These plants are mostly native to tropical areas of South America, so many require at least 70% Humidity. Misting your plant frequently is a great way to succeed for beginner growers. However, low air movement can cause your plant to invite unwelcomed guests like diseases, pests, and fungi. Indoor growing should be done in a room with good air circulation, which can be provided by pointing a fan at your plants or placing them near a screened window. With lower air circulation, you have to really tease your philodendron by watering more often with lower quantities of water.
Even in a lower-air movement environment, your philodendron will appreciate daily misting on the leaves and aerial roots. Aerial roots are the roots that grow out of each node (the swollen section where new leaves, growths, and roots can grow from the vine). Outdoor growing can be a little bit different, as the heat, wind, and dryness can cause your plant's soil to dry out very quickly. You will have to give your plant more thorough waterings when it is being exposed to the same kind of conditions that would make you sweat and want to drink more water as well. When it is hot outside, getting the leaves of your plant wet helps cool it down.
Another factor to consider is how much rain you are getting each day, as your plant needs its soil to dry out a little in between each watering. This issue can be avoided by repotting your plant into a fast-draining mix like orchid bark, perlite, and coconut coir. You will have to water much more often with outdoor mixes, so keep that in mind when determining where to grow your philodendron. Growing outdoors in shady areas will reduce the water intake, and growing under a solid covering will allow you to protect your plant from being overwatered.
Provide medium to bright indirect sunlight, as the full sun will either be too hot or too bright for most varieties of philodendrons. When your plant is not getting enough light, the leaves will turn dark green and each new leaf will become smaller than the last one. Conversely, too much light will cause your plant's leaves to lighten up and become discolored.
If your plant is only having issues with its lower leaves, then it is most likely a result of improper watering, bacterial root rot, or nutrient deficiencies. Grow lights will always be beneficial to indoor plants, and will allow you to grow your philodendron in areas that receive less natural light. Most grow lights have a built-in timer, so you can give your plants a consistent lighting schedule. Unless you are using a higher-strength grow light, your plants will need to be within a few feet to benefit from the artificial exposure.
Philodendrons are usually found growing in South American tropical forests, swamps, river banks, and along rocky outcroppings. The temperature of their habitats generally stays between sixty to ninety degrees Fahrenheit, but seventy to eighty-five degrees Fahrenheit would be the optimal growing temperature.
Fertilize your philodendron with an all-purpose 20-20-20 fertilizer every two weeks during the spring and summertime, or once a week at half strength. During the Fall, fertilize once a month as the temperatures start to drop, and Fertilize once a month at half strength during the winter time.
Keep in mind that fertilization and watering may differ based on indoor growing conditions. If your plant is experiencing stress unrelated to nutrient deficiencies, you may want to avoid fertilization until your plant grows new leaves and roots. Giving your plant too much fertilizer can damage the roots and lead to bacterial root rot or fungal diseases.
This video includes a demonstration of the pollination of philodendron Red Emerald using Philodendron Verrucosum pollen.