It will make no difference one way or the other, or if you even cut them off. I leave mine too but direct to soil.

Coolest was having a common philodendron once, sitting in a shady north window, that began to use its roots to climb the wall (which must have moist to some degree). Those roots are for both support and moisture.

The plant wouldn't feel "better" about it, otherwise those roots would have been down to the ground/soil already. They're up there looking for some sort of support to cling to. Humidity/moisture encourage those roots to grow. Very common for Philodendrons and other climbing aroids.

I train my phil with straws. :)

So, after a few days of an aerial root being stuck into the mix and after reading all of your replies I took it out. It had some pieces of the mix (bark and turface) stuck to it unexpectedly strongly. Could it be very fine root hairs clinging along to the mix particles? I could not see anything like that, but this is totally waking up the easily-excitable kid experimenter in me.

Also, the under-ground part of that root looked redder/livelier and plumper/thicker than the above-ground part of the same root.

These two things tell me the root was happy there. I am going to try this again with a couple aerial roots this time and for a longer time. This is fun!

Asleep, where are the straws you are talking about? I must be missing something very obvious in the picture.

Sorry...only one root is being directed at the moment. That thick root that's already secured itself firmly to the soil was trained in the same way.

Cool! Is this a P. bipinnatifidum?

I use soft wire to guide roots to the soil but if you wait too long to try they can break when you bend them.

The type of tissue the roots grow will change once it is underground, They'll start to branch and develop root hairs and as you've seen attach themselves to various media.

Plants don't seem to care one way or the other if you do anything with these roots although for taller plants they can provide water and nutrients to the upper portions of the vines.

Yes Greentoe,..it is. :)

Dellis, the root I stuck into the soil went in easily, but there is another growing more up than down (the one on the left in my original picture) - I might need to gradually train it parallel to the ground first, perhaps with asleep's straw trick or by otherwise gently weighing it down, before sticking it into the mix.

Asleep, I offered a friend to divide her bipinnatifidum when she mentioned her parents never had luck rooting leaves. It's looooooong overdue for a repot. If the plant seems divisible into three rather than two when unpotted, I might get one out of there for myself. Any advice when repotting/dividing? If we do this, it'll be next spring/summer.

With the promise of a bip division I'd wanna do it now(not sure if that's advisable or not but hey).

Get some shots of the trunk/trunks where they meet the soil...it may give us an idea of what we are working with here.

That's a nice plant!

You can't start a bipinnatifidum from leaves, You'll need to have a pup or branch to start it out, better yet is a pup with a few roots, either aerial roots or soil roots.

>> I'd wanna do it now

Yeah, I am itching too, but isn't it kind of late in the summer to do that? I would want the divided plants to grow a little bit in their new environments before the colder season sets in here. Two of the three divided plants will be living indoors all year long. The mommy plant is outside now in full sun for part of the day. I would think my friend needs to move it to full shade for a week or two before repotting/dividing in order for the change to be less drastic. So, I am afraid there is not enough time in the season.

>> Get some shots of the trunk/trunks where they meet the soil.

Cannot do, unfortunately - cannot even see them easily. The plant is sitting low in this tall planter. The pot is full of leaf petioles and aerial roots. There must be very little medium in there - cannot see that far. The trunk(s) must be short.

Also visible in the picture are many aerial roots lying on the stone floor that gets very hot during sunny summer days. How she keeps it watered is also a mystery - maybe that is why the leaves are a bit yellow.

The plant is definitely a survivor. She has had it for well over 10 years. It lives inside during the winters.

>> You can't start a bipinnatifidum from leaves.

Yeah, I told her that after I read up on this.

Hmmm...
Would it be possible the to pull it out of the pot so we could see the rootball and inspect for pups?

There's still a lot of warm, or at least, not cold weather this year. You do not need to wait. Keep them out of direct sun.

Any division of P. bipinnatifidum has to be done with roots. Never cut off a pup or part of a plant without roots. They belong to a different group that don't grow from cuttings like a lot of the other Philos.

Self header types have far shorter internodes(spaces between nodes)when compared to the vining types. I've had the trunk rot out from underneath a bip before and cut the roots to a tripod kinda thing and re-rooted it in water then graduated to soil...a nugget with leaves standing on aerial root stilts. Looked really cool.

Speaking of aerial roots...I do believe these guys need some straws

Annnnnd the flipside...

My friend seems only luke-warm on the idea of dividing her Bipinnatifidum. It may still happen, but I am letting it go for now. Easier to buy a plant and not risk me killing hers or whatever. I've seen them for $30 here - or maybe even better I can get one shaped similarly but with smaller leaves (Philodendron Xanadu I think it's called). I do have only indoor space.

Thanks to all for the advice.

Asleep, your plant is amazing. Looks very strong.

Thank you Greentoe!

I actually have two of them...the last one I shared was the larger of the two(in the green container).

If it keeps getting cold like it has been lately I may have to take my xanadu back inside with the other two divisions(which lack the woody trunk).

Another view...

And one more...

This last plant in the three pictures is planted kind of high, On purpose so that the roots show more?

Mornin!

You saw the "trunks" on the bips higher up in the thread,right? The xanadu does the same thing in miniature(albeit faster)...so nope...not planted higher...just the natural habit of a xanadu given enough time. There are crispy spent remains of older leaves at the bottom right now(didn't clean up before photo)and that may be what's looking like roots,but in time,I suspect there WILL be a bunch of aerials all over the place as eventually I will be doing the same thing I'm doing with my bips(training them to the soil)...after it rooted,..at the top, the new growth took the form of two separate crowns ...and one of them had aerial nubs beginning to show so I gently snapped that one off and set in in the terrarium. It took too! :)

...Months later and it's doing this feeling around looking for something to grab onto thing . Apparently it found the terrarium floor and started to do something else.

Put the naughty thing back in with the rest of the litter. :)

got it, Aleep.