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This about is the same scenario as my other question Do spring-flowering bulbs inhibit the growth of other plants? so I won't repeat the details.

In the past few days (last week of August), I have healthy-looking crocus leaves appearing months before they should be starting to grow in spring.

I thought the growth cycle was triggered by warming soil temperatures after winter, but this obviously doesn't apply here. The UK summer weather has been hotter than average, but otherwise fairly normal.

The bulbs were originally bought from a supermarket, not named varieties but labeled (correctly) by color, and definitely not as "autumn flowering crocus." In any case, autumn flowering crocus produce flowers before any leaves appear.

Any ideas what might be the cause of this?

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  • hotter than average? Not in the London area it hasn't been other than a 4 day heatwave mid July - daily temps have been around 20degC only out of the sun, quite a bit below average. But perhaps where you are this is not the case?
    – Bamboo
    Aug 23 at 21:33
  • I agree it was a cold spring, but the Met Office surveys give June as 1.2C above the long term average and July as 1.5 above. I would guess August will be similar. FWIW I'm in Derbyshire.
    – alephzero
    Aug 23 at 21:57
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Long term averages refer more to climate rather than weather. Spring bulbs respond quite strongly to temperature cycles, so a hot spell followed by a cold or cool spell followed by a warmer (but not hot) one. In the London area and other parts of the country around 4 years ago, daffodils were blooming in early November. That year, we had an usual cold snap in September with unseasonably low temperatures, followed by a warmer spell, which fooled the daffodils into thinking it was time to flower. Apple trees were also flowering at that time..

I don't know what your local weather has been like this year, there's been quite a bit of variation round the country, but almost all parts of the country had a heatwave mid July, followed by much cooler, gloomier, wetter weather which has more or less continued. In early August, I recall flicking the heating on for twenty minutes to take the damp chill off indoors, but since then,it has got warmer at around 20degC out of sunlight, but still below the usual August temperatures which in the London area range between 25 to 30 degC, with relatively warm nights, but we've also had cool nights. These weather events may have fooled your crocus into flowering now, but they may just stop and not actually flower, just leaving the foliage in situ.

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  • That sounds plausible, but if bulbs really are so "trigger happy" I'm surprised this doesn't happen more often.
    – alephzero
    Aug 26 at 2:42
  • It doesn't often happen, but has become a little more frequent due to ever more variable conditions likely due to climate change ramping up
    – Bamboo
    Aug 26 at 14:22

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