I'd keep it in water were it mine.
Let a good bit of rootmatter grow first then take steps to harden them off to media later.

That piece is gonna make it.
Totally root-able!

Others will chime in soon with more advice. :)

Normally Philodendron bipinnatifidum won't root from cuttings, unlike a lot of other Philodendrons. But since yours had already started to root before being severed then your chances of it succeeding are good. The ideal is to leave it laying on top of soil with the "few little bumps where Im sure the aerial roots pop out from" facing down into the soil. If you can put something over the stem to keep humidity in then the better your chances. I've never heard of them being rooted in water, I think you'd only get a rotten mush out of that.

I've actually done it before. Had a piece of stem that was stilted up on three aerials that I cut flush at the soil line and then transferred it to a pan of water,where the roots regrew pretty fast. The Stem actually never touched the water so perhaps the mush you describe IS a possibility. Laying it atop the mix,as you suggest,is key here because what I assume happened last time was that the stem had been buried and THAT'S what rotted it.
A dry cleaner bag would be appropriate for trapping the humidity. :)

I have done cuttings from a lot of different plants. Most root better in water, some in dirt (rosemary), some will root anywhere (pothos, tradescantia, mint). But I have never been able to root anything in media without covering it to prevent water loss. This cutting is much bigger than anything i have rooted, and I havent a way to cover it (no dry cleaning bags). That is why I am afraid to root it in a pot. I originally wrapped it in plastic wrap but it kept coming unwrapped. I didnt know you could root something just by setting it on top of the dirt O_o

But Ive never had a cutting rot while rooting it in water...Is philodendron b. different?

This is a picture of the stem from yesterday. That little green bump near the petioles appears to have gotten bigger. I am crossing my fingers and keeping a close eye on it.

Before it broke off, it was the main growth point on the plant, so I'd hate to lose it! The main plant is looking rather spindly and bare atm; however, it hastily sprouted a new leaf from a previously dormant side shoot, so I'm sure it will fill in.

It may not rot in water but just to be on the safe side,you might go by Tropic's advice. The reason it would be possible to root it by simply placing it on the mix and not in it,is that the whole thing would be encapsulated in a bag or terrarium or something that traps humidity. When the air surrounding the cutting is fully saturated with water,the water in the tissues of the cutting has nowhere to evaporate to,..therefore the cutting won't dry up and die. Effectively you'd be tricking the plant by simulating the humidity in it's natural environment,where they break off,fall,and set new roots all the time.

If you can get to a dry cleaner,they may just give you a bag,but if you get charged,it shouldn't be any more than ten cents or so.

if you have perlite: take narrow tall container (plastic bottle), cut off the top, put 1.5" wet perlite on the bottom.
position the bottom of the plant just barely touching perlite, wrap the top of container with saran wrap to seal the moisture inside. and bag the whole plant in a large plastic bag or put it where it's very humid (bathroom) but with good light.
i remember a post that was very interesting. the guy cut out the circle from yogurt 1qt container and dropped the cutting inside : 1-2" of water on the bottom, but the cutting was was above it not touching. sealed the hole, bagged. he had tremendous root growth very fast.
i can try to find it.

Update: It has been a LONG month! I am very happy to report the growth of a healthy root!

I had issues with mold on the initial root which ended in the death of the root as well as the death of most of the healthy tissue. DO NOT use neem oil insecticidal soap on a cutting. I used it as a last ditch effort to kill mold, and both the root and the tissue surrounding it sunk in and shriveled within ten minutes.

Things I tried: for the mold, honey and cinnamon. It didnt help. What DID eventually kill the mold- sitting the cutting in water with hydrogen peroxide (3%). i did this for a few days, replacing the water and H2O2 every day. Maybe a tsp H2O2 to a half cup of water. Doesnt need a lot. As long as you can see the surface of the dead tissue being covered in bubbles, it is working.

After this I took the cutting out, and scraped off all the dead tissue. It was extensive. I thought it would die, but I dusted rooting hormone on the areas that had been scraped, wrapped it (the cut end) in damp sphagnum inside a plastic baggie, and set it upright in a jar on the windowsill.

A few days later one of the leaves started to wilt, and then yellow. The other leaves were healthy. After about a week, I decided to check on it. I was not expecting to find a root, but here it is! After a lot of trial and error.

So, tips: if you wish to root a cutting from this plant, dust the end with rooting hormone, then give it a day or two to form a callous. Wrap it in wet sphagnum and set it in a BRIGHTLY lit spot.

DONT try to root it in water- the root may grow, but will die when removed from the water. Dont just set it in a bag/bucket with high humidity. It seems to need moisture against the actual stem to encourage rooting.

cutting

without the bag- two roots. You can see the tissue that was scraped out/off. not much left.

This post was edited by Lauraeli on Sun, Jun 1, 14 at 15:05

Lauraeli...keep us updated on your progress. Thx

Asleep in the garden....are you saying philo stems will root in water easily ? Tell us how to do it. Thx

Good result! Keep us updated

It took 4 months and leaves died except for one but I got roots and what looks like a shoot! I put 7 inch stump in a clear vase with dampened 1.5 inches of perlite and covered [not tightly] the mouth of the vase with Saran Wrap. Every now and then re dampened. The vase was below the windowsill but leaves received sun. I almost gave up but now am excited!!!

now i just air-layer the tip in moist long fiber sphag: the aerial roots near the tip are still white or i see little white root nubs. these grow very fast if wrapped in cling wrap with moist sphag. it needs to stay moist. a couple of weeks (at most 1 month if in winter) and i can pop the tip off. this way i do not loose the leaves.

i lay it on the side to let the cut dry up and callous with roots still wrapped in sphag for a week or so. then it can be potted. i dust the cut with fungiside and wrap it with a bit of coir to keep direct contact with moist soil: it can still mildew otherwise. sometimes i lay it in shallow tub with mix with the tip sticking out sideways dry in the air. and grow it it like that until established. then i plant it vertically.

I went to transplant this guy an accidently took off all the roots. I was going to trim it up a bit and didn’t realize there were no roots further up. Will it root in the dirt? I have had it for a long time. It would be sad if it doesn’t make it.

It will just rot in water, follow the method I posted above. Damp perlite, and hopefully it will sprout new leaves not roots. then put it in with the parent plant. It may take a long time!! Good luck!

it is the parent plant that was cut off. I have it in soil. Hopefully it will root.

Just not too wet! It should sprout leaves, not necessarily roots...

It has one leaf and the spike of another.

If it just leafs and doesn’t root will it just die?