Dictamnus albus · autumn flowering · out-of-season flowering · Karst Edge · drought stress

Autumn Flowering of Dictamnus albus

Observation of autumn flowering of Dictamnus albus in Slovenia's Karst region. Exploring the possible causes of out-of-season flowering.

30 October 2026

During October 2026 I noticed a couple of flowering plants of Dictamnus albus on hikes in the Karst region of Slovenia. This is not very typical for the plant as it usually flowers from May to June.

I encountered flowering plants in Škocjan Caves Regional Park and on the Karst plateau above the Karst edge. Firstly, I spotted just one flowering individual of Dictamnus albus at each location and I thought these might be only isolated cases. However, I later explored the area further, especially the plateau above the Karst edge and found numerous plants. Many were already flowering while others had only developed foliage. Autumn growth and flowering of Dictamnus albus therefore appeared to be much more widespread than I had initially suspected.

Flower buds of *Dictamnus albus* in the beginning of October

Alongside the flowering plants of Dictamnus albus there were also some other species that were in late bloom. Winter savory (Satureja montana) was in full bloom at the time. There was also a flowering individual of meadow sage (Salvia pratensis) and some individuals of Centaurea rupestris. So there were also other plants that were flowering very late in the season, which may suggest that the environmental conditions were such that allowed this to happen.

The summer of 2026 was exceptionally hot and dry in Slovenia. According to ARSO, it was the hottest summer recorded since 1950, with precipitation well below the national average. Many vegetative parts of the plants had dried up during the summer months. The autumn conditions have improved, rainfall returned and temperatures decreased. So it is possible that improved autumn conditions renewed growth of Dictamnus albus and other plants.

Autumn flowering of Dictamnus albus has been documented in Slovenia (2012), Austria (2022), and Hungary (2024). All three occurrences followed unusually warm and dry conditions, suggesting that summer drought, followed by improved autumn growing conditions, may contribute to flowering outside the species’ typical season.

Sources

Climate characteristics of last season - ARSO