Greenhouse Gardening

Watering

Watering is an ongoing challenge for school greenhouse growers. Water is the solvent that carries minerals from the soil to plants via the roots. A raw material used in photosynthesis, water enters the roots as a liquid and exits the leaves as a vapor as it's transpired.

"Students may learn something simple, as simple as how to water a plant," says Joyce Harris, a volunteer greenhouse manager at Langley School. "Not all plants have the same watering requirements."

The amount of water plants require is affected by the drainage capacity of the growing medium used, the temperature and light plants receive, the amount of air circulation, the stage of plant growth, and the type of plant. Young, actively growing seedlings, for instance, require constant moisture, while a mature cactus needs very little.

Over-watered plants are at just as much risk as those that are under-watered. (Sometimes over-watered plants wilt as their roots suffocate, leading us to think they need even more water!) Have students practice "reading" the plants by using a finger to check moisture levels. If the soil feels dry an inch down, it's time to water. Don't necessarily water out of habit or on a schedule; water when the plants need it.

Watering Tips

• Use slightly warm (65 to 80°F) water.
• Water in the morning to minimize evening condensation on leaves, which can encourage diseases.
• Minimize watering on cool, cloudy days.
• Be careful not to splash mud, damage seedlings, or get water on fuzzy-leaved plants.
• Be sure to water thoroughly. Watering too lightly can cause a buildup of fertilizer salts, which can be toxic to plants, and also stimulates shallow, surface roots at the expense of larger roots.

 

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