Third Reality Zigbee Plant Monitor Review

Do you have a habit of killing plants? Do you also run Home Assistant? If you answered yes to both questions the Third Reality soil moisture sensor might be exactly what you need. Using the Zigbee protocol this sensor will keep an eye on the growing conditions for your plant. I can’t promise your plant won’t die — but at least this time you’ll know why.

The top twists open to reveal the internals with a rubber seal to keep out moisture. The top is fiddly to open as there isn’t much to grab and twist. The long black probe feels too fragile to hold while twisting off the top. Thankfully, with the quoted 3 year battery life of the Single AA battery means it doesn’t need to be opened very often.

Using this larger battery along with a weatherproof casing does make it a bit bigger than originally expected, it may look slightly odd in a small plant pot with a small plant.

Pairing with Home Assistant

Using ZHA this was very easy to pair
1. Login to Home Assistant, select “Settings” in the left hand menu, select Integrations, select “Zigbee Home Automation” and finally press the blue “Add device” button. ZHA is now listening for a new device.
2. Unscrew the top green cover (careful not to grab the long black prong while twisting) and press the small black button inside. Device will appear after around 10 seconds

Sensors and Entities

Once paired you will see the following entities in Home Assistant, all pretty self explanatory

Automations

Now that you have the information in Home Assistant you can do whatever you want, just trigger your automation for when the soil starts to get dry.

I like to follow this up with a phone notification

The soil is at {{ states(‘sensor.plant_monitor_01_soil_moisture’) }}%. Time to water before the leaves go brown!

Dashboard Example

In case you need some inspiration, here is my dashboard view of the plant monitor.

type: horizontal-stack
cards:
  - type: vertical-stack
    cards:
      - type: custom:mushroom-title-card
        title: Earnie Monstera
      - type: picture
        image:
          media_content_id: media-source://image_upload/69eda64536b70c8c04980ad245677181
          media_content_type: image/png
          metadata:
            title: Monstera.png
            thumbnail: /api/image/serve/69eda64536b70c8c04980ad245677181/256x256
            media_class: image
            children_media_class: null
            navigateIds:
              - {}
              - media_content_type: app
                media_content_id: media-source://image_upload
      - type: custom:mushroom-template-card
        primary: >-
          {% set moisture = states('sensor.plant_monitor_01_soil_moisture') |
          float(0) %}

          {% if moisture > 75 %} Soil is too wet

          {% elif moisture > 25 %} Soil moisture level is good

          {% elif moisture <= 25 %} Soil is getting a little dry

          {% else %} Plant needs to be watered

          {% endif %}
        icon: >-
          {% set moisture = states('sensor.plant_monitor_01_soil_moisture') |
          float(0) %}

          {% if moisture > 75 %} mdi:water-alert

          {% elif moisture > 25 %} mdi:check-circle

          {% elif moisture <= 25 %} mdi:water-percent

          {% else %} mdi:water-pump

          {% endif %}
        entity: sensor.your_plant_moisture_sensor
        color: >-
          {% set moisture = states('sensor.plant_monitor_01_soil_moisture') |
          float(0) %}

          {% if moisture > 75 %} blue

          {% elif moisture > 25 %} green

          {% elif moisture <= 25 %} red

          {% else %} red

          {% endif %}
        features_position: bottom
      - type: custom:mini-graph-card
        entities:
          - entity: sensor.plant_monitor_01_soil_moisture
            name: Soil Moisture
        line_color: "#4caf50"
        show:
          icon: false
          labels: true
          points: true
        color_thresholds:
          - value: 0
            color: "#e74c3c"
          - value: 25
            color: "#e67e22"
          - value: 35
            color: "#4caf50"
          - value: 80
            color: "#3498db"
      - type: entities
        entities:
          - entity: sensor.plant_monitor_01_temperature
            name:
              type: entity
            secondary_info: last-updated
          - entity: sensor.plant_monitor_01_humidity
            name:
              type: entity
            secondary_info: last-updated
          - entity: sensor.plant_monitor_01_battery
            name: Sensor Battery Level
            secondary_info: last-updated
        show_header_toggle: false

Pros & Cons

Pros

• Excellent battery life (AA battery)
• Reliable Zigbee connection
• Easy pairing with ZHA
• Weather-resistant design

Cons

• Slightly bulky for small pots
• Fiddly battery access
• Pricier than DIY alternatives

Conclusion

I have had this sensor paired for a few weeks, it has never dropped off and provides regular updates.

If you want a reliable, low-maintenance soil sensor that integrates cleanly with Home Assistant, this is an easy recommendation. Unfortunately at £20 this isn’t the cheapest sensor. DIY ESPHome sensors or cheap Bluetooth probes are cheaper but this sensor from ThirdReality is far more ‘set and forget’

I was pleased to see that it had a large AA battery rather than a small button battery that needs replacing every few months.

The ThirdReality zigbee soil moisture sensor can be purchased from Amazon.