The glasshouse door

An original fiction passage set in the nineteenth century.

Julia entered the glasshouse and found the plants covered with cloths. Her grandfather had feared the frost. He moved from pot to pot, checking the leaves as tenderly as a nurse visiting patients. Julia offered to carry more blankets from the house. He accepted, then reminded her to shut the door behind her. Outside, the lawn shone white in the morning light. Inside, the air remained almost warm.

Identify the phrase which compares the grandfather’s care for plants with care for people.