Onion sowing 2025: germination and emergence require attention

Now that almost all the onions have been sown, the exciting period of germination and emergence follows. Kees Jacobs urges growers to monitor the onions closely during this period. "There are all sorts of things going on now. Do you need to irrigate? When to burn? And what does the bean fly do? Now it's time to pay attention."

"I think 95% is already in. Maybe even more." Kees Jacobs saw the onion sowing machines working overtime in recent weeks. "It's not surprising, because the soil dried out very quickly and especially on clay soils you can easily miss the best moment for seedbed preparation. And of course everyone still has the previous two seasons in mind. It's been a long time since we could sow in March." Many growers took for granted that the soil was actually too cold, the onion expert from Syngenta Seeds saw. "In many places that is still the case. There are also growers who waited because of that. And I have also spoken to growers who postpone sowing for a while because they expect the seed to dry out. But most growers thought the conditions were too good to let go."

Glass plate
For the coming period, the motto as far as Jacobs is concerned is mainly 'count and watch'. Initially, of course, to follow the germination and emergence. "Not all the seed will be in solid ground", Jacobs estimates. "And certainly with primed seed, that should not take too long. So it will be necessary to irrigate here and there. You can already see the reels turning in the fields." To get a good picture of the emergence, Jacobs advises to regularly, at least twice a week, count the germinating seeds and already emerged plants on a few meters. "The best thing is if you always do that on the same meters, but that is of course difficult. But counting in different places is still better than not counting."

According to the onion expert, the trick with the glass plate is the best method for timing the burning spray. "Under that plate, the onions will germinate a little earlier because it gets warmer and stays a little more humid. As soon as you see the seedlings appear there, it is time to burn."

Bean and onion fly
Due to the early sowing and the (hopefully) rapid emergence, the onions will probably be faster than the onion fly on many plots this year. Jacobs qualifies that a bit: "The onion fly will of course return and the larvae will eat the plants, but they will not fall over as quickly. But controlling the onion fly remains important, because feeding spots can be entry points for fungi and bacteria. And if you do not tackle them, you will get population build-up and therefore bigger problems next year."

The bean fly will probably be a bigger problem than the onion fly this year, the onion cultivation advisor expects. "The bean fly usually appears in the first half of April and is attracted by germinating plants. If you have not applied granulate when sowing, you only have the pyrethroids at hand to intervene." Jacobs thinks it is a positive development that more and more onion growers are having not only the onion fly but also the bean fly monitored. "Then you know when the flights are and you can respond to them if necessary."

Area shrinking
For Syngenta Seeds itself, the onion season already started with the sales activities in the autumn and they went well, Jacobs knows. "Our new red variety Allurion was already sold out at the end of October. Due to the favorable pricing, there was a run on red onions. But you have actually seen for years that the area of ​​red has been growing. Consumers and processors appreciate the taste and the color."

Estimating the onion area for 2025, Jacobs thinks that there will be a slight net shrinkage. "Many seed companies, including ourselves, have had problems with seed production due to mildew infestations on the propagation plots in France. As a result, I expect the area of ​​red to remain approximately the same. And for yellow, I expect a shrinkage of around 5%. Fortunately, we had stock ourselves and our sales have increased by tens of percent. So this year, there are a lot more growers who are getting to know our beautiful range of varieties."