# How do I set up my leaf temperature sensor?

Setting up the Leaf Temperature Sensor is quick and easy:

{% stepper %}
{% step %}
**Position it correctly**

Place the base of the sensor over a leaf as close to the top of the plant as possible (the leaf temperature sensor is on the bottom of the Grow Sensor). 
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{% step %}
**Monitor live data**

Once positioned, the sensor detects the leaf and provides real-time leaf temperature readings, along with a continuous leaf VPD reading - a direct insight into plant health, in the app.
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### The i**deal difference between leaf temperature and ambient temperature**

For optimal plant health, your leaf temperature should typically be 1-3°C (2-5°F) cooler than the ambient air temperature. This indicates that the plant is actively transpiring and cooling itself through evaporation.

If the leaf temperature is equal to or warmer than ambient temp, your plant may not be transpiring efficiently. This could be due to:

* Low humidity (causing stomata to close).
* Excessive light or heat stress.
* Insufficient airflow.
* If the leaf temperature is a lot lower than the ambient, your plant may be transpiring too aggressively, leading to excess water loss and potential nutrient issues.

{% hint style="info" %}
**Key Insight:** Adjust environmental factors like humidity, airflow, and light intensity to maintain the ideal leaf-to-air temperature difference for healthy transpiration and nutrient uptake.
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### **Leaf VPD Targets**

Live Leaf VPD (Vapor Pressure Deficit) is a game-changer for plant health and monitoring. It directly impacts how efficiently your plants transpire and uptake nutrients. 

**Here are the ideal Leaf VPD targets based on your feeding strategy:**

<details>

<summary><strong>High EC Feeding (3.0 EC+)</strong></summary>

* Early Flower (Weeks 1-3): 0.6 - 0.8 kPa
* Mid Flower (Weeks 4-6): 0.8 - 1.0 kPa
* Late Flower (Weeks 7-10+): 1.0 - 1.2 kPa

</details>

<details>

<summary><strong>Lower EC Feeding</strong></summary>

* Early Flower (Weeks 1-3): 0.7 - 0.9 kPa
* Mid Flower (Weeks 4-6): 0.9 - 1.1 kPa
* Late Flower (Weeks 7-10+): 1.1 - 1.3 kPa

</details>

{% hint style="info" %}
**Key Insight**: Lower EC feeding requires a slightly higher VPD target to encourage better nutrient uptake, while high EC feeding benefits from lower VPD to prevent over-transpiration and nutrient imbalances.
{% endhint %}

### W**hen NOT to Use the Leaf Temperature**

* **Young plants (1-3 weeks old)** – Placing the sensor on small leaves can block too much light, which may slow early development. Instead, position the Grow Sensor next to the plant until the leaves are large enough.
* **If leaves are too small to support the sensor** – Wait until the plant is established before using leaf temperature measurements.


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