The effect of temperature on seed germination varies by species. The following table summarizes some useful data about the germination of different vegetable species under different temperatures.
The data presented can be used as a general guide, but there will always be exceptions.
In 2013, I had tomatoes germinate after two weeks of weather near 50ºF. One specific variety refused to grow until warmer temperatures were provided.
For the 2014 season, I acquired a surplus lab-incubator so I could provide germinating seeds with specific temperatures. With the incubator set at 25C, the tomato variety "Tiny Tim" all sprouted within four days. Another variety is still sprouting at 17 days later, with the first appearing at 14 days.
Each table entry is in format of "percent(days)". Entries with 80-89% germination are highlighted in yellow. Entires with 90+% germination are highlighted in orange. Entries that appear to be the best in terms of germination rate and shortest times are highlighted with pink.
The data presented can be used as a general guide, but there will always be exceptions.
In 2013, I had tomatoes germinate after two weeks of weather near 50ºF. One specific variety refused to grow until warmer temperatures were provided.
For the 2014 season, I acquired a surplus lab-incubator so I could provide germinating seeds with specific temperatures. With the incubator set at 25C, the tomato variety "Tiny Tim" all sprouted within four days. Another variety is still sprouting at 17 days later, with the first appearing at 14 days.
Each table entry is in format of "percent(days)". Entries with 80-89% germination are highlighted in yellow. Entires with 90+% germination are highlighted in orange. Entries that appear to be the best in terms of germination rate and shortest times are highlighted with pink.
| Crops | 32ºF | 41ºF | 50ºF | 59ºF | 68ºF | 77ºF | 86ºF | 95ºF | 104ºF |
|---|---|---|---|---|---|---|---|---|---|
| 0C | 5C | 10C | 15C | 20C | 25C | 30C | 35C | 40C | |
| Asparagus | 0 | 0 | 61(53) | 80(24) | 88(15) | 95(10) | 79(12) | 37(19) | 0 |
| Beans, lima | 0 | 0 | 1 | 52(31) | 82(18) | 90(7) | 88(7) | 2 | 0 |
| Beans, snap | 0 | 0 | 1 | 97(16) | 90(11) | 97(8) | 47(6) | 39(6) | 0 |
| Beets | 0 | 53(42) | 72(17) | 88(10) | 90(6) | 97(5) | 89(5) | 35(5) | 0 |
| Cabbage | 0 | 27 | 78(15) | 93(9) | 0(6) | 99(5) | 0(4) | 0 | 0 |
| Carrots | 0 | 48(51) | 93(17) | 95(10) | 96(7) | 96(6) | 95(6) | 74(9) | 0 |
| Cauliflower | 0 | 0 | 58(20) | 60(10) | 0(6) | 63(5) | 45(5) | 0 | 0 |
| Celery | 0 | 72(41) | 70(16) | 40(12) | 97(7) | 65 | 0 | 0 | 0 |
| Cucumber | 0 | 0 | 0 | 95(13) | 99(6) | 99(4) | 99(3) | 99(3) | 49 |
| Eggplant | 0 | 0 | 0 | 0 | 21(13) | 53(8) | 60(5) | 0 | 0 |
| Lettuce | 98(49) | 98(15) | 98(7) | 99(4) | 99(3) | 99(2) | 12(3) | 0 | 0 |
| Muskmelon | 0 | 0 | 0 | 0 | 38(8) | 94(4) | 90(3) | 0 | 0 |
| Okra | 0 | 0 | 0 | 74(27) | 89(17) | 92(13) | 88(7) | 85(6) | 35(7) |
| Onions | 90(136) | 98(31) | 98(13) | 98(7) | 99(5) | 97(4) | 91(4) | 73(13) | 2 |
| Parsley | 0 | 0 | 63(29) | 0(17) | 69(14) | 64(13) | 50(12) | 0 | 0 |
| Parsnips | 82(172) | 87(57) | 79(27) | 85(19) | 89(14) | 77(15) | 51(32) | 1 | 0 |
| Peas | 0 | 89(36) | 94(14) | 93(9) | 93(8) | 94(6) | 86(6) | 0 | 0 |
| Peppers | 0 | 0 | 1 | 70(25) | 96(13) | 98(8) | 95(8) | 70(9) | 0 |
| Radish | 0 | 42(29) | 76(11) | 97(6) | 95(4) | 97(4) | 95(3) | 0 | 0 |
| Spinach | 83(63) | 96(23) | 91(12) | 82(7) | 52(6) | 28(5) | 32(6) | 0 | 0 |
| Sweet Corn | 0 | 0 | 47(22) | 97(12) | 97(7) | 98(4) | 91(4) | 88(3) | 10 |
| Tomatoes | 0 | 0 | 82(43) | 98(14) | 98(8) | 97(6) | 83(6) | 46(9) | 0 |
| Turnips | 1 | 14 | 79(5) | 98(3) | 99(2) | 100(1) | 99(1) | 99(1) | 88(3) |
| Watermelon | 0 | 0 | 0 | 17 | 94(12) | 90(5) | 92(4) | 96(3) | 0 |
* The above data was taken from a report published in the mid-1980's. Author, affiliation, and publisher are not known.
** The above table was derived from experimental data. Certain logical inconsistencies exist due to crop failure or to bad batches of seed. They do not interfere with the overall interpretation.
What method are you using to germinate seeds in the incubator? I have a surplus hybridization oven that I've been using to start seeds, and I was pleasantly surprised to stumble upon your blog.
ReplyDeleteI've only tried red bell pepper and a few varieties of cherry tomatoes, but all of them have germinated within 3-4 days with >96% success (n>300).
I use wet paper towels in plastic food storage containers to maintain humidity, then incubate the seeds directly on the paper towels at 27C.