The annual aridity at summer’s end did not prepare us for the surprise found on one hill in the desert plot in the Botanical Garden, covered with the purple blooming of the autumn squill (Scilla autumnalis). The autumn squill is a Mediterranean species, growing naturally on the kurkar (Calcareous sandstone) hills of the garden.
This is a small bulb plant (geophyte), with a 10 cm high inflorescence stem. It blooms twice in the season, to increase the probability of reproductive success: the first round is on a fixed date when the days become shorter, responding to the light cue; and the second round is after the first effective rain, responding to soil humidity as a cue. This strategy guarantees seed production at least once, even in cases of drought.
The unusual flowering timing of the autumn squill, alongside that of a few other geophytes, marks the end of summer and the beginning of autumn. The ability to bloom in this harsh season is based on good preparation, achieved through acquiring photosynthesis products in the green leaves during the previous winter. These metabolites are preserved as starch in the bulb and are exploited in the autumn.
The advantage of flowering at this time lies in the lack of competitors for the pollinators, due to the low number of flowering species in this season. Among these one can find in the Botanical Garden the following: small-flowered pancratium (Vagaria parviflorum), Urginea undulata and Allium tardiflorum.

Photo: Gavri Sion

Allium tardiflorum, Photo: Gavri Sion