cutting water. I would suggest about 1 cup of 3% drugstore hydrogen peroxide in a gallon of water. Many grocery stores also carry the 3% hydrogen peroxide, including Walmart.

ZM

I found that rooting cuttings in water doesn't work for me. I root all cuttings in a good soil less mix and use rooting powder. With all cuttings I find you have to be scrupulously clean with your tools and pots. The cut end is like a wound and is easily infected with bacteria. I've also found that putting the cutting on a warmer place discourages rot in cuttings. Last year I used my heating mat for all my geranium cuttings rooted in soil and I never lost 1 plant

Did you try rooting them in any other way? I mean there are many rooting substrates you can try. I personally like rockwool, but there are many more. If you don't get roots with your system maybe you should try with root riot. These cubes are super spongy, so roots can develope faster in it. Also, if you didn't, try using some hormones. I usually use one called clonex (gel form), you just need to soak the bottom of the stem into it (about an inch) and then place it in the substrate or propagation system. Don't apply too much gel because an excess could make the stems roten too.

Whatever, if the stems get rotten it's usually because they need more humidity. Another thing you can try is using a little greenhouse to keep those humidity levels high enough.

Totally agree with the hydrogen peroxide sugestion, and also with the enviroment temperatures. Cloning tools must be super clean and temperatures never under 65ºF (18ºC).

I confess to having no experience with rooting cuttings in water as I have always used potting medium, sand, perlite, vermiculite, or a combination of the above. But I'll add two things to the advice that you've already received as they can contribute to your success no matter what method you use.

Don't make your cuttings too long as that will greatly increase the chance of failure. If you remove twelve inch stems, cut them in half and root them both.

After you remove the cutting from the plant, trim the segment by snipping just below the node. The node is the sweet spot; that's where the roots will emerge. The internode, that piece of stem between the nodes, can rot when left dangling in water.

Coleus is a very easy plant to propagate. I've never tented my cuttings or used rooting hormone when rooting my coleus cuttings every fall. I use my bark based potting medium, insert three cuttings of about 5 inches in length into the small terra cotta pots that I use for propagation. I fill three or four pots and grow them happily all winter.

Honestly, I expect each stem to develop roots in a few days and so should you.

they are not aquatics ...

try this method ... dampen some media .... find a pot that will fit in a clear plastic bag ... small pot.. quart bag ... larger pot.. gallon baggie ...

take some 3 to 4 inch cuttings.. use a razor blade to make a clean 45 degree cut.. and dip in rooting hormone... not for the hormone.. but for the fungicide that is usually in such ... [buy one with a fungicide]

stick 3 to 5 cuttings... in a small pot ... cover with plastic bag... place in bright place.. but not direct sun ..... and walk away ...

week later... come back.. remove bag ... pull on cutting... if it starts to come out.. with no resistance ... no roots ... if there is resistance .... they are rooted ...

the bag should remain a bit foggy ... if not.. add more water... since the piece has no roots.. it has to get the humidity thru the leaves.. hence the bag.. aka greenhouse ....

if you insist on doing it in water ... change the water every day ... and do pot them... as per above.. as soon as you see any root nodule ... do not let water roots get real long ....

a razor blade... might be the difference.. if you are crushing the stem.. with scissors or some such ...

ken

https://www.google.com/search?q=rooting+coleus&ie=utf-8&oe=utf-8

Quite a bit of poo-poo'ing going on here from those who haven't really tried this. I do many Coleus cuttings every fall, sometimes as few as 50, sometimes as many as 150, put in water, and left there until spring, only adding water as needed so they don't dry out. After bringing in around 100 potted plants, there's no room for pots of Coleus also (unless it's cuttings stuck in existing pots, as temporary winter companions,) just jars in windowsills. I don't change the water, or use a razor blade, or anything else unusual. Here's one shot of one small area. I have Coleus allllll over my yard, all saved.

I use pieces as big as possible (stopping short of cutting into hard, woody material) to keep their numbers as low as possible, and to start spring with the biggest possible plants. Some cuttings are 2-feet tall.

Steel, if you come back to this discussion, I wonder if your plants had already gotten too cold? Waiting until panic night, the first night of frost, can mean that plants have already experienced a few nights near freezing. Temps near/below 40 seem to freak Coleus out, they are much more unlikely to take root after that. My only problems have been the years when I waited too long like that.

I'd been doing this for many yrs in OH, and continue to do it here in AL.

Here's a crazy combo pot from last winter, with Coleus and various other plants cheating winter by jumping inside for a few months. I cut the Coleus & stuck stems into the pot, takes a few seconds. A denizen of shade for summer, a sunny window keeps Coleus looking great during winter. Potting like this is a newer method for me, within the past few yrs. Before then, it was nothing but jars of water, which is still my main method for saving the bulk of the cuttings, since I want to save so many. This pot has only about 4-5 pieces of Coleus, stuck in the pot about 2 months before this pic, (seen in ground in the above pic.)

