Climate

The geographical distribution area is identical to the drier zones of Mexico with a maximum precipitation of up to 1000 mm/year. These precipitations, however, are very unequally distributed over the year and mainly occur in the four summer months as heavy thunder showers. The rest of the year is dry. The majority of Coryphantha spp. grow in regions with less than 600 mm/year precipitation, i.e. dry and very dry zones, but the marginal areas of distribution are located in moderately humid regions.

Summer in the whole distribution area is very hot, but in the wintertime short cold periods and nightly frosts are not unusual, mainly in the north.

The climatic conditions are shown in Plate 5.

Coryphantha spp. are very well adapted to these conditions of climate. In winter they stop growing in order to withstand the dry-ness and cold. Growth begins again in spring shortly before or with the first rainfall.

In order to reproduce, Coryphantha spp. have two main strategies: either they flower very early in spring or summer so the fruits ripen within the same rainy period (a typical representative of these early flowerers: C. clavata). Or they flower in fall only, and the fruits remain dormant and ripen in the following spring when the seeds have a complete rainy season for germination (typical representative of these late flowerers: C. elephanti-dens).

Many Coryphantha spp. make use of both strategies and flower several times during the whole summer. In this case, some of the fruits ripen in the same summer, others towards spring.

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