Best Soil Temperatures For Sowing Flower & Herb Seeds

This chart lists the optimum soil temperatures for starting flower and herb seeds. We’re often told seeds need warmth to sprout but you can overdo it. Find out what your seeds need to achieve the best germination rates.

Growing vegetables? This lists the recommended temperatures for starting vegetable seeds.

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Why Soil Temperature Matters

No matter what type of flower or herb you are starting from seed, the basic needs are the same.

Water, air, and warmth.

When a seed is introduced to these things in the right way, the embryo inside the seed breaks dormancy and starts to grow.

The warmth part, or, more specifically, the temperature of the soil (potting mix, seedling mix) when germinating the seeds, can make a big difference.

Too low and the seed may not grow or will grow much slower than anticipated.

Too warm and the seed may sprout but die off.

In the sweet spot—the recommended soil temperature range—along with adequate water and air, the seed grows into a seedling as quickly and efficiently as possible.

The twist in all of this is each plant species has its own preferred soil temperature range.

As you’ll see from the chart below, some seeds need cooler conditions than others.

While it is completely unrealistic to cater to all of these different needs, you can give your seed- starting a boost by grouping seeds with similar needs together.

And, if you have ever struggled with any one particular type of seed, maybe that’s the one that does get special treatment.

Starting indoors, this could mean using a seed starting heat mat with a thermostat, ensuring that the potting mix stays in the best temperature range for the duration of germination. You can also use a standard digital kitchen thermometer to check soil temperatures. There are more tips here for how and when to use a heat mat.

Then, with your seeds sprouted, lower the temperature by about 5-degrees. Seeds need warmer temperatures to sprout than they do to grow.

Flower & Herb Seed Starting Temperature Chart

This chart lists recommended soil temperatures only. Check your seed packet for any recommended pre-treatments like scarification, stratification, or pre-soaking prior to sowing.

Before adding any plants to your garden, be sure they are non-invasive and suited to your growing region.

I’ve done my best to find reliable sources for this information but different varieties may have slightly different preferences. Just do what you can to be as close to mid-range as possible and the seeds will do the rest.

For an indoor seed starting plan, see 30 Flower Seeds To Start Indoors.

This has more on direct sowing outdoors before last frost.

I hope this helps improve your seed starting efforts. If you enjoy tips like this, be sure to sign up for the free Empress of Dirt Newsletter (every two weeks).

~Melissa the Empress of Dirt ♛