Hardening off seedlings can be accomplished by all of the following except which?

• A. Lowering temperatures
• B. Decreasing relative humidity
• C. Giving less water
• D. Apply half-strength, high nitrogen fertilizer

Answer: (D)

Hardening off seedlings is about gradually acclimating indoor-grown plants to outdoor conditions so their tissues become tougher and more resilient. Lowering temperatures, reducing relative humidity, and giving less water all mimic the harsher outdoor environment and prompt the plant to strengthen stems, develop a sturdier cuticle, and extend roots to access limited moisture. In contrast, applying fertilizer that is high in nitrogen encourages rapid, lush, tender growth with softer leaves, which is the opposite of what you want during hardening off. This kind of growth is more vulnerable to sun exposure, wind, and drought once the seedlings are outside. So, high-nitrogen fertilizer is not part of the hardening-off process.