A matter of timing?

1 - Flowering spectra observed in 72 alpine plant species in the summit area of Mt. Glungezer (2600 m, 600 m above treeline, Tyrol, Austrian Alps).

1 - Flowering spectra of 72 alpine plant species.

Variation in phenology

Alpine floras are famous for their flower richness. In temperate alpine regions, this is because of the short growing season causing very pronounced seasonal peaks of flowering. In the central Himalayas more than 70 % of all species flower during mid July, or in the alpine zones of temperate mountains by the end of July. In the tropics, too, pronounced seasonal cycles can narrow the flowering period for most species to a few months.

2 - Few plants flower when there is still snow.

3 - Peak flowering in summer

Snow cover as a limit for reproduction

Snow cover and time of snowmelt have been suggested as the principal factors controlling the distribution, the flowering phenology and seed set in alpine species. This control may be effected directly by determining the length of the growing season or indirectly by regulating soil moisture or low soil temperature affected by melting water.

Number of species in plots differing in their snowfree period (Hokkaido, northern Japan, 1900 m)
Plot	Snowfree period (days)	Total no. of species	Shrubs	Forbs	Graminoids
A	100	36	12	16	8
B	85	33	10	13	10
C	70	24	8	9	7
D	60	21	6	9	6
E	50	5	2	0	3

4 - Fruit set from pollinator visits in the alpine dwarf shrub Rhododendron aureum (Ericaceae) in the Taisetsu Mts. in Hokkaido, northern Japan (1900 m), in quadrants along a snowmelt gradient (Kudo 1993).