My strawberries have just started fruiting and they have turned red quite nicely, except that the ends seem to be this brown/black colour which hasn't gone away.

They are growing in a home-made planter box (untreated timber) which is full of a mixture of top-soil and two bags of soil which was marketed towards growing strawberries. The ground is covered in straw and they get watered fairly frequently (it's raining quite a bit here at the moment despite being nearly summer).

They have netting over the top of the box to prevent birds getting in and I put slug pellets down last weekend as well as spraying the leaves with Derris Dust to keep the butterflies/caterpillars off them.

Any thoughts as to what might be causing this?


  • What's your climate like this time of year? Commented Nov 8, 2018 at 8:51
  • 1
    Down to around 10C (50F) at night, up to around 20C (68F) during the day. We've been having a few millimeters of rain here and there, although at the end of October we got 42mm (1.6") over a 5-day period. Humidity usually averages around 78% but has been a little higher this year as we've had a lot of overcast days and very few of the dry + hot ones so far
    – Dmihawk
    Commented Nov 8, 2018 at 19:01
  • Huh. That's interesting. Are these the regular size? Commented Nov 9, 2018 at 3:26

1 Answer 1


It looks like a pollination problem. The top strawberry has zippering and the bottom strawberry is under-developed on the blossom end. Cool, humid weather and lack of valid pollination may be the cause for each fruit respectively. The humidity, the cool weather, and the inhospitable weather for insects may be the pollination inhibitors. As for the zippering, high humidity and cool weather, as well as the variety of plant, are supposed to be contributing factors. Excessive nitrogen is also said to contribute to zippering. I looked for a source about strawberry zippering, but it only gave me links about tomatoes. The same principles probably apply, though.

Your fruits should still be edible, anyway. It's not caused by disease or pests.

Just a wild guess, but maybe adding some phosphorous to promote stronger, healthier blooms might help the plants have a better chance at pollination. Phosphorous is said to be less available (and more needed) in cool weather. Your soil may already have plenty, though (so be careful). Excess nitrogen may be why the fruits are small, though, if they're supposed to be larger. Wet soil can contribute to higher nitrogen availability. Nitrogen can compete with potassium (and potassium is said to play a roll in fruit size, but potassium is more available in cool weather already; so, again, be careful).

  • Thanks for all the really helpful feedback! :)
    – Dmihawk
    Commented Nov 9, 2018 at 5:47

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