linguistic:paraphrasing
Propagation

New plants can be grown by taking stem cuttings with at least two joints. Cuttings then can be rooted in pots of sand and peat moss mixtures. These pots are placed in greenhouses with bottom heat of 21–24 °C. During the rooting, cuttings should be kept out of direct sunlight. Once rooted, the plants can be transplanted to larger pots or directly outside in milder climates. Stem cuttings, particularly from trailing varieties, can be rooted in water. In four to five weeks, the plant should develop roots and can be transferred to pots. Philodendrons can also propagate through air layering which is a more advanced method of propagation that involves creating a new plant on the stem of an existing plant.

Hybridizing philodendrons is quite easy if flowering plants are available, because they have very few barriers to prevent hybridization. However, some aspects of making crosses can make philodendron hybridization more difficult. Philodendrons often flower at different times and the time when the spathe opens up varies from plant to plant. The pollen and the inflorescence both have short lives, which means a large collection of philodendrons is necessary if crossbreeding is to be done successfully. The pollen life can be extended to a few weeks by storing it in film canisters in a refrigerator. Artificial pollination is usually achieved by first mixing the pollen with water. A window is then cut into the spathe and the water-pollen mixture is rubbed on the fertile female flowers. The entire spathe is then covered in a plastic bag so the water–pollen mixture does not dry out; the bag is removed a few days later. If the inflorescence has not been fertilized, it will fall off, usually within a few weeks.