There are only 3 things you need for the seed to germinate: a healthy seed, water, and the right temperature. Healthy seed is something we can’t really affect. We can collect them in time and store them in a dry place, but other than that we can’t really be sure the seed will germinate. We have even less influence when we buy seeds. The quality of seeds that are offered to hobby gardeners is getting worse every year. A few years back our seed packages had to have a percentage of the germinating seeds. I remember how back in days that percentage was around 95%, then 90% and then it mysteriously disappeared from the packages. Now the only thing the package needs to have is the year when the package was sealed and the expiration date. This actually doesn’t tell us the year in which the seed was harvested, and we don’t really know how old the seeds really are. The change in the seed germination was obviously getting worse. Before you could buy one small package of carrots, and you’d get lots of baby carrots, and now you need a big package to get a few seedlings.

This is why we started buying bigger packages and sowing seeds way thicker than we actually should. It’s easier to thin out the plants than to sow 3 or 4 times to get the needed amount of seedlings. But even if we have perfect seeds that’s no guarantee we’ll have lots of seedlings. Not if we do not have one of the most important things: the right temperature. If we don’t manage to get the perfect temperature needed for germination, we won’t have any seedlings, and the temperature is actually the biggest issue during winter.

Some vegetables like peas are really easy when it comes to temperature, as soon as the temperature is over 10°C (50°F) they will start growing without problems. They will actually cause more problems if the temperature is too high than in low temperatures. But others, like tomatoes, peppers, eggplants, cucumbers, and even some varieties of lettuce, will not germinate without summer temperatures. That can be a real problem during winter because we don’t heat our house to summer temperatures. Most of the houses are heated to temperatures around 23°C (73°F) and this is not warm enough for most of the heat-loving vegetables. Because of this germination can be slow and poor, and if the seeds aren’t perfect, we could be left without any seedlings.

The exact thing happened to me this past two seasons. I’ve sown a bunch of seeds and I had very poor results. Especially with the tomatoes and peppers. Both were germinating very poorly, and the seeds that actually germinated gave poor seedlings.

This is why I was forced to buy my seedling this year, and I’ll have to come up with some kind of heated greenhouse inside the house for next year. Still, there’s one time of the year when the temperature is not a problem for seedlings: summer.

It’s unbelievable easy to get the seedlings to germinate during summer. Garden germination can be a problem due to the lack of water, but when the seeds get enough water, the germination even in the garden will be fast. The seedlings will grow even twice as fast in the summer than in the spring. 

My balcony is the perfect example of the effect of temperature on germination. During the spring our temperatures were well below average. Usually, our garden is a perfect germination spot for all of the vegetables, except for tomatoes and peppers. But this year things were different. I’ve sown dozens of trays with cabbages, lettuces, cucumbers, carrots, beets, and zucchinis. 

Eventhough I had my seed trays in the sun most of the day and wrapped in plastic wraps to help them keep the heat, germination was really poor. Many of the trays stayed empty, whole varieties didn’t germinate at all, and the ones that did took 14 to even 28 days to germinate. This was really frustrating because I kept filling the trays and nothing seemed to happen. I had no room to keep the trays indoors, and nothing was happening outside.

This is why I was skeptical about the summer sowing. I knew that the trays would have the perfect temperature on the balcony, but still, the poor spring conditions made me doubt. I placed them outside, watered them every evening, and kept them in the shade during the hottest period of the day. I have two bamboo blinds that I lower half of the way to keep the direct sun away from the trays. The direct sun dries them in 2 minutes, and this way trays are wet during the whole day. 

In these conditions, the air temperature in the afternoon was around 33°C (91°F) and morning temperature never dropped under 25°C (77°F). 

After just 4 days the seedlings started appearing and opening their leaves like little umbrellas. After less than a week I already had all of my lettuce out, soon joined the kale and chard and last onions and leeks started showing up. Flowers are still not out, but I can see the soil lifting, so I’m expecting them to germinate really soon.

Just 4 days is such a short time that I was honestly surprised. I would never say that I’d have seedlings so soon. 

Again the seed quality is very much visible, some of the trays have a couple of seedlings, while others have a bunch of seedlings, but I was prepared for this. The trays with one or 2 seedlings will be transplanted as is, and the ones that have more seedlings will be thinned out. I’ll cut the extra seedlings(mostly chard and lettuce) and use them as microgreens in a salad. This way they won’t go to waste and I’ll have just the right amount of seedlings.

So I guess I’ll have to give my seedlings the same temperature in the winter as they had during the past week, and they will be happy. If only I had any idea how to do it, all the problems would be solved.