I have repotted this plant several times. I now wonder if I should in fact divide it before I repot again. I am uncertain if this would be a good idea. If it is would you please tell me the best way to do this. I have had this plant for about 40 years. It’s become a family heirloom.
It’s not clear from the photo whether this is a philodendron or a Swiss Cheese plant (Monstera deliciosa). I suggest that you have the plant positively identified before proceeding, although both can be repotted and/or divided.
If it’s a philodendron
From your photo, this could be a non-climbing philodendron, possibly a tree philodendron (Philodendron bipinnatifidum), which can grow very large, i.e., up to 4 meters (13 feet) in 20 years. You can simply repot the plant, as you have done in the past. Remember that the roots are happiest when slightly cramped so do not select a new pot that is too large – use one that is a couple of inches larger than its current pot.
Alternatively, you can divide it. Just unpot the plant and using a sharp knife, cut its root mass into sections, making sure that each section has a stem attached to it. Plant each division into new pots of fresh potting soil.
Or is it Monstera deliciosa?
This could also be a Monstera deliciosa (hurricane plant, Swiss cheese plant – also incorrectly referred to as split-leaf philodendron). As it gets older, new leaves look like Swiss cheese – i.e., there are “holes” in the leaves – I can’t tell from your photo if this is the case with your plant. Monstera is usually repotted but can also be divided – see SFGate’s How to Divide the Root Ball on a Split Leaf Philodendron – briefly, water the plant thoroughly a week before dividing it, then not again until you have repotted it. Unpot the plant and put it on its side. Look at the crown of the plant to find natural divisions – this is where the plant should be divided. Using a sharp knife, slice from the crown to the bottom of the root ball, making sure that each section includes a portion of the crown and roots. Pot each division.