Seed germination temperatures

The germination of seeds is easy, you put them in a good growing medium and off they go. Given the right conditions and germination temperatures any viable seed will grow but what are the right conditions? Sometimes you’ll need to stratify the seeds or you’ll need to scarify or damage the seed coat to give them a helping hand. Mostly though we’re just wanting to get some tomatoes or annual flowers growing and to make sure that they start as soon as possible have the best start here is a little guide to the process, terminology and some examples for common seeds. Germination can be considered as the point the the radicle begins to appear from the seed or when the cotyledon leaves emerge in angiosperms, either way you know when it happened as you see the first signs of growth.

What’s happening to make the seed germinate?

Rather than duplicate what I’ve written already here is a series of posts all about the subject. If you don’t want to read it all the a brief summary is:

Seeds are said to be dormant until the point that they start to germinate and to break that dormancy sometimes you need to chill, heat, or even break the casing a little called scarification. Environmental variables like fires or severe cold can be required for some seeds to break dormancy in their natural locations, these conditions are usually fairly easily replicated by us though.

What are all these terms about?


This is the process of cold treatment that some seeds need to break their dormancy and begin the process of germination. Sometimes it can require extreme cold below zero degrees C and other times it can simply be a few weeks just above. Often a few weeks in a refrigerator is enough to get them going.


Often with hard shelled seeds there can be a problem getting moisture in side to start the germinating process. Scarification is basically damaging the seed coat to allow the water in, this could be mechanical where the testa is physically opened up or just abrasing it with a knife or sandpaper. Sweet peas are a common example where this can help although I’ve never found the need.

Give me some examples

Temperature is hugely important when it comes to starting seeds off. If they don’t have the right heat (or cold) then they simply won’t get going. If the ground is wet then you’ll be likely to lose the seed altogether due to it rotting. A heated propagator is an ideal way to help with this or simply wait until the weather warms up and let nature do it’s thing. Here are some common examples anyway so that you can get an idea about what you’ll need to be doing to get you seeds germinating when you want them to, for everything else there should be information on seed packets, or ask and I’ll find out.

Germination temperature chart

2 thoughts on “Seed germination temperatures

  1. Ali

    This is so useful! Not aimless at all!

    1. Tim

      Thank you Ali, that diagram took me ages to make 🙂

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