A humidity box, frequently called a propagation chamber, is a contained environment created to maintain a high level of atmospheric moisture around plants. This enclosed space is particularly useful for rooting plant cuttings that lack the ability to draw water efficiently through roots, as high humidity prevents the cutting from drying out. The chamber also supports tropical houseplants that naturally thrive in environments with relative humidity levels often exceeding 75%. By trapping moisture released through transpiration and evaporation, the box creates a microclimate that reduces water loss from the leaves, fostering faster development and survival.
Gathering the Necessary Supplies
The construction of an effective humidity chamber begins with selecting the proper components. You will need a clear container, which serves as the walls and lid of your box. The container must be transparent to allow light to reach the plants inside, with options ranging from a clear plastic storage tote to an old aquarium or a large glass jar for smaller setups.
A moisture-retaining material is also required to hold water and increase the surface area for evaporation; suitable choices include perlite, coarse gravel, or sphagnum moss. This material should be placed in a separate, shallow tray or directly on the bottom of the main container, creating a pebble tray effect.
Finally, a thermometer and hygrometer combination tool is important for monitoring the interior conditions. The success of the box depends on knowing the exact temperature and humidity levels.
Assembling the Humidity Chamber
The assembly process focuses on establishing a sealed environment and a stable moisture source. Begin by ensuring your clear container is clean and that the lid fits securely to minimize air exchange. If the container is not naturally airtight, use weatherstrip seal or duct tape around the edges to improve the seal.
Next, prepare the base layer by adding your chosen substrate to the bottom of the container or a separate tray placed inside. If using perlite or moss, saturate the material until it is thoroughly damp, but avoid creating a standing pool of water that could submerge the bottoms of plant pots. The substrate acts as a wick, slowly releasing moisture into the air through evaporation.
If using a separate pebble tray, fill the tray with clean pebbles or gravel and add water until the level is just below the top surface of the stones. This prevents the base of the plant pots from sitting directly in water, which could lead to waterlogging and root rot. Place your potted plants directly onto this moisture layer, ensuring drainage holes rest above the water line. Position the monitoring tool inside the chamber, away from the direct water source, so it accurately reflects the air conditions surrounding the foliage.
Regulating and Maintaining Optimal Conditions
After assembling the box, continuous regulation is necessary to prevent issues like fungal growth and heat stress. The goal is to maintain relative humidity of at least 80% for propagation and between 65% and 80% for established tropical plants. Air temperatures should ideally remain between 64°F and 75°F (18°C and 24°C) to support healthy growth.
The placement of the humidity box dictates the internal temperature, so position it in an area that receives bright, indirect light. Direct, intense sunlight can rapidly increase the internal temperature, stressing and potentially cooking the plants inside. If temperatures are consistently too low, a heating mat placed beneath the container can help maintain the growing medium temperature, which benefits root development.
Ventilation, or air exchange, is a fundamental maintenance task that prevents the air from becoming stagnant and overly saturated, which encourages the growth of mold, fungus, or damping off disease. Open the lid or dome for a short period (15 to 60 minutes) at least once every few days to allow for air circulation. This action replenishes the carbon dioxide supply and cycles out stale, overly humid air, which is essential for ongoing plant respiration and health. As water evaporates, check the moisture reservoir and replenish it as needed to sustain the high humidity, often requiring a refill every few days to a week.