I have a flowerbed that contains several well established Philodendrons planted by a previous owner. However they are growing somewhat larger than I wish to have in this location. Many of them have multiple stems and most are so heavy they are falling over. Combine that with the abundance of aerial roots, it is somewhat messy. Is there any preferred method to trim them back? Can I safely trim the aerial roots?
Your plant appears to be Philodendron bipinnatifidum which is often called Philodendron selloum by collectors. Both names were accepted scientifically until 1990 when Philodendron expert aroid botanist Simon Mayo of the Royal Botanic Gardens, Kew in England documented both "species" were actually a single species with multiple growth forms. The two had been differentiated previously since they were only slightly different due to natural variation. Many plants differ somewhat in their appearance but that does not necessarily mean they are unique species. You can find an explanation of natural variation near the top of this page. Your plants are members of Philodendron section Meconostigma which are known as "tree Philodendron" species. Most all are from Brazil. It is not uncommon for Philodendron bipinnatifidum to lay over and grow horizontally but in most cases it will again turn to grow upwards. This species is a bit difficult to "cut". You can top the existing plant so long as you keep enough of the aerial roots to replant it elsewhere. If you wish to cut the entire stem which is the portion that make the Philodendron resemble a "tree" a new plant will eventually grow from the roots that are in the ground. With any luck you can place the stem section you have removed and plant it elsewhere or simply lay it on loose soil and cover at least half in soil. I once had a grower give us a large number of stem sections and we cut them into 2 foot chunks and started an entire bed of the plants. The section left in the ground and the replanted sections should produce new plants in time. You can cut back the roots without a great deal of damage but they will always grow back. If planted near a tree the species will climb and I've personally seen them in South Florida growing well up into the canopy. In the rain forest Meconostigma species often climb trees. This link may give you more information. http://www.exoticrainforest.com/Philodendron bipinnatifidum pc.html
