Developing strawberry flowers are fragile things. They are susceptible to insect pressures, fungal pressures and climatic pressures as well. Even though our plants are categorically day-neutral, they aren’t immune to unfavorable temperatures, and one little spat of sub-freezing nights can decide that your season is over. That happened at the St Paul site this week. Notice the picture below of a healthy strawberry flower:
That bright yellow center is called the ‘receptacle’. It holds all of the seed-like achenes in place, and when fully developed it becomes the red, fleshy delicious part of the fruit. A yellow receptacle is a healthy receptacle. Now observe the flowers we saw on Monday morning:
Notice anything different? The receptacle is much darker. This means the blossoms froze during one of our colder nights, and won’t be recovering. Interestingly, our plastic low tunnels did not provide any protection from the cold this year; all of those plants experienced blossom freeze as well. This is unfortunate because our tunnels provided an extra 3 weeks of harvest last year! If I had to guess, I’d say the biggest difference is that last year’s low tunnels featured 4 mm thick plastic poly, while this year’s plastic from Dubois Agrinovation is a mere 1 mm. It seems that such a thin layer does not provide adequate infrared heat retention.
Whatever the reason is, black hearted blossoms always seem to beckon the end of the road for day-neutrals in Minnesota. Fortunately there were still immature fruit further along the development path than blossoms that weren’t affected by our low temps, so we have one more harvest left. But after next Monday it will be time to close the plot down. Stay tuned for a description of what that looks like!