Grass does grow at night, and its physical expansion often accelerates significantly after the sun goes down. This growth is not a constant, steady process but rather a precisely timed biological event driven by the plant’s internal clock. Growth refers to the permanent increase in size, achieved through cell division (increasing cell number) and cell elongation (increasing individual size). This nocturnal activity depends entirely on the energy produced during the day, establishing a cycle of production followed by utilization.
Energy Production During the Day
During daylight hours, the grass leaf blades act as tiny solar panels, capturing light energy to fuel photosynthesis. This mechanism converts carbon dioxide and water into glucose, a simple sugar that serves as the plant’s primary source of chemical energy. The grass plant is highly efficient, typically producing more glucose than it needs for immediate energy demands and maintenance.
This excess sugar is converted into complex carbohydrates, which are stored within the plant’s tissues, particularly in the leaf sheaths and the crown near the soil line. This storage phase dominates the daytime cycle and is analogous to charging a battery. While some growth occurs during the day, the plant’s main focus is on energy production and storage, setting the stage for later physical expansion.
The Mechanics of Nighttime Growth
Once the sun sets, the grass plant shifts from energy production to utilization, initiating the period of maximal physical expansion. The stored carbohydrates are rapidly broken down and transported throughout the plant via translocation. This movement of sugars from storage areas (sources) to the growing points (sinks) provides the essential building blocks and fuel for growth.
The primary mechanism for visible growth at night is cell elongation, where existing cells stretch and expand, increasing the blade’s length. This expansion is facilitated by turgor pressure, the internal force of water pushing against the cell walls, which is highest at night due to reduced water loss. With carbohydrate fuel delivered and turgor pressure maximized, many turfgrass species exhibit their fastest growth rates in the hours just before dawn.
How Temperature and Water Affect Growth Timing
The rate of nocturnal growth is heavily regulated by external environmental conditions, with temperature and water availability being the most influential factors. For cool-season turfgrasses, optimal shoot growth occurs when nighttime air temperatures are in the mid-50s Fahrenheit. Temperatures significantly above or below this range can inhibit the enzymatic activity required for cellular expansion and division.
Water plays a direct role in supporting the turgor pressure needed for cell elongation. During the cool, dark hours, the grass experiences dramatically reduced transpiration, the process of water evaporating from the leaves. This lower water stress allows the plant to maintain high water content, which is crucial for maximizing the physical stretching of cells. The presence of dew or high humidity further reduces moisture loss and ensures the plant’s internal pressure remains high.