If you’re unsure of what a solstice or equinox is, a solstice (we have a Summer & Winter solstice) is when the sun meets the point on the horizon and stops and reverses in direction, resulting in a change in length of night and day. It is when the sun is at its greatest distance from the celestial equator. An equinox, is when the sun crosses and stays exactly above the celestial equator indicating that the hours of each night is of equal length.
The importance of understanding these solstices or equinoxes is that they change the relative hours of day and night. When daylight hours change it can certainly impact our plants response to growth. The duration and intensity of light increase during the Spring are more favorable for plant growth and their metabolic activity will start to speed up to promote more growth!
For city dwellers, if you live higher up, say, on the 22nd floor, you receive MUCH brighter light than a 1st or 3rd floor window would since your angle to the sun will be much closer and you’ll most likely have no obstructions. Be sure to consider window size, and obstructions indoors and outdoors that could be blocking your plants view of the sky.