The Q&A Archives: Germination Temperatures

Question: Can you tell me what the approximate minimum, optimum, and maximum temps. are for tomato and pansy seed germination?

Also, I've heard that light slows germination. If that's true, why?

Answer: Seeds contain an embryo capable of growing into a plant if all the requirements are met. For some seeds, this means total darkness and for others it means light is necessary for germination. Not all seeds have the same requirements, so it's important to follow the sowing directions on each seed packet. If the directions say sow on the surface of the soil, it means that particular seed needs light to germinate. If the directions give a depth to plant, that means that particular seed needs darkness to germinate. If you do not provide the right circumstances, seeds will fail to germinate, or will be slow in germinating because its needs are not being met.

Neither tomato or pansy seeds require light to germinate. Tomatoes are warm-season plants from tropical regions. Their seeds best at soil temperatures of 75F-90F. Once the first set of true leaves appear on the seedlings, the plants can be kept at temperatures of 60F-70F to prevent legginess. Pansy seeds will germinate in 10-21 days when soil temperatures are between 65F and 75F degrees. These seeds germinate best when refrigerated for 8-10 weeks before sowing indoors, or when sown outdoors, do so in autumn or very early spring so the seeds experience a chill prior to the soil warming up to germinating temperature.

Hope this answers your question!

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