How to prevent late blight

I was worried about my potatoes and tomatoes this year, but I have a few tricks up my sleeve that I think will help me to prevent late blight.

Tråg med jord och sättpotatis i tunnelväxthuset. Prevent late blight, trough with soil and potatoes in my polytunnel.

March: I chitted my potatoes and sowed tomatoes. I hope I can prevent late blight this year.


I felt really sad about the late blight situation last winter. It happens every single year. The potatoes get it first, but I can usually get a nice harvest of potatoes anyway since only the greens are affected by the blight. The tomatoes are not as lucky though. They rot when infested by late blight.

I was able to grow both tomatoes and potatoes in my garden this year, even though I was completely ready to give up on one of them this time around. All of my potatoes are in the small polytunnel now, while I grow my tomatoes in the beds outside and some of them in the large polytunnel. Maybe it's a bit backward, I know that most people grow tomatoes in their greenhouse and potatoes outside.


More about tomatoes: Tomatoes from sowing to harvest


Små tomatplantor under extrabelysning. Prevent late blight, tomato plants under a grow light.

I have been chitting the tomatoes in my cool hallway, and they have developed roots and greens. The tomatoes have been growing in room temperature under a grow light.


How to prevent late blight


I decided to only grow the varieties Orla and Sarpo Mira. These varieties are two of the hardiest ones out there. Orla is an early fast-growing potato. You can store these potatoes even though it's an early variety. Growing hardy varieties is a great way to prevent late blight.

I chitted my potatoes on soil/peat moss for a few weeks to get a head start. I planted them on the 22:nd of April in my polytunnel. We had a few cold nights and the potato greens froze. This slowed the potatoes down a bit. The greens look healthy now in June and the plants are starting to bloom, but I haven't felt any potatoes in the soil so far. I'm counting on getting a harvest around midsummer. It takes around 3 months until they are ready.

As you can see in the picture above, I'm not growing a lot of potatoes this year. I have three thin rows, that's all. But I'm going to plant more of them. I have another 7 lbs (around 3 kilos) that I'm going to plant in July. I'm going to fill at least another bed here in the polytunnel, and the rest will grow in one of the newly mulched beds outside. Planting potatoes in summer will give you a nice harvest of fresh potatoes later in the fall. What a luxury!


En täckodlad bädd med små plantor i. Prevent late blight, mulched bed with little plants.

I put my tomatoes outside together with corn. I covered the bed with mulch and silage. There are more tomatoes growing in other parts of the garden though.


The tomatoes

I decided to go for the variety Crimson Crush. This variety is supposed to be late blight-resistant, which is great of course! I have 20 plants outside now, grown from seed and companion-planted with corn in mulched beds that I watered with liquid soil probiotics. I will keep watering them with the liquid probiotic and might spray them later too.

I'm growing plenty of other varieties too, of course, no restrictions. I grow them in my polytunnels and outside, for example in the banana-shaped bed I have written about previously. I count on that most of them will be affected by late blight, I usually get a decent harvest anyway. I'm curious to find out how Crimson Crush will hold up though!


In conclusion...

I have to say that I'm really happy about growing both potatoes and tomatoes in my garden now. My garden would just feel empty without either of them. I'm growing some potatoes in a different spot too, so we won't be without tubers even though I don't have that much space for them in my polytunnel. The farm I usually hold classes at has a few new potato varieties I'm interested in trying next. I hope they will grow nicely!

So, the most important steps you can take to prevent late blight are:

  • Picking blight-resistant varieties.
  • Pre-seed the potatoes to get an early harvest before the late blight has time to attack.
  • Prepare the beds with soil probiotics.
  • Plant potatoes and tomatoes a bit further apart than usual.

I will write more about my results trying to prevent late blight soon!
/Sara Bäckmo



05. June 2019

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