There are several environmental conditions that influence seed germination in hydroponics: overall seed condition, the presence of water, the presence of oxygen, what type of growing medium you’re using, and temperature.
And out of all of these conditions, temperature seems to be the most difficult to get right when starting seeds. But why is that exactly?
Well, there are really only two reasons: (1) the temperature is out of your control because you’re planting outside, or (2) you’re planting inside and trying to start seeds outside of their optimal range.
With that being said, if you’re having some difficulty with the germination process, take a look at the chart(s) below and explore optimal temperature ranges and seed germination times for plants commonly grown in hydroponic systems.
Once you’re finished, explore our Seeds and Seedlings Guide and our Hydroponic Hobby Center to learn even more!
Germination Temperatures Needed for Hydroponic Plants
| Vegetable/Plant | Minimum Temperature (ºF) | Optimum Temperature Range (ºF) | Maximum Temperature (ºF) |
|---|---|---|---|
| Asparagus | 50 | 75-85 | 95 |
| Beans, Lima | 60 | 75-85 | 85 |
| Beans, Snap | 60 | 75-85 | 95 |
| Beets | 40 | 65-85 | 95 |
| Broccoli | 40 | 60-85 | 95 |
| Cabbage | 40 | 60-85 | 95 |
| Carrots | 40 | 65-85 | 95 |
| Cauliflower | 40 | 65-85 | 95 |
| Celery | 40 | – | – |
| Chard, Swiss | 40 | 65-85 | 95 |
| Corn | 50 | 65-95 | 105 |
| Cucumbers | 60 | 65-95 | 105 |
| Eggplant | 60 | 75-85 | 95 |
| Garlic | 32 | 65-85 | 95 |
| Leeks | 32 | 65-85 | 95 |
| Lettuce | 32 | 60-75 | 85 |
| Muskmelons (Cantaloupe) | 60 | 75-85 | 105 |
| Okra | 60 | 85-95 | 105 |
| Onions | 32 | 65-85 | 95 |
| Parsley | 40 | 65-85 | 95 |
| Parsnips | 32 | 65-75 | 85 |
| Peas | 40 | 65-75 | 85 |
| Peppers | 60 | 65-75 | 95 |
| Pumpkins | 60 | 85-95 | 105 |
| Radishes | 40 | 65-85 | 95 |
| Spinach | 32 | 65-75 | 75 |
| Squash | 60 | 85-95 | 105 |
| Tomatoes | 50 | 65-85 | 95 |
| Turnips | 40 | 60-95 | 105 |
| Watermelons | 60 | 75-95 | 105 |
Important Note: the minimum and maximum temperatures below DO NOT mean your seeds will germinate at that temperature, but rather HAVE A CHANCE at germinating at that temperature. Ideally, you want to germinate your seeds within the optimum range.
Important Note for Celery: Celery has different day and night requirements. For best results, your daytime temperature should be around 85 (ºF) and your nighttime temperature should be around 70 (ºF).
Seed Germination Time for Hydroponics
The chart below shows the number of days your seeds will take to germinate at different temperatures. As the chart indicates, it becomes harder and harder to germinate seeds as they fall outside of their optimal range.
For example, the optimal range for lettuce germination is between 60 and 75ºF (see the chart above). If growing within this range, your lettuce seeds should take about 2 to 3 days to sprout. But if you’re trying to germinate seeds at 32ºF, it will take a whopping 49 days. Or, if you’re trying to germinate lettuce seeds at the other extreme, around 95ºF or 104ºF, your seeds are unlikely to germinate at all.
