I do not know what these are called. Also I Want to repot them and I need advice regarding the container size
Hello – I believe your plant is a split-leaf philodendron, also commonly called a tree philodendron or a horsehead philodendron. The botanical name is Philodendron bipinnatifidum. It is native to parts of South America where it can grow up to 15 feet tall. As an indoor container plant, it typically grows much smaller. If you’d like to read more about Philodendron bipinnatifidum, I’ve included a link below some information on this plant from the Missouri Botanical Garden.
When repotting any houseplant, it is recommended that you select a container that is no more than 2-4 inches in diameter larger than the current one. The reason for this is explained by Darryl Cheng in his book ‘The New Plant Parent’. The new soil that contains no plant roots will hold moisture longer than areas with lots of roots that are accessing the moisture. A consistently moist environment supports the growth of root-rot bacteria. While your plant is out of the pot, take the opportunity to check for any rotting roots (appear dark brown or black) and remove them and gently loosen the other roots to give them a head start in re-establishing in new soil. Good luck repotting your plant!