The following are some terms we use to talk about the type of light a plant will tolerate, and what we mean by them. When judging your natural light remember to do it will all of your lights turned off. Unless your lights are full-spectrum and made specifically for plants their effect is negligible.
Direct Sun: A sightline between the plant and the sun itself, typically within a few feet of a window and for at least a few hours of the day.
Some Direct Sun: Direct sun, but limited by obstructions like trees, blinds, or buildings.
Strong Indirect Light: Bright enough to read very comfortably without any lights, but no direct sightline between the plant and the sun.
Low Indirect Light: Bright enough to read but your eyes may strain
Low Light: Poorly lit, often far from a window or partially blocked.
Finding the appropriate plant for the light in your home can be one of the most challenging parts of houseplant care. All plants have a range of light that they’ll tolerate: at the upper end of their range they will show stronger growth and require more water to stay healthy, while at the lower end they may survive but not thrive. Your light is determined by the 3 Ds: direction, duration, and distance.
Direction The direction of a window affects the intensity of your light. A window facing due North might never get any direct sun, while one facing due South will get the most hours of intense direct sun. East and West windows receive the same amount of light, but the rising Eastern sun is gentler and cooler than the setting Western sun, which generates more heat and is more intense.
Duration Duration is determined by the blockages as well as the direction of your window and time of year.. The most common blockages are trees and buildings. Evergreen trees provide the same shade throughout the year while deciduous trees may filter light in the summer but not in the winter after they’ve lost their leaves. Even the location on the windowsill can have a drastic affect on the amount of light a plant receives throughout the day. The duration will also lessen or lengthen as we approach the winter and summer solstices, respectively. Watch your plants throughout the year, and don’t be afraid of adjusting their position to get them the light they prefer (apart from some of the ones that are more sensitive to being moved, like ficuses). A plant that has been comfortable all winter may begin to burn in August, when it’s getting more hours of sunlight, at an angle that is more intense (and vice versa).
Distance The intensity of light decreases exponentially as you move away from windows, and so a plant that is only a few feet from a window may show much different growth than if it were on the windowsill. A plant on the sill of an unobstructed window facing East may receive very strong indirect light and some direct sun, but eight feet away the light may only be considered weak indirect. Plants under skylights may receive a lot of “direct sun” but because the glass is usually 10-20 feet away the light may functionally be considered “strong indirect.”