What Causes Indoor Plant Leaves to Sweat?

Anatomy of a Leaf

• The leaf is the primary food factory of the plant. This is where the process of photosynthesis takes place, using the substance chlorophyll that gives plants their green appearance. The leaf's outer surface, called a cuticle, prevents the leaf from water loss. The next layer is the epidermis, which holds the veins of the leaf. Inside the veins are the phloem and xylem, cells that transport sugars and fluids within the plant. The middle layer of cells in a leaf is called the mesophyll. It is in this layer that the chloroplasts hold the chlorophyll and that photosynthesis takes place. Indoor plants need to photosynthesize just as much as outdoor plants. That is why they need a source of light.

Photosynthesis and Transpiration

• Photosynthesis is how plants makes food. Plants draw water from the roots and carbon dioxide from the air and converts them to sugars and starches. Oxygen is created as a by-product. The carbon dioxide and oxygen enter and leave the plant through tiny structures called stoma. Water vapor escapes through the stoma in the related process of transpiration.

Humidity's Role

• If a room is really hot and humid, or if a plant takes in more water than it needs, the excess is released through the stoma. Since humid air is saturated with moisture, the excess water vapor condenses and collects on the leaves in what looks like plant sweat. You can control the excess water release by cutting back on the amount of water you give the plant. Opening a window or two, weather permitting, also will help. Fresh air circulating around the plant will help evaporate some of the moisture on the leaves.