You might have sown your seeds for a while now, and you are getting impatient. Why haven’t your seeds given any signs of life yet? Perhaps it is just too early. How long should you wait?
Seeds germination time varies from 4 days to as long as several months. The optimal temperature range for germination was found to be between 60 and 68F (15 and 20C) for the majority of herbs, plants, and vegetables. For many plants, the minimum germination time was found to be 50F (10C).
These germination times are extremely important. However, nothing is written on stones. Indeed, they greatly vary with temperature and moisture conditions. Let’s see what science says.
I am a fan of culinary herbs. They grow fast, and you do not need great care to thrive. Just avoid the 18 most common mistakes, and they will thrive in no time. Without forgetting that they will reward you with tasty leaves for many months (if not years as discussed in the how long herb last article).
The germination time changes dramatically depending on the plant considered. Basil and mint are among the fastest herbs to germinate with a minimum of just 3-4 days in the right conditions. Rosemary is one of the herbs with the highest germination time (2 weeks). The majority of herbs have an ideal germination temperature of 68F (20C) that guarantees the shortest germination time.
The chart below reports the average germination time at the optimal germination temperature found in dozens of studies and experiments for the 14 most common herbs and shrubs.
|Herb||Seed Germination Time||Seed Temperature Germination|
|Basil||4 to 10 days||77-86F (25-30C)|
|Holy Basil||4 to 14 days||86-95F (25-35C)|
|Cilantro||5 to 10 days||50-85F (10-29C)|
|Sage||7 to 20 days||86-95F (25-35C)|
|Rosemary||14 to 30 days||60-65F (15-18C)|
|Oregano||7 to 14 days||68-86F (20-30C)|
|Chives||14 to 20 days||59-68F (15-20C)|
|Cilantro||7 to 14 days||68-86F (20-30C)|
|Catnip||10 to 14 days||70 to 80F (21-27C)|
|Thyme||14 to 30 days||59-68F (15-20C)|
|Dill||10 to 14 days||55-60F (13-16C)|
|Lavender||21 to 90 days||55-65F (13-18C)|
|Lemon Balm||10 to 14 days||64-68F (18-20C)|
|Mint||5 to 14 days||70-75F (21-24C)|
Below you can find the optimal germination temperature and time for the majority of vegetables you might want to grow. In general, time is quite similar to herbs, varying from as little as 2 days to 2 months.
Lettuce is among the vegetables that germinate the quickest with only 2 days in the right conditions compared to the slower garlic that takes at least half a month in the right conditions.
Check the germination chart with time and optimal temperature for 14 vegetables below.
|Vegetable||Seed Germination Time||Seed Germination Temperature|
|Leeks||11 to 14 days||35-77F (2-25C)|
|Peppers||7 to 21 days||68-95F (20-35C)|
|Lettuce||2 to 12 days||60-75F (16-24C)|
|Tomatoes||4 to 10 days||68-95F (20-35C)|
|Cucumber||7 to 10 days||63-73F (17-23C)|
|Carrots||7 to 21 days||68-77F (20-25C)|
|Spinach||5 to 10 days||45-75F (7-24C)|
|Broccoli||10 to 14 days||60-85F (16-29C)|
|Beans||6 to 10 days||75-85F (24-29C)|
|Beetroot||10 to 14 days||50-85F (10-29C)|
|Onion||7 to 10 days||68-95F (20-35C)|
|Garlic||14 to 60 days||65-85F (18-29C)|
|Radishes||3 to 5 days||15-20C (59-68F)|
|Zucchini||7 to 14 days||70-95F (21-35C)|
Finally, here you can find the germination time and temperature for a large variety of many common flowers, fruits that you might be interested in. Here the time varies quite significantly from just 4 days of melon to up to 2 months of elephant ears.