| Vegetable/Plant | 32ºF | 41ºF | 50ºF | 59ºF | 68ºF | 77ºF | 86ºF | 95ºF | 104ºF |
|---|---|---|---|---|---|---|---|---|---|
| Asparagus | Unlikely | Unlikely | 52.8 | 24.0 | 14.6 | 10.3 | 11.5 | 19.3 | 28.4 |
| Beans, Lima | Not Tested | Not Tested | Unlikely | 30.5 | 17.6 | 6.5 | 6.7 | Unlikely | Not Tested |
| Beans, Snap | Unlikely | Unlikely | Unlikely | 16.1 | 11.4 | 8.1 | 6.4 | 6.2 | Unlikely |
| Beets | Not Tested | 42.0 | 16.7 | 9.7 | 6.2 | 5.0 | 4.5 | 4.6 | Not Tested |
| Cabbage | Not Tested | Not Tested | 14.6 | 8.7 | 5.8 | 4.5 | 3.5 | Not Tested | Not Tested |
| Carrots | Unlikely | 50.6 | 17.3 | 10.1 | 6.9 | 6.2 | 6.0 | 8.6 | Unlikely |
| Cauliflower | Unlikely | Unlikely | 19.5 | 9.9 | 6.2 | 5.2 | 4.7 | Not Tested | Not Tested |
| Celery | Unlikely | 41.0 | 16.0 | 12.0 | 7.0 | Unlikely | Unlikely | Unlikely | Not Tested |
| Corn, Sweet | Unlikely | Unlikely | 21.6 | 12.4 | 6.9 | 4.0 | 3.7 | 3.4 | Unlikely |
| Cucumbers | Unlikely | Unlikely | Unlikely | 13.0 | 6.2 | 4.0 | 3.1 | 3.0 | Not Tested |
| Eggplant | Unlikely | Not Tested | Not Tested | Not Tested | 13.1 | 8.1 | 5.3 | Not Tested | Not Tested |
| Lettuce | 49.0 | 14.9 | 7.0 | 3.9 | 2.6 | 2.2 | 2.6 | Unlikely | Unlikely |
| Muskmelons (Cantaloupe) | Not Tested | Not Tested | Not Tested | Not Tested | 8.4 | 4.0 | 3.1 | Not Tested | Not Tested |
| Okra | Unlikely | Unlikely | Unlikely | 27.2 | 17.4 | 12.5 | 6.8 | 6.4 | 6.7 |
| Onions | 135.8 | 30.6 | 13.4 | 7.1 | 4.6 | 3.6 | 3.9 | 12.5 | Unlikely |
| Parsley | Not Tested | Not Tested | 29.0 | 17.0 | 14.0 | 13.0 | 12.3 | Not Tested | Not Tested |
| Parsnips | 171.7 | 56.7 | 26.6 | 19.3 | 13.6 | 14.9 | 31.6 | Unlikely | Unlikely |
| Peas | Not Tested | 36.0 | 13.5 | 9.4 | 7.5 | 6.2 | 5.9 | Not Tested | Not Tested |
| Peppers | Unlikely | Unlikely | Unlikely | 25.0 | 12.5 | 8.4 | 7.6 | 8.8 | Unlikely |
| Radishes | Unlikely | 29.0 | 11.2 | 6.3 | 4.2 | 3.5 | 3.0 | Not Tested | Not Tested |
| Spinach | 62.6 | 22.5 | 11.7 | 6.9 | 5.7 | 5.1 | 6.4 | Unlikely | Unlikely |
| Tomatoes | Unlikely | Unlikely | 42.9 | 13.6 | 8.2 | 5.9 | 5.9 | 9.2 | Unlikely |
| Turnips | Unlikely | Unlikely | 5.2 | 3.0 | 1.9 | 1.4 | 1.1 | 1.2 | 2.5 |
| Watermelons | Not Tested | Unlikely | Not Tested | Not Tested | 11.8 | 4.7 | 3.5 | 3.0 | Not Tested |
Frequently Asked Questions
Can you germinate seeds in hydroponics?
Yes, germination in hydroponic systems is completely doable. The only real difference is that hydroponic systems don’t use soil, so you’re usually starting seeds in some type of growing medium (such as coco coir).
Will transplanting be difficult after germination?
No, transplanting your seeds into a hydroponic unit isn’t difficult, but it does take a little bit of know-how. Try reading our seeds and seedlings guide to learn more.
Is this chart the same for soil?
Yes, this chart is the same — there is no difference between this chart and a soil temperature chart. Because a hydroponic growing medium (what you start your seeds in) is replacing soil in a hydroponic system, the temperature range should be about the same.
Where does this information come from?
This chart is also the go-to chart for soil germination and is listed on several academic websites. We used data from the University of California.