The differences between neighbouring populations are gradual. This is a common feature in biology. The term clinal variation is often seen in biological literature. Achillea lanulosa can be propagated vegetatively. The experiments showed, that each ecotype performed best under condition resembling its natural habitat closest.
Clinal variations depend on the activity of a large number of genes.
Despite habitat-specific factors, seasonal factors, too, play an essential role in the selection of optimally adapted races. Following the winter rains, plants flowering in spring develop rapidly. Their shoots remain small. Plant flowering in autumn develop an extensive root system as an adaptation to the dry soil, a dense rosette of leaves, and tall shoots. These features of the plants are stable even under standard experimental conditions.