Check below the germination chart for 19 common houseplants and flowers.
|Plant||Seed Germination Time||Temperature for Germination|
|Grass seed||Up to a month||41-86F (5-30C) depending on the grass type|
|Apricot||Up to 2 months||59-187F (15-20C)|
|Asparagus||Up to 3 weeks||75-85F (24-30C)|
|Squash||Up to 10 days||85-95F (29-35C)|
|Amaranth||Up to 10 days||70-75F (21-24C)|
|Beets||Up to 12 days||65-85F (18-29C)|
|Cauliflower||Up to 10 days||65-85F (18-29C)|
|Avocado||Up to 1.5 months||70-81F (21-27C)|
|Daisy||Up to 3 weeks||20-25C (68-77C)|
|Eggplant||Up to 2 weeks||80-90F (27-32C)|
|Elephant Ears||Up to 2 months||>50F (10C)|
|Melon||Up to 10 days||75-95F (24-35C)|
|Fescue||Up to 14 days||70-80F (21-27C)|
|Nasturtiums||Up to 12 days||65F (18C)|
|Nicotiana||10 to 22 days||70-75F (21-24C)|
|Okra||Up to 14 days||85-95F (29-35C)|
|Pumpkin||Up to 10 days||85-95F (29-35C)|
|Poppy||Up to 22 days||55-60F (12-16C)|
|Zinnia||Up to 7 days||8085F (2729C)|
Temperature heavily affects seed germination time and rate of success. Indeed, seeds germinate when the “environmental conditions” are just right. Often this means the arrival of springs/summer as long hours of sunlight and milder temperature imply better-growing conditions. This explains why the majority of herbs and vegetable seeds require relatively 1) stable and 2) high temperature to sprout.
All vegetables and herbs seeds sprout easily for temperatures of around 68F (20C) or slightly above.
Herbs and plants do not have a single specific temperature at which they sprout. They are able to germinate within a given temperature range (the one I provided in the tables above). For instance, in the first table (herbs), basil has an ideal germination temperature range of 25-30C (77 to 86F). Hence, basil seeds can germinate fast and with a high rate (most of the seeds will sprout) in such a temperature range.
Does that mean that any temperature outside the ideal germination temperature range (tables above) will not sprout? No, these are ideal temperatures for which your herbs will grow the fastest and higher germination rate. For instance, as discussed by the Virginia Polytechnic, sweet basil can grow with any temperature between 50 to 104F (10 and 40C) (let’s call it “possible temperature range”). This is wider than the ideal temperature range of 77 to 86F (25-30C).
Some exceptions, as discussed by the Oregon State University, are the cold-germination crops. Indeed some of the most common vegetables like broccoli, cabbage, carrot, cauliflower, radish can germinate with as little as 40F (4C) while others like lettuce, onion, parsnip, and spinach w even at low as 35°F (2C).
Remember also that, sometimes, there is a small genetic component. You might provide the best conditions, but because of some variation or even some seed disease, some might not sprout or die straightener. It happened to me a couple of times. However, if you have purchased seeds from reliable vendors, this should not be a problem.
Where to find good quality seeds?
For herbs seeds, I usually opt for the Sow Righ Seeds brand. You can check them on Amazon here. Never had problems, and their germination rate is quite high. For the UK audience, the De Ree is also a great option.
How to keep the temperature constant during germination?
To guarantee the right temperature, I would go for a seedling bed mat. It is essentially a small resistor (that consumes like a lamp) that provides constant heat for your seeds. You just need to plug them and place beneath the seedlings pot. Check this good one on Amazon to see how they look like.
Will seed germinate in cold weather? Some vegetable seeds such as lettuce, given the right moisture conditions, can germinate in cold weather (as low as 35F). However, this is not the case for herbs seeds.
Do seeds need heat to germinate? The large majority of herb and vegetable seeds, except a few exceptions (the so-called cool-season crops) do require heat that guarantees a sufficiently high temperature in the growing medium where the seeds are placed. This can be either from natural resources or natural.
This article would not have been possible without the scientific contribution of biologists and other researchers all over the world performing cool experiments to find out for us the best conditions possible for growing our seeds.
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