When a cutting is taken from a parent plant, it severs the plant’s lifeline. The resulting “drooping” or wilting is the immediate, visible reaction to this trauma, caused by a loss of turgor pressure. Turgor pressure keeps plant cells firm and rigid, maintained by water uptake through the roots. Since a fresh clone has no roots, its ability to replace water lost through its leaves (transpiration) is severely compromised. The goal is to manage the clone’s environment to minimize water loss until a new root system develops.
The Immediate Environmental Stressors
The most urgent issue for a newly cut clone is the rapid loss of moisture to the surrounding air, a process called transpiration. To combat this, the clone needs a high-humidity environment to slow the rate of water evaporation from its leaves. Many growers use a humidity dome or chamber to create a microclimate.
Initially, maintaining a relative humidity (RH) between 75% and 90% is beneficial for the first seven to ten days. This high moisture level allows the cutting to absorb water directly through its leaf surface, effectively acting as a temporary root system. If the air is too dry, the clone will quickly dehydrate, causing the leaves to wilt and the stem to collapse.
While high humidity is necessary, air movement must also be managed carefully. Stagnant, moist air is an ideal breeding ground for mold, mildew, and fungal pathogens that can rapidly kill a vulnerable cutting. Gentle air circulation, such as a small fan blowing across the top of the dome, helps strengthen the stems and prevents the build-up of moisture on the leaf surface. As roots begin to form, the humidity should be gradually reduced by venting the dome, which helps “harden off” the plant.
Temperature and Light Intensity Imbalances
Temperature plays a dual role in the health of a clone, affecting both its rate of water loss and its metabolic speed. An ambient temperature range between 70°F and 78°F promotes root development. Temperatures that climb too high, especially above 80°F, accelerate transpiration, forcing the plant to lose water faster than it can absorb it and leading to rapid wilting.
Conversely, temperatures that are too low dramatically slow the plant’s metabolism and delay the rooting process. Maintaining a stable temperature is more important than achieving a specific number, as fluctuations stress the cutting. Many growers use a seedling heat mat to warm the rooting zone, which stimulates cell division and root growth without overheating the plant canopy.
Light requirements for clones are significantly lower than for mature plants. High-intensity light provides too much energy for an unrooted cutting to process efficiently, as it cannot transport nutrients without a root system. Exposing fresh clones to bright light increases leaf temperature, spiking the rate of transpiration and causing severe stress or “light shock.” Clones thrive under low-intensity, indirect light, such as T5 fluorescent fixtures or dimmed LED lights, with a light intensity often recommended to be in the range of 150 to 300 Photosynthetic Photon Flux Density (PPFD).
Substrate Saturation and Root Zone Health
The medium used to hold the cutting must provide a balance of moisture retention and oxygen availability to the forming root tissue. Oversaturation of the rooting medium is a common cause of drooping often misdiagnosed as dehydration. When the medium is too wet, air pockets fill with water, which deprives the developing cells of the oxygen they need to respire and grow.
This lack of oxygen creates an anaerobic environment that fosters the growth of harmful bacteria and fungi, leading to root rot. Root rot presents with symptoms similar to wilting, but the stem base or roots appear brown, soft, or slimy. To avoid this, the medium, whether rockwool, peat, or coco coir, should be moist but never soggy.
Proper drainage is essential to prevent water from pooling around the stem base. The best practice is to fully hydrate the rooting medium once and then allow the environment, such as the humidity dome, to manage the moisture. Placing the clone tray on a heating mat warms the base of the medium to around 75°F, which encourages root development while slightly increasing evaporation to prevent waterlogging.