Help with a binary sensor template to monitor plant moisture

I have been trying to create a binary template sensor to monitor if a plant needs after. Ultimately the binary sensor will trigger an alert.

I am having trouble getting the sensor to work

binary_sensor:
  - platform: template
    sensors:
      - monstera_deliciosa_moisture_low:
          value_template: {{state_attr('sensor.monstera_deliciosa','moisture')|float < 15.0 }}
          friendly_name: 'living room monstera deliciosa moisture is low'