Establish the Perfect Growing Conditions

March 31, 2021

Establish the Perfect Growing Conditions

2 minute read

April is the ideal month to plan which vegetables and herbs you’re going to grow. To give your seeds the best chance of germinating and eventually producing an abundant harvest, it’s important to get the growing conditions right from the very start. There is also still the chance of frost at night which will need to be monitored. Most vegetables and herbs will need to be sown indoors or undercover, and kept there until all risk of frost has passed.

Three factors that can be monitored to ensure optimal germination and growing conditions are soil temperature, air temperature and humidity.

Soil Temperature

The ideal soil temperature will vary depending on what you’re growing, so it’s a good idea to check beforehand. In general, most seeds won’t germinate if the soil temperature is below 7°C. To determine the soil temperature and ensure readings are accurate, use a good quality soil thermometer. We suggest a measuring depth of around 2 inches and to record the temperature twice a day.

Air Temperature

It’s important to remember that the air temperature will likely be different to the soil temperature, whether it’s indoors or in a greenhouse. A temperature of 18-21°C will be ideal for growing most vegetables and herbs. Monitor the temperature of all growing locations. Use a weather station with multiple sensors to keep track of each area and note the minimum and maximum readings. Once the night temperature is regularly reaching 7°C, seedlings can start to go outside.


Monitor the humidity levels of your growing spaces throughout the season, whether it’s indoors or outdoors. Seeds will need moisture to germinate, so using a propagator will ensure that humidity levels are high enough. However, if seedlings are kept in too humid conditions, it can cause rot or mold problems, which is why it’s important to actively monitor levels. Use a humidity sensor for smaller areas such as propagators, or a hygrometer dial for a greenhouse or outside.

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Frequently Asked Questions (FAQs)

1. What is the best soil temperature for germinating seeds? The ideal soil temperature for seed germination varies depending on the type of vegetable or herb you are growing. Generally, most seeds require a soil temperature of at least 7°C to germinate effectively. Check specific requirements for each type of seed for the best results.

2. How can I accurately measure soil temperature? To accurately measure soil temperature, use a high-quality soil thermometer. Insert it about 2 inches deep into the soil and record the temperature twice daily, once in the morning and once in the evening.

3. What should the air temperature be inside a greenhouse? For optimal growth of most vegetables and herbs, maintain an air temperature between 18-21°C inside a greenhouse or indoors. Regular monitoring with a weather station equipped with multiple sensors can help ensure these conditions.

4. How do I know when to move my seedlings outdoors? Seedlings can be moved outdoors once the nighttime air temperature consistently stays above 7°C. It’s important to acclimate seedlings to outside conditions gradually to prevent shock.

5. How can I maintain the right humidity for my seedlings? Maintain high humidity for seed germination by using a propagator. For ongoing care, monitor the humidity with a sensor in small areas or a hygrometer in larger spaces like greenhouses. Adjust ventilation as needed to prevent issues like rot or mold.

6. What should I do if my seedlings start showing signs of mold or rot? If seedlings show signs of mold or rot, reduce humidity by improving air circulation and possibly lowering the ambient moisture levels. Check your watering schedule and make sure the soil is not waterlogged.

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