They are the same Coleus, saved over several winters as seen in this pic, from 2012, haven't bought any new ones since:

A few days later, everything had been chopped up & put in jars, ready to come inside. They can be separated into more jars later, until the roots form a massive tangle. Any not separated by then get left together & planted in a clump in the spring.

pshaw rhiz ...

if one method doesnt work for someone.. offer another method ...

i am wondering if you all use city water .. and maybe OP is using well water.. and for some reason ... it just isnt doing the job.. so i offered a different way to do it ...

C in a glass of water should be bulletproof.. but if its not working.. whats you alternative????

ken

No doubt, the various responses make for a robust conversation. I'm sure Steel is aware of other methods of propagation, but asked particularly about cuttings in water, not "how should or could I propagate Coleus?" Sincerely sorry if I sounded anti-other-responses! Just trying to address the asked question.

I'm not saying that putting cuttings in water is the best way for anyone, or an only method anyone should try, just that it should work, generally. Putting cuttings of anything in water would rarely be my first choice, but it happens to be, to me, the easiest way to save Coleus since I have a ton of house plants and want to save massive quantities of stems in only the space on windowsills. Under different circumstances, I would much prefer to stick cuttings right into pots. This year, I've started doing a lot more of that in pots where the Coleus can stick up, over the other plants (pots that I'll be making sure have a good spot near a window.)

Not a fan of the inherent pessimism of sticking a cutting in water, generally. It may be subconscious, but the thought process is, "If it takes root, I'll find a pot for it." It's not only pessimistic, but add extra, unnecessary steps to the propagation process.

"What's in the water" could be a worthwhile discussion to have. Some tap water, softened water, well water, can have various substances in them that some plants can't abide.

To anyone/everyone, I would encourage folks to experiment more with Coleus (or any other plants in which they are interested) during better weather, before it becomes a "do or die" situation. Then one can approach fall cuttings with the confidence of repeating whatever methods that they have seen will produce their desired result, at their particular location with their particular water (and other variables,) which is so important to any successful propagation endeavor. If one has doubts, that will affect the results.

If it gets down to panic night when frost is inevitable, and there have not been successfully rooted cuttings yet, popping the roots and crown out of the ground and potting it up would be an option too. Trim if/as needed so it fits in the house.

Tiffany, I put coleus cuttings in water and have no problem rooting them. I would like to keep them in water all winter for the same reasons you a stated. The problem I have as that around late Feb./early March the stems start to rot where they touch the container. Any suggestions for me to avoid that problem without having to pot the rooted cuttings? I like to wait until midMay to pot the cuttings so they can be outside or in the garage then. I use regular tap water that hasn't been softened.

EVERYONE HAS THEIR OWN WAY... WHEN ROOTED IN WATER I CUT DIAGONALLY "IN BETWEEN" LEAF NODES... RESULTS ARE PICTURED...

AND FOR POTTED ONES I CUT JUST BELOW LEAF NODE ...SOMETIMES I USE ROOT HORMONE THEN STICK IT IN POTTING SOIL AND LET IT BE BESIDES AN OCCASIONAL DRINK :)... MINE R ON MY TV CONSOLE IN A NORTH/WEST CORNER... WORKS FOR MY PLANTS :)... STEEL SKIES ...
WISH YOU THE BEST OF LUCK N HOPE YOU FIND SOMETHING THAT WORKS FOR YOU ...

Steelskies, I thought of something else to ask you. How much time elapsed between the time you cut the stems and when they were put in water?

Gail, your first pic shows wonderfully how Coleus can take root anywhere along the stem, nodes irrelevant for this particular plant. TY for sharing your pics & success stories!

Mnwsgal, could you describe more what you mean about stems touching container? Are you using something with a small opening, like a soda bottle, or a larger opening, like a pickle jar? Is the water staying clear & odor free?

I use various wide necked containers, drinking glasses, jars, etc, both glass $ plastic containers.

The water gets changed frequently and is not cloudy from rotting leaves or stems.

Where the stem rests against the container darkens and the plant wilts as no water gets past the rotting part. This is after they have good roots and close to spring. Perhaps temps are too cool in the basement.

I think I did figure out that if you take a hardened stem, it doesn't work as well. seems its better to take a "soft stem"

I save some Coleus varieties from year to year, maintaining a couple pots of each and then going into heavy propagating mode a couple of months before plants are ready to be hardened off in the cold frame. They're generally easy to root placed in moist (not soggy) soil in pots in a flat covered with a high-top vented plastic dome (avoids rot that can occur when foliage is resting against the damp sides of a plastic bag).

I root a few things in water, but limit that because I'm too lazy to keep changing the water to keep it fresh.

While coleus are usually fast rooters, rarely a variety is sluggish about rooting and growing indoors under lights. Same goes for wax begonias. Most propagate easily from cuttings, though I have a hard time getting roots to form on cuttings of "Big" (red-flowered bronze leaf form).

I agree on the need for warmth (70F or above is